Fatal in Ozz

[earthbnd misfit]

Witnesses to a fatal gyrocopter crash in South Australia's east say it looked as though the pilot fell out of the sky.

The 60-year-old man from Victoria crashed his aircraft at the Lameroo Airfield just before midday and died at the scene.

Investigators say the crash may be due to pilot error.

One witness has told the ABC the man was an experienced pilot.

Anymore news on this?

[barnstorm2]

Very sad. My condolences to all family and friends.

.

[barnstorm2]

http://www.heraldsun.com.au/news/victoria/man-dies-in-fiery-crash/story-e6frf7kx-1111114843841

no that was Pauls crash in November 10, 2007


.

[C. Beaty]

As nearly as I can tell from the twisted wreckage: low rider, rock guard but without proper horizontal stab.

[Resasi]

Condolences to family and friends.

Seems to be a remarkably intact rotor.

[HobbyCAD]

Paul was with a pax, Chucks picture looks like another crash of a simple Bensen-type gyro.

Pic in newsclip of Paul's crash shows brushfire around the wreck.

[Murray Barker]

I have attached a photo of the gyro which was involved in a fatality yesterday.

The Pilot was NOT experienced with less than 100 Hrs.

The investigator in charge has only just arrived on site so a little bit early to say "pilot error" or otherwise.

As you can see by this photo it is what i would call a very high thrustline with no effective HS.

An accident waiting to happen.

I am extremely p*ssed off to see a machine like this permitted to be registered.

[Greg Mitchell]

Murray,

Very sad indeed and I agree with your sentiment.

As President of ASRA, why not lobby for change to the building code/requirements.

I am sick to my stomach, when I see gyroplanes configured like this, when we have the ability to build out this type of "accident waiting to happen".

Part of the problem is we have some ASRA TA's and Instructors who would suggest that aircraft is near CLT........say no more!

To suggest always pilot error, when a HTL gyroplane bunts, is simply wrong.
The pilot may be in error but only because he or she purchased said "accident waiting to happen."

I am not suggesting a cause to this accident. I am only venting my frustration at to many deaths over such a short time and the apparent need to always blame the pilot.

Sad day indeed.

My condolences to the family and friends.

[Murray Barker]

Thanks Mitch. There WILL be changes.

[bpearson]

I'd be very careful before you try and legislate against free choice.

[Aussie_Paul]

Possibly pilot error in choosing dangerous gyroplane geometry.

Aussie Paul. :)

[Graeme Monro]

I'd be very careful before you try and legislate against free choice.

Very true Mr. Pearson, people should always have the freedom to choose to kill themselves and destroy the sport of gyroplane flying for everyone in this country.

Graeme.

[Semler]

I have attached a photo of the gyro which was involved in a fatality yesterday.

The Pilot was NOT experienced with less than 100 Hrs.

The investigator in charge has only just arrived on site so a little bit early to say "pilot error" or otherwise.

As you can see by this photo it is what i would call a very high thrustline with no effective HS.

An accident waiting to happen.

I am extremely p*ssed off to see a machine like this permitted to be registered.



Amazing! by the sounds of it then there should be alot more gyro's in Oz falling out of the skies.

And Im Sure there will be even more People pissed off when there beloved machines are worthless when it comes to selling if you believe that they shouldn't be registered.

I look forward to the report on this investigation, There are many reasons why a gyro can fall out of the sky.


Trent Semler

[Murray Barker]

Legislate against free choice? What crap.

YOU ring up his wife and tell her we know this type of gyro was a deathtrap but we don't intend to do anything about it now or in the future.

What we have here is a novice pilot buying and flying a gyro unaware of the inherent instability of a design and dieing as a result.

As I said,there will be changes.

Paul,your input will be sought at a later date.

[Murray Barker]

Trent, that's just the problem! THERE ARE lot of gyros falling out of the sky with this configuration. How does 3 in the last few months sound!!

When was the last time YOU had to sit down at a crashed gyro sorting thru twisted parts with human blood and tissue still evident from someone you most likely knew???

[bpearson]

Legislate against free choice? What crap.




So you intend to outlaw people riding a 'certain type' of horse? Or ban surfing in all but the calmest conditions? What about homebuilt motorcycles that are unstable?

The 'ruining our sport' argument is always brought up but the only people who will ban gyros are the legislaters who feel the need to nanny the population. Carry on down that road and you will end up living in a very dull country.

[Semler]

When was the last time YOU had to sit down at a crashed gyro sorting thru twisted parts with human blood and tissue still evident from someone you most likely knew???

Never Murray, And I Really feel For Kevin and Co.


Are your saying that a CLT Machine will not unload in Flight? **(Edit Sorry EI-Gyro I wasn't too clear there,)** If a CLT gyro Unloads what will it do With power on????? and with an engine failed what will a CLT gyro do when unloaded.

[EI-GYRO]

Of course it will. Just wont do a forward flip and kill the pilot.

[HobbyCAD]

Murray and Greg,

I strongly differ with your "kneejerk" reaction of wanting to legislate the problem away. The correct answer should be educate it away. Don't force rules upon us, we already live in the most overregulated country in the world !!

If you are p!ssed off because such a gyro was registered, may I then ask, where were the technical inspectors to advise (educate) the man otherwise.

You simply cannot ban everything that is a perceived problem !! You cannot outright ban the old legacy-type machines. There are a gazillion Bensens and KB's flying "all fine and dandy" out there.

Could you inform us more on this gyro that crashed? What make was it? Was it a kit, or a plans-built, or a "first-of-type", an imported machine, an Australian machine? Was the pilot the builder, or an unexperienced buyer? These would all be interesting information

[bosca]

I agree with Murray 100%.I cannot believe those who talk about freedoms in this circumstance.We have seat belts,airbags etc to save our lives and it would only be a fool to suggest that our freedoms are compromised.
The best way to keep CASA of our backs is to have a good saftey record.It is vivid in my mind that some in the legal proffesion in Queensland for example wish to ban Gyros.
Is this what you want? Then carry on with your ignorance!!

Kym Caskey


History is phylosophy taught by examples!!!!!

[HobbyCAD]

Kym, you can't compare regulatory change with seatbelts and airbags in cars.

The system works, albeit a bit overregulated already. It's not the system that failed, it's the people in the system. If we have to take in on the chin from CASA because people failed the system, then so be it, but don't change regulation that has been working fine in the past.

[bosca]

Are you serious Hobby,dead people =success.Please ,please no more.This is the system that we are assuming is HLT without proper horizontal tail
Kym Caskey,

[bpearson]

Ban unicycles because they are not the most stable form of cycling. People should NOT be allowed to ride them..they must be stopped!!!

[bosca]

Oh,I presume you have a nack of spinning some Irish Jokes bp.
Kym.

[Heron]

Against more laws and rules or all of them?
Where do you against guys draw the line?
And . . . are you in charge of drawing or you are on the receiving end of rules?
Can´t register or fly if you don´t get educated on the problems at least, after that it is your choice but I doubt your family will be cheering on the stands . . .
Yeah . . .go ahead, pull the trigger . . .it may be empty . . .stupidity kills more people than wars.
Heron (learn to obey and you can command)

[RotoPlane]

I believe there is room for common-sense regulation in a free society. Anyone that has knowledge of gyroplane stability would not think of flying that pictured gyro, only those that are unaware would fly such a machine. Understand….I hate big-brother laws….including seat belt laws. Outlawing machine types that have known stability flaws is simply using common-sense to protect the unaware.

[brett s]

I'm glad we have the freedom in the US to build & fly what we like, even if dangerous.

What I don't care for are companies selling dangerous kits, either with known design flaws or substandard parts.

But that's also part of the deal with experimental aircraft, you have no assurances of anything - it's buyer beware, you must do your homework.

Unfortunately that also means we get a demonstration of Darwin's theory every so often - it's the price of having that freedom, some will inevitably make poor choices & they can be fatal.

[barnstorm2]

Ban unicycles because they are not the most stable form of cycling. People should NOT be allowed to ride them..they must be stopped!!!

Unicycles are (typically) designed to be unicycles and those that buy unicycles know what behavior to expect from them.

What we are talking about here are not a KIND of aircraft but a FLAW in design.

A proper analogy would be banning Unicycles that have a bomb embedded in the seat that goes off killing the user when they make a common mistake while riding the unicycle. A mistake that is dangerous but typically not always fatal when made in unicycles without the bomb.

PPOs are the result of a DESIGN FLAW.

There are NO DESIRABLE traits gained from having gyro susceptible to PPO.

.

[gilgsn]

Hello,

Consider this about the regulation/registration issue: That a pilot wants to build a HTL/no-stab gyro knowing it is dangerous, fine. I think he should be warned, but not stopped. The problem is that when a dangerous machine is built and registered, it can be later sold to someone else as a safe machine. Not to mention two-seaters. When passengers are involved, it's an all new ball game.

You can't compare the issue to banning unicycles! Unicycles do not carry passengers, they do not fly over other people, and they are very simple machines to understand. As to horses, they have a mind of their own. Everyone knows the ocean can kill you fast; apples and oranges..

I am very much against rules. However, when a government agency inspects a machine and have you stick numbers on it, I think it should be reasonably safe. Otherwise, prohibit the builder from selling it to some unsuspecting fool who's going to leave a widow and four kids.

Gil.

[PTKay]

But that's also part of the deal with experimental aircraft, you have no assurances of anything - it's buyer beware, you must do your homework.

Unfortunately that also means we get a demonstration of Darwin's theory every so often - it's the price of having that freedom, some will inevitably make poor choices & they can be fatal.

Yes, Darwin works perfectly in the jungle and in the desert.

But I thought we are in a civilized world, not in the jungle...

Caveat emptor. This stupid anglo-saxon rule opens the door for all kind
"snake oil sellers", for which US is so famous.

But this rule is being recently abandoned even in the UK.

[bpearson]

Yes, the lawyers have totally f***** the UK. Looks like the rest of the world is embracing socialism too.

The state knows best!

[Vance]

I feel that a thread about loss of life that the survivors will probably read may not be a good place for the heated debate about rules and design.

I feel commiseration with the friends and family of this pilot.

Thank you, Vance

[Murray Barker]

Hobbycad,There seems to be some sort of notion this is an isolated case.The predominent theme in single seat gyro accidents in this country is powerpushovers.

To say gyro operation in Australia are over regulated is ludicrous. At present gyro's are controlled by a non government body of gyro enthusiasts that allows anyone to build a gyro and fly it basically anywhere he or she likes with few rules.

We wouldn't register a gyro that used plastic bolts so why would you register one with a 12 inch offset in the thrustline?.

To say we are going to outlaw Benson type gyros is stupid.It seems one of the biggest problems here is ignorance. People who happily tell you they have a "Benson' gyro but think its OK to have a 72 inch prop on the thing.

This argument is not about some 5000 hour pilot chasing cows in the middle of nowhere in a HTL machine fully aware of its limitations through experience.

[C. Beaty]

Hobbycad,There seems to be some sort of notion this is an isolated case.The predominent theme in single seat gyro accidents in this country is powerpushovers.The same is true in the US although the chorus of hand wringers would have one believe it is entirely due to lack of training.

And in a sense it is because many CFIs are not educating their students about the danger of flying a rat trap.

[HobbyCAD]

Murray,

Was this guy trained? Was he part of a group of enthusiasts? Not referring to ASRA membership, asking if he was part of a group of guy's flying gyro's.

I'm still of the opinion that education is the way to solve the issue.

[RotoPlane]

I'm all for educating those that are unaware of stability issues in lieu of regulations, but history shows that is not a practical option. Shoot….even some CFI's do not get it. So to help prevent unnecessary grief and family heartbreak, I'm all for a common-sense approach to minimum stability rules for gyroplanes.

[PW_Plack]

When I took ground school for the Private Pilot in airplanes, there was a chapter on weight and balance, and a chapter on aerodynamics. People still do stupid things, but at least they're taught what not to do, and have to pass a test on it.

When the NTSB investigates a fixed-wing accident, it always looks into how the mass of passengers, baggage and fuel was loaded with regard to CG, and how it might have affected stability, including how that balance might have shifted as fuel was burned.

Then, I look in the FAA's approved Rotorcraft Flying Handbook, and see presented the idea that rotor thrust vector ahead of CG is just another apparently acceptable way to arrange the forces for equilibrium. When there is a crash, the NTSB usually sends an unqualified team, and settles for a whitewash, "pilot failed to maintain control of the aircraft."

Education can work, but only when the teachers know the subject matter.

[bpearson]

Look at what you might get. Once you start stating that a machine should be built 'this way' you open yourself up to all sorts of issues. You are in effect saying the machine is safe. It no longer is experimental and when something goes wrong dependants will come looking. The authorities will decide action needs to be taken and before you know it you will all be allowed only to fly $100,000.00 factory built gyros.

This is what happened in the UK with the Air Command. We now have a de-regulated class where you can build a plane out of meccano if you wish and because the CAA have no input to the regulation of it there is no liability.

Be very careful what you wish for.

[bosca]

Vance,with due respect these issues are often best delt with when there is a passion and a will. In this respect /s it is the result of fatal accidents.
bp,can see your point,however we cannot sit on our hands.With my little knowledge of gyro design I myself see what are bad designs as far as thrust lines and in many cases are short coupled.That is the tail feathers are too close.Look at general aviation the horizontals are in many cases well aft and for a reason. Some are people who are my friends.
Kym Caskey.


History is Phylosophy taught by examples.

[Fl90]

I would have flown it.

I would have run it through the envelope test laid out for me in an old publication.

I would not have flown it outside the limits found in the test.

I might have died flying it.

I might have died getting dressed to fly it.

If I was told that flying it was forbidden, I would have made a point to fly it.




My condolences for friends and family. I hope any dependants are cared for, well.

Good day to all.

Phil

[Aussie_Paul]

.....an HTL gyro IS less safe than a CLT gyro given the same operating conditions.

The battle continues... In approx 1990 I was President of ASRA and Mceagle was vice president as well as chairman of the ASRA two seat committee. We had mandatory H/Stabs included in the operations manual. Remember knowledge was limited back then, but basic tail feathers improved my Air Command as well as most gyroplanes. A couple of presidents later, who did not believe in H/Stabs had the requirement removed. I had to put up with lots of criticism when I opened up discussions re CoM and thrust line relationships.

PWBlack said
Education can work, but only when the teachers know the subject matter.

Progress is slow BUT progress is happening. One of the worst problems we (the gyroplane community) have is people in authority making or influencing aerodynamic rules and regulations who do not understand basic aerodynamics, let alone gyroplane aerodynamics.

Oops, sorry. Getting on my old soap box again!!!!:yo:

Aussie Paul. :)

[Murray Barker]

Total hours for the deceased pilot were around 20 hours dual and 40 solo.

Paul is absolutely right. We still have people including instructors that tell students horizontal stabilizers are dangerous and not required on gyro's.

I am sure the "don't tell me what I can fly" mob in Australia will be even more dismayed if a government agency DOES take over the control of design, registration of gyro's and licensing of pilots due to the appalling safety record.

[Aussie_Paul]

I was converted by my "1999 Norms forum" enemies :wave: who became close friends when they were able to logically convert me to correct aerodynamic knowledge. Fortunately I have an open mind and, although I debated strongly, I soon realised that I was wrong in my understanding of gyroplane stability.

After that occurred, in approx. 2000 I refused to train anyone that had a HTL gyro unless they, with the offer of my help, modified it. I only had one whom I could not convert with appropriate explanations. He went elsewhere for training and I believe ended up dead. I slept at night.

Aussie Paul. :)

[Aussie_Paul]

Paul is absolutely right. We still have people including instructors that tell students horizontal stabilizers are dangerous and not required on gyro's.


H/stabs are a start BUT gyroplane stability is the most important item on the agenda, not whether H/Stabs should or should not be mandated.

WHY do we allow people to hold certificates and positions of power when they do not posses the knowledge????

If I can be taught why can't much more clever people than I be convinced?????

Aussie Paul. :)

[Semler]

Murray,

I don’t believe any sort of change to the regulations are needed as it will hurt Us gyroplane operators, Instead of regulatory change why not have change by education, E.g. When a student signs up for their membership and receive their student packs they receive a memo of what the Board and ASRA as a whole perceive as a safe and stable Gyroplane.


I Must say that I have not flown in a truly CLT machine, the closest I’ve came to was my old Bensen style gyro and I loved it for its stability. I now fly a very high Thrustline machine (I would say even higher than G102), Which I also love.
I have been taught and drill into by my instructor about how to fly my machine appropriately and to always fly within my abilities and the conditions of the weather.

As with all types of flying, the machine will only do what the nut behind the stick tells/allows it to do.


If ASRA chooses to have a “Stability Reform” I just hope they consult their members before any hands are dealt.


Well Im going to climb back into my hole.


Regards,

Trent

P.S.
Does anyone even know if this crash was related to the high Thrustline design? Or was it mechanical or medical?

Oh and for anyone thinking im anti CLT im not and im currently in the early stages of building a new gyro that will hopefully come out close to CLT.

P.P.S.
We have some fantastic people that Design, Build and supply Parts for gyroplanes in Australia I hope that this does not deter them from continuing on helping others.

[Murray Barker]

"Hurt us gyroplane owners"???? The pilot of the crashed gyro is as hurt as it gets.

Trent are you saying that for a few hundred $$ and a bit of work modifying a gyro to make it safer is not worth it?

It cost no more to build a CLT gyro in the first place. What could people possibly have to complain about?

At least three manufacturers in OZ already make CLT gyros.

The gyro involved in this accident had at least two rotor strikes on the tail at different angles and the third strike severing the tail boom.Classic PPO.

[Semler]

I havent been around gyroplanes for long and im here for education, So i will take you word that its a classic PPO, ( I did notice on the pictures of the G102 on the Tv that the rotors were both bent upwards... is that a tell tail sign of PPO/Rotors unloaded in flight?)

BUT, Before you write off this accident to what you see as a poor design, can you answer me this, lets say hypothetical that someone is flying along in their HTL gyroplane and suddenly their engine fails and panic strikes and he pushes forward and goes negative. would the signs of a classic PPO look the same as someone that goes negative?

Cheers,
Trent

[birdy]

To say we are going to outlaw Benson type gyros is stupid.It seems one of the biggest problems here is ignorance.
Your spoton Muz.
And im backn you all the way.

Befor you can fight ignorance/educate is to first get the persons attention.
Refusen to register a machine thats dangerous will get their attention. Maybe theyll do a bit of dign and educate themselves as to why the machine wont be registered. Then theyll at least know, wether the CFI tells them or not, that a dangerous design is just that , dangerous, and he'll know why.
No longer ignorant.

If he thinks, "f&^$ um, i can fly it", then at least the ASRA mob will sleep better at nite known that the bloke knew better. Just chose to ignor the warning.

Comparen an unstable machine to a unicycle, horse, wave, bull, car without airbags bla bla bla is crap.
The unicycle, horse, wave, bull, car without airbags bla bla blas generaly dont kill you on their first attempt.
An unstable gyro will.
I know of alot of people who have hada stack off the unicycle, horse, wave, bull, car without airbags bla bla blas, repeatedly, and are still ere.
Iv never heard of anyone surviven a PPO.

One thing thatll never go away is sum peoples gullability.
Advertise it for long enuf and sumone will eventualy buy it.
But if they cant register it, theyll want to know why.
Id rather have to deal with a pissed off new [ unstable] gyro owner than be speakn to the family.



BTW, a machine like the one pictured wouldnt faze me abit, coz thats wot i grew up on, but id never buy it, coz its inefficiant and heavy, and i know better.

[bpearson]

[I]

Comparen an unstable machine to a unicycle, horse, wave, bull, car without airbags bla bla bla is crap.
The unicycle, horse, wave, bull, car without airbags bla bla blas generaly dont kill you on their first attempt.
An unstable gyro will.
I know of alot of people who have hada stack off the unicycle, horse, wave, bull, car without airbags bla bla blas, repeatedly, and are still ere.
Iv never heard of anyone surviven a PPO.



I wasn't comparing any of those to a gyro.....I was comparing the rush to regulate gyros compared to other pastimes.

I don't know the legal system in Australia but you should be very wary of amateurs starting to issue regulations. Like i said....if someone says 'this is safe' then the lawyers will come after you when something bad happens! We came very close in the UK to the authorities banning gyroplanes. Now...with single seater dereg class the CAA have no input therfore no comeback. They couldn't care less about your safety....thats your business.

[C. Beaty]

The gyro involved in this accident had at least two rotor strikes on the tail at different angles and the third strike severing the tail boom.Classic PPO.From the distance between rotor strike marks, a close approximation can be made to tumble rate. It closely follows the calculated tumble rate based on propeller thrustline offset and machine moment of inertia.

A sheet metal tail leaves unmistakable evidence; a gyro with foam/fiberglass tail less so.

[robby986]

I met this fellow at, of all places, my dentist a couple of weeks ago. He was one of the other dentists. He was told that I was a fellow gyro pilot and came in to my dentists surgery for a chat. He was telling me about this trip and what he was going to achieve. He was excited to know that I was based at Ballarat.He planned to fly over and see me. I had a dental appointment today and was told the news of his death by my dentist. It was a very gloomy couple of fillings. No funeral date as his body is being held in South Australia while investigation is underway. short news report in link. http://www.abc.net.au/news/video/2010/05/02/2888254.htm?site=centralvic&section=video

[robby986]

I met this fellow at, of all places, my dentist a couple of weeks ago. He was one of the other dentists. He was told that I was a fellow gyro pilot and came in to my dentists surgery for a chat. He was telling me about this trip and what he was going to achieve. He was excited to know that I was based at Ballarat.He planned to fly over and see me. I had a dental appointment today and was told the news of his death by my dentist. It was a very gloomy couple of fillings. No funeral date as his body is being held in South Australia while investigation is underway. short news report in link. http://www.abc.net.au/news/video/2010/05/02/2888254.htm?site=centralvic&section=video

[troed@aon.at]

Well in Europe we have the rigid rules of Section-T, adopted from GB, although I sumtimes wonder how SOME serial gyro-types passed THAT. They have flaws not by HTL/CTL-issue but basic problems like welding etc.

Then we have the individual certs-procedures in each country insisting on stupid issues like Transponder, ELT etc.

And then we have the manufacturers that suffer from all different regs. But all in all the basic design origins from the Jukka Tervamaki and Vittorio Magni designs that proved to be safe.

So at least in THIS corner of the world we drown in regulations but at least and finally : WE FLY ..................

[PTKay]

Like i said....if someone says 'this is safe' then the lawyers will come after you when something bad happens!

I think, you don't get it.

Nobody is going to tell you, that certain gyros are absolutely safe,
and give you a certificate for it This is not going to be a certified a/c.

They are going to ban you from using something, that is WELL KNOWN
to be inherently unsafe and can kill you in a second by a slightest mistake.

Are you going to suggest, that drunken people should be allowed to drive cars?

If you ask them, most of them will tell you, they can drive perfectly safe
after a few drinks.
But it has been scientifically and empirically proven, that they are not.

And this is the reason to ban them form driving.

It has been scientifically and empirically proven, that HTL gyros will PPO.

And for me this is the reason good enough to ban them.

The freedom of an individual ends, when the freedom and life of another individual is in danger.

By allowing unstable gyros we give some individuals the freedom to kill themselves,
but in that process we endanger other innocent people's lives, and their freedom to fly...

Growing number of HTL gyros accidents may result in a ban of all gyros, as stated above.

[Heron]

A unicycle with a faulty pedal will drop the operator quicker and he will ride it if he wants after been warned about the problem.
Some bruises expected.
If you know your gyro will bunt for bad design, it is your choice to fly it if the rules allow for this option.
Some death expected . . .
Why don´t everybody land dowind? there are no rules against it . . .
Heron

[PTKay]

So at least in THIS corner of the world we drown in regulations but at least and finally : WE FLY ..................

Yes, and we fly safe!

Not only the constructions based on JT/Magni ideas, but such original
constructions like Xenon have excellent safety record.

And the regulations obviously didn't kill the sport, just made it more safe and popular.

[bpearson]

PTKay

Show me the third party fatalities from recreational aircraft falling from the sky. Yet you are allowed to construct a trailer to transport your gyro with no inspections and then drive past pedestrians. A young boy was killed here last year when a faulty car trailer broke apart!

I think the USA sport aircraft is about right where things such as prop security are checked.....to protect the third party.

These are supposed to be experimental. If we didn't allow experimentation we would never have hit on CLT.

Don't expect you to agree so lets call it a day.

[Phenix5]

Has anyone noticed that Juan de la Cierva, inventor of the autogyro, designed all his aircraft WITH an HS back in the 20s? I wonder why?????

BTW, did you know that the very first fatal accident on a De La Cierva's design happened thirteen years after the first succesful flights? And it happened because the pilot failed to remember releasing the securing blocks from the rotorhead that were used to prevent wind flapping on the ground. How about that for a safety record!

I don't think there is any other flying machine that can hold that safety record, specially on a newly developed aircraft as the autogyro was in those days and with the limited technology available by then.

Today, with all our computer assisted designing, high tech materials and proven statistics, how is it possible that still there are people/designers who build/sell autogyros without a HS.

When talking about gyros, just the mention of the word "unstable" inmediately the next word in your mind is danger! Is that so difficult to learn?

Honestly I think we should pay more attention to the father's teaching than to an inheritance from the fifties...

[All_In]

Has anyone noticed that Juan de la Cierva, inventor of the autogyro, designed all his aircraft WITH an HS back in the 20s? I wonder why?????
...

I thought it was because he realized that even GOD could not make a bird fly without one? :lol: :boink:

[barnstorm2]

. If we didn't allow experimentation we would never have hit on CLT.

.

Cierva patented Centerline Thrust for gyroplanes 75 years ago (UK patent #330513).

http://www.rotaryforum.com/forum/attachment.php?attachmentid=17943&d=1136600902

[bpearson]

In small recreational pusher gyros barnstorm! Obviously CLT is not new....but it took the freedom to tinker to come up with a Dom.

[barnstorm2]

In small recreational pusher gyros barnstorm! Obviously CLT is not new....but it took the freedom to tinker to come up with a Dom.

no.

Bensen was well aware of the requirement that propeller thrust act through the CG and that was reflected throughout his literature.

Of course, Cierva beat him to it by 30 years with his 1930 patent of CLT.

The scan below is from a 1966 edition of the Bensen flight manual which clearly shows propeller thrust in line with CG.

If only the people “improving” with Experimental designs.. mod-ing the Bensen design had read…

http://www.rotaryforum.com/forum/attachment.php?attachmentid=30090&d=1170001811

[Mark E]

....................

To say gyro operation in Australia are over regulated is ludicrous. At present gyro's are controlled by a non government body of gyro enthusiasts that allows anyone to build a gyro and fly it basically anywhere he or she likes with few rules.

We wouldn't register a gyro that used plastic bolts so why would you register one with a 12 inch offset in the thrustline?. ...................


Murray makes an excellent point here - certain major structural faults now would preclude registration of a gyro:

1. ...so why not simply include a weight/balance/thrustline test requirement in the process?

2. In 'fairness' to those who have already plonked their cash down on an HTL machine, don't make it retrospective (but THESE are the guys you'd have to focus on with an education plan)

3. In further 'fairness' for those who are building, also provide a 6 month phase in period.

If it saves lives, and also prevents the involvement of a government body in the process, it is certainly worth doing.

No-one could logically argue it was a bad thing - you can't deny the laws of physics, and mathematical calculations.

[bpearson]

no.

Bensen was well aware of the requirement that propeller thrust act through the CG and that was reflected throughout his literature.

Of course, Cierva beat him to it by 30 years with his 1930 patent of CLT.

The scan below is from a 1966 edition of the Bensen flight manual which clearly shows propeller thrust in line with CG.

If only the people “improving” with Experimental designs.. mod-ing the Bensen design had read…

http://www.rotaryforum.com/forum/attachment.php?attachmentid=30090&d=1170001811

So, should we be able to experiment or not then?

[Mark E]

So, should we be able to experiment or not then?

It would seem sensible to allow experimentation with everything except the basic physics of the process of the thing flying .... (and of course known facts about structural integrity)

For instance, no fixed wing designer would ignore the weight and balance of his plane. If he gets it wrong, he could probably still make it fly, and train himself to make the required responses... but if he eventually crashed he'd certainly be called to account for this known error.

Perhaps the problem with a similar situation in a gyro is that nothing too untoward happens until you reach the edge of the flight envelope, and then it happens suddenly, and counter to normal reflex reactions?

(then, it's a single seat fatality, recreational/experimental craft, dearth of official knowledge; ....etc, etc).


Perhaps it is sensible to self regulate where, and while we still can.

[barnstorm2]

So, should we be able to experiment or not then?

Oh, don't get me wrong.

I am a libertarian. I despise rules and regs and I very much enjoy the right to design and build experimental aircraft.

The point for me is that this issue is about a FLAW.

We have a situation where this is a KNOWN flaw but people are (were) selling mass produced kits or plans that suffered from this flaw. **

Even though the flaw is now very well known customers of these companies or purchasers of used machines are dying from the effects of this flaw.

We can take some action to make sure new pilots/owners are aware of this LIFE THREATING situation OR we can let it cause our entire sport to be banned.

What seems better?






** one vendor is still selling these and claiming to be the "industry leading aircraft", "The Gold Standard in Gyroplane Safety" "_______design improves the controllability and acceptable flight characteristics of the gyroplane"

With blatent lies like this from the vendor(s) how can our hobby hope to 'self regulate'?

If you tell me you are selling me a bomb and I buy it, I am ok with that.

If you tell me you are selling me a teddy bear but it is a bomb and I buy it, I am NOT ok with that.

.
.

[PTKay]

So, should we be able to experiment or not then?

Keep experimenting.

If your mum told you: "This iron is hot, don't touch it."
you probably kept "experimenting" and got burned.

I was sure you grew up since then.
But if you wish, keep experimenting.

If somebody before touched this iron and burned himself,
and tells you, it is hot, of course it's your choice
and "freedom" to try it yourself again.

But it has nothing to do with the progress you claim is created
by "experimenting".

The progress comes from learning from earler experiments,
absorbing this experience and not repeating the mistakes.

So now, you can jump into a 12 in. HTL, overpowered gyro,
and show us your guts.

Keep on experimenting.

[C. Beaty]

Here is Cierva’s 1929 British CLT patent application. After 80 years, people are still arguing about it and coming up with trick ways of beating the laws of physics.

[bpearson]

Keep experimenting.

If your mum told you: "This iron is hot, don't touch it."
you probably kept "experimenting" and got burned.

I was sure you grew up since then.
But if you wish, keep experimenting.

If somebody before touched this iron and burned himself,
and tells you, it is hot, of course it's your choice
and "freedom" to try it yourself again.

But it has nothing to do with the progress you claim is created
by "experimenting".

The progress comes from learning from earler experiments,
absorbing this experience and not repeating the mistakes.

So now, you can jump into a 12 in. HTL, overpowered gyro,
and show us your guts.

Keep on experimenting.

I wouldn't fly that thing for all the tea in China. Nor would I do heroin, go over the falls in a barrel or base jump....but I don't feel any need to stop others!

[GrantR]

If people keep building unstable gyros and making smoking holes well there probably will be more regulations to come. A safe range for Thrust line placement and a way to calculate its position while designing should be considered in any gyro design like weight and balance is considered in airplane design. You don't see people building tail heavy airplanes and calling them safe to fly.

I don't understand why people continue to build gyros with the seat a foot off the ground and the Thrust line aligned with the back of their heads!

If its for looks or ground handling that ludicrous! Maybe they do it because it is just a tad easier to build vs doing a drop keel mod however If you want a simple bensen frame with a big prop raise the freaking seat up so the prop is not aligned with your head.

In the drawing the seat on the CLT is only 3.5 feet off the ground and 2.5 higher than the HTL. A small change for a big improvement. This is with a 72" prop

[RotoPlane]

I haven't seen this, but what is needed is a spreadsheet that will give a CG to thrust-line value, after inputing the thrust-line location and some weights and their location. Free down-load for anyone. I had decided to make one at a point in my build....if I couldn't find one. It must be simple and easy to understand. I really don't think that people flying an HTL gyro can tell you what offset they have.....and would be shocked if the spreadsheet said it fell outside reasonal limits.

[PW_Plack]

...what is needed is a spreadsheet that will give a CG to thrust-line value, after inputing the thrust-line location and some weights and their location...

If someone hasn't reached the point at which he can do this himself, or even do the math without the spreadsheet, he's probably not qualified to be designing aircraft for others.

If I was wheeled in for surgery and the doctor had a big color chart of the human body labeled with arrows, I'd be just as nervous.

[Murray Barker]

Here is an Australian gyro with a Rotax 912. Even with the gearbox up its not hard to get the cog/thrustline right.

The seat is still an easy to get into distance off the ground.

[Fl90]

O.K.

in that picture:

55% of the person is below the line
85% of the airframe is below the line
100% of the fuel (1/2 tank fill) is below the line
100% of the motor is belw the line

so, the rotor weighs about 150lbs.

I could hedge an orange grove with a rotor like that.

[RotoPlane]

If someone hasn't reached the point at which he can do this himself, or even do the math without the spreadsheet, he's probably not qualified to be designing aircraft for others.

If I was wheeled in for surgery and the doctor had a big color chart of the human body labeled with arrows, I'd be just as nervous.

I wasn't talking about a gyro company. I was referring to individuals who buy a gyro from someone else. How many buyers do a hang test before they buy, or even after the sale? I would say very few. If there were an easy way for them to do it without a lot researching, perhaps more gyro pilots would make an attempt to find out if their machine was within acceptable safe bounds. Maybe not……

[Vance]

I wasn't talking about a gyro company. I was referring to individuals who buy a gyro from someone else. How many buyers do a hang test before they buy, or even after the sale? I would say very few. If there were an easy way for them to do it without a lot researching, perhaps more gyro pilots would make an attempt to find out if their machine was within acceptable safe bounds. Maybe not……

One of the papers that are supposed to be carried in the aircraft for those under the authority of the FAA is weight and balance. I cannot imagine how you would fill out weight and balance without doing a hang test. Mine is in degrees and clearly states the datum line and the location for the primary variable loads.

One of the things I was asked to do in my practical test for my private pilot’s test was to do weight and balance with a particular passenger load and a particular fuel load.

This is not related to thrust line compared to the vertical CG that in my opinion is the point of this disagreement.

This is one more good reason to get competent instruction.

In my opinion the location of the vertical and horizontal center of gravity has a lot to do with how a gyroplane flies.

Thank you, Vance

[RotoPlane]

Vance - In my opinion the location of the vertical and horizontal center of gravity has a lot to do with how a gyroplane flies.

And I fully agree....but vertical CG verses thrust-line is not covered by weight and balance. And some do not know why this CG to thrust-line distance is important or why a HS should be mandatory for that matter. The only point I was trying to make was to make it graphically easier for those few to understand these pitfalls. The status quo is unacceptable.

[birdy]

I wasn't comparing any of those to a gyro.....I was comparing the rush to regulate gyros compared to other pastimes.
certainly sounded like it to me.

I don't know the legal system in Australia but you should be very wary of amateurs starting to issue regulations.
Couldnt agree more.
But noones askn ingnorants to make the ruels.
Muz is sayn that ASRA, our non gov body do the regulaten, not sum brain dead public servant from CASA, who'd know jacsh1t bout gyros, but thinks he dose.

I am a libertarian. I despise rules and regs and I very much enjoy the right to design and build experimental aircraft.
Theres a limit to everythn.
I hate be'n told wot to do by sumone who wouldnt know jacsh1t too, but i have no problem with the cops taken them selfish f^%$wit drunks off the road.

We can take some action to make sure new pilots/owners are aware of this LIFE THREATING situation OR we can let it cause our entire sport to be banned.

What seems better?
So, your sayn that the blokes who'v been getn away with it for a few years shouldnt be saved/ educated.
I flew for 5 years before i knew anythn bout PPO, sure glad i know bout it now.
Ignorance is bliss, but only till it bites your ass.

[barnstorm2]

but i have no problem with the cops taken them selfish f^%$wit drunks off the road.

We can take some action to make sure new pilots/owners are aware of this LIFE THREATING situation OR we can let it cause our entire sport to be banned.

What seems better?
So, your sayn that the blokes who'v been getn away with it for a few years shouldnt be saved/ educated.
I flew for 5 years before i knew anythn bout PPO, sure glad i know bout it now.
Ignorance is bliss, but only till it bites your ass.

Agreed.

It does seem unfair to implement a system (or try to) that saves the lives of people purchasing a new gyro and not those already flying.

I thought about this for a few minutes.

Perhaps the fact that a current owner of a highly unstable gyro will have an issue reselling his machine will wake a few people up?

No easy answer from me but at least the new comers will have a good shot of not PPOing. Plenty of high timers have PPO'ed but the low timers are at highest risk.

.

.

[Heron]

Usually people that don´t like rules are the ones that complain the most when some rule is broken and he/she is on the loosing side . . .
I don´t see them jumping of a cliff . . . (well, some do)
If the Top Authority will cut all action and ban the entire section, then those in it are the most interested in monitoring, enforcing and creating new rules so that section can survive.
After experimentation comes regulation to sell, that is where the "thing" hits the fan!
At fly-ins the organization should have inspections and limitations to fly.
You get your card, schedule and all the protection you need to fly safer, even if you are experimenting your ship.
Heron

[Semler]

Hi all,

Just to clear some things as i know some people that have examined this thread are rather pissed off, They have asked me to clarify some of the unfounded remarks.

The gyroplane in question did have a H/Stab installed, with a Down loading pressure applied. The stab area is .3sq mtrs positioned 1.8 mtrs from the CG point.

Also the thrustline of this Gyroplane is not 12 inches! you must remember that there is alot of engine above the thrustline and simply looking at a picture does not do it justice.

Some tests this week on the same design of gyroplane has came to within the range of CLT +/- 2 inches of the CG. this is also what was accomplished with a sistership gyroplane (G110) that was tested at the 2007 Gyroplane Nationals At Lameroo, Which i believe was tested by some contributors of this thread.

The evidence also shows prior to the Bunt over the engine was not operating in the air, as only 2 of the 3 propeller blade were detached with the one still attached to the propeller hub and in the vertical down position with no visible rotorblade impacting marks.

Also included are some pictures of the H/Stab And a picture showing the Downloading force applied.

Regards,
Trent

[HobbyCAD]

So, ....what's the verdict?

Is G102 a CLT, not the deathtrap it is made out to have been, or an HTL, the deathtrap it is being "opinionated" to have been?

A lot of "expert" statements were flung around, I'd like to know which of the "expert" opinions were in fact, correct?

[RossB]

You may need to check the area of the horizontal stab. It looks smaller than 0.5 sq meters.

Ross B

[Semler]

Hi Ross,

I just got it rechecked and yes your right it should be 0.3 sq meters

[birdy]

The gyroplane in question did have a H/Stab installed, with a Down loading pressure applied. The stab area is .3sq mtrs positioned 1.8 mtrs from the CG point.

Also the thrustline of this Gyroplane is not 12 inches! you must remember that there is alot of engine above the thrustline and simply looking at a picture does not do it justice.

All points taken, but with all due respect for this bloke, it dont change the need for sumthn to be dun bout educaten the ignorant bout the effects of bad instability.
If sumone with more balls n brains insists driven a bad machine, good luck.
But for those who dont know the effects, we'd have trouble sleepn if we just let ' market forces' take its corse.
There aint alot of gyros round ere, and every tom, dic n harry for a 1000 miles knows im the nut thats been flyn um for a while. Im glad that most of um at least ring me before they purchase, and i insist i hava look and test fly it first wen they get their first machine. [ no matter who made it]
Makes for good sleeps.

Theres a couple of blokes ere that iv never talked to, and the only time they are flyn is just before they trash it, agin. :(

[Vance]

Hi all,

Just to clear some things as i know some people that have examined this thread are rather pissed off, They have asked me to clarify some of the unfounded remarks.

The gyroplane in question did have a H/Stab installed, with a Down loading pressure applied. The stab area is .3sq mtrs positioned 1.8 mtrs from the CG point.

Also the thrustline of this Gyroplane is not 12 inches! you must remember that there is alot of engine above the thrustline and simply looking at a picture does not do it justice.

Some tests this week on the same design of gyroplane has came to within the range of CLT +/- 2 inches of the CG. this is also what was accomplished with a sistership gyroplane (G110) that was tested at the 2007 Gyroplane Nationals At Lameroo, Which i believe was tested by some contributors of this thread.

The evidence also shows prior to the Bunt over the engine was not operating in the air, as only 2 of the 3 propeller blade were detached with the one still attached to the propeller hub and in the vertical down position with no visible rotorblade impacting marks.

Also included are some pictures of the H/Stab And a picture showing the Downloading force applied.

Regards,
Trent

Hello Trent, why do you think he crashed.

Thank you, Vance

[Semler]

Hi Vance,

I believe like so many crashes we may never know exactly what has happened, I dont like to come to a conclusion without 100% of the facts and only believe in presenting the facts we do know at this point in time. Speculating can sometimes do more harm than good.

Regards Trent.

[bosca]

Semler,The facts,it depends on your definition.If you were not present then it may become a hypothetical.Listened to Geffory Robertson lately?
Kym.

[Jazzenjohn]

<Also the thrustline of this Gyroplane is not 12 inches! you must remember that there is alot of engine above the thrustline and simply looking at a picture does not do it justice.>

The engine weighs about 160 pounds and the center of its mass is only a few inches above the thrust line, at best 6 inches, so it would have a moment of 80 foot pounds above the thrust line.

A pilot weighing 200 and seated about 18 inches to 2 feet below the thrust line has a moment of 300-400 foot pounds below the thrust line. That alone far offsets the engine.

The pod, gear, fuel, tail and keel are also well below the thrust line. The only signifigant mass above the thrust line is the rotorhead and blades.

I don't think the thrustline offset is 12", but it isn't plus or minus 2".

Also, the pod seems rather large in comparison to the tail area. I'm not sure how well it would handle in a crosswind. That could have been a factor too.

I think it's completely unacceptable to simply say "I believe like so many crashes we may never know exactly what has happened" and pass off examination. There isn't going to be any legitimate examination of the causes other than what we ourselves do. It may not be perfect, but it all we have.

[Murray Barker]

Trent, firstly the gyro has bunted over. I have seen enough buntover accidents to see the pattern here. I have had the unfortunate pleasure of attending numerous.

There has to be a force acting above the COG for this to happen and your comment that the engine was "not operating in the air" is incorrect.

Secondly the fact that only two blades were taken of by the rotor blades means nothing. I have seen buntover accidents that only took the tips off two blades..

Thirdly a piece of flat plywood .3 SQM isn't a horizontal stabilizer.

Lastly your friends may be even more pi**ed off when the rules are changed,but I hope they are pi**ed off until they are very old and gray.....

[Semler]

I agree completely that its bunted over,

Tell me would a gyroplane with no thrust ie engine stopped, and made to unload the rotors, bunt or look like a bunt? and then would that also mean that it wouldnt matter if it was CLT HTL or LTL ???

If you applied the same with an engine going and made it unload would it make a difference if it was CLT HTL or LTL ?


The vertical CG preformed during the week came out two 2 inches blow the thrustline.

Also John Downings G110 Gyroplane was done at the 2007 nationals which is identical to this machine came out the same and he remembers being told that it was so close that there's nothing it it and was CLT im taking that as in the +0 to 2 inch range. I believe that you may have even been there.

Also this im very interested in, Would a H/Stab as pictured with the download that it has (which i do not know how many degrees) with the moment arm that it has still play an important part? even if it is only .3sq mtrs.

So somehow im sure the designers of this type of frame wont be pissed off as they meet the CLT Range. Probably only pissed off that people have beaten their drums and instead of talking to designers before hand.

Cheers

Regards Trent

[Heron]

Opinions are not supposed to be correct when offered, they will be proven rigth or wrong as the discussion progresses.
If you can go step by step, step aside and wait until the end of the investigation, pick your line of thinking and be happy with whatever conclusion that will suit your needs.
The experts will help the authorities to create and enforce rules that will give more chances for the students to stay alive during the learning curve and thus make aviation safer.
Heron

[Greg Mitchell]

Trent, firstly the gyro has bunted over. I have seen enough buntover accidents to see the pattern here. I have had the unfortunate pleasure of attending numerous.

There has to be a force acting above the COG for this to happen and your comment that the engine was "not operating in the air" is incorrect.

Secondly the fact that only two blades were taken of by the rotor blades means nothing. I have seen buntover accidents that only took the tips off two blades..

Thirdly a piece of flat plywood .3 SQM isn't a horizontal stabilizer.

Lastly your friends may be even more pi**ed off when the rules are changed,but I hope they are pi**ed off until they are very old and gray.....

Trent and HobbyCad,

I object to the wording of early report suggesting pilot error. A claim made by early onsite ASRA investigator/s. To make such a claim so early in an investigation I thought ill-founded.

I re-iterate my belief that there are some TA's, Instructors and builders, who are still claiming substantive benefits of HTL gyros over the near CLT designs.

I believe Murray would not make the above claim as to cause without said evidence to support same. This seems to be at odds with the claim the pilot made an error. My understanding is PPO is the result of a design fault.

People manufacturing parts for HTL gyros can just as easily do so for near CLT gyros.

My gyro's HS is in-line with the thrust line, no load and is approx .8 sqm and 1.6 m behind the vertical C of G. Thrust is slighly below the vertical C of G.
My gyro will not PPO.


So, ....what's the verdict?

Is G102 a CLT, not the deathtrap it is made out to have been, or an HTL, the deathtrap it is being "opinionated" to have been?

A lot of "expert" statements were flung around, I'd like to know which of the "expert" opinions were in fact, correct?

No it is not CLT. Far from it. It is a HTL gyroplane.
I believe it is/was an accident waiting to happen. That may be opiniated.
I'm no an expert. I believe I understand the facts.

Fact is we have had to many deaths caused by HTL gyros PPOing......why not look again at what may be done to stop this from happening, when we know the physics and aeronautical principles involved.

I believe, as Chuck commented on Murrays post and as I inferred previously,

Originally Posted by Murray Barker
Hobbycad,There seems to be some sort of notion this is an isolated case.The predominent theme in single seat gyro accidents in this country is powerpushovers.

The same is true in the US although the chorus of hand wringers would have one believe it is entirely due to lack of training.

And in a sense it is because many CFIs are not educating their students about the danger of flying a rat trap.

Time to sort it out...gyros can be modified....in the right direction.

Trent, Hobbycad, I hope this addressess some of your questions.

The whole Investigator thing needs addressing. Who speaks to the press etc. Instrcutors and TA's need to be on the same page...CONSENSUS!

Lobbying for change does not have to mean there will be a wide spread and far reaching regulation.........MORE DEATHS WILL ENSURE IT.

[Semler]

I Agree PPO Is a problem but im not talking about POWER push over im talking if someone unloads a rotor what will it do? what will it look like?? has it ever been record as such or just written off as PIO leading to PPO?

I truely agree that CLT is a Great thing for Gyroplanes as it sorts the problem of PIO.

Investigators Said it might have been pilot error? Where there not also police investigators present? Was there also other people present that may have said something that the media picked up in passing? I've been to many Accident scenes (not gyro related) and know that the media are vultures and will even make unfounded reports to make the nights new that bit more interesting.
Have you asked the initial Investigator if they said such words???? Instead of sprouting off give him a ring im sure he would love to have some encouraging words thru this difficult time.

Cheers

Regards Trent.

[Greg Mitchell]

Sprouting off... Hmmm!

Sorry Trent I was giving my point of view as were you. Now I think the message has gone astray.

You apparently think I am singling out someone in particular.

I am distressed about the loss of life at this time and trying to suggest ways to reduce the numbers in future.

You your self suggested education.

I dont understand your need to be asking these questions.

I'm sorry if I have offended you, that was not my intent.

I will not be contributing any further to this thread.

[Semler]

Sorry Mitch perhaps the Word Sprouting off is over the top. I Apologize.

Please im here to learn as much as anyone else here, Please dont stop contributing to the thread.

I'm fustrated that the design is 2 inches above V-CG is labeled as unsafe.

Regards Trent

[C. Beaty]

Power off, propeller thrust line location vs. CG has no relevance; all gyros are the same from that perspective.

The pitching behavior when a rotor is unloaded then depends upon residual moments about the CG, the main force being airframe drag. Airframe drag should also be centered on the CG; fairly easy for high riders, impossible for low riders.

High riders present the illusion of having more undercarriage drag but the location of wheels is set by ground to propeller clearance considerations. Nearly all gyros will have wheels located to provide 6-12 inches of clearance.

Offsets of airframe drag can be fully compensated by horizontal tail surfaces; aerodynamic drag and lift follow the same law. If compensation is complete at 40 mph, it will also be complete at 100 mph.

[All_In]

Thank you Chuck that is what I needed to know.

[HobbyCAD]

Power off, propeller thrust line location vs. CG has no relevance; all gyros are the same from that perspective.

The pitching behavior when a rotor is unloaded then depends upon residual moments about the CG, the main force being airframe drag. Airframe drag should also be centered on the CG; fairly easy for high riders, impossible for low riders.

High riders present the illusion of having more undercarriage drag but the location of wheels is set by ground to propeller clearance considerations. Nearly all gyros will have wheels located to provide 6-12 inches of clearance.

Offsets of airframe drag can be fully compensated by horizontal tail surfaces; aerodynamic drag and lift follow the same law. If compensation is complete at 40 mph, it will also be complete at 100 mph.

Thank You Chuck, now this is the type of answer I was looking for. I can now use it to make up my mind about G-102.

Thanks for that.

[barnstorm2]

The gyroplane in question did have a H/Stab installed, with a Down loading pressure applied. The stab area is .3sq mtrs positioned 1.8 mtrs from the CG point.

Also included are some pictures of the H/Stab And a picture showing the Downloading force applied.



Trent,

As already stated the .3 HS appears to be mathematically insignificant for PPO avoidance.

Although the hstab appears somewhat raised it also appears to be out of the usable portion of the prop-wash and perhaps also in 'dirty air' from the airframe.

According to tests done here:

http://www.rotaryforum.com/forum/showthread.php?t=11671&highlight=prop+wash+immersed

and here:

http://www.rotaryforum.com/forum/showthread.php?t=16752&highlight=prop+wash+immersed

The propwash is a cylinder that's 1/2 - 2/3 of the diameter of the prop itself.

This outcome means that you cannot rely on a H-stab down at the level of the keel tube to counteract the effects of high thrustline. At low aircraft airspeeds, such a HS simply won't prevent a PPO in the event you get smacked by a strong downdraft while throttle is way up. The HS MUST be elevated at least a third of a prop radius up into the wash (more if possible) to catch some fast flow, if it's going to be a reliable PPO preventer.

http://www.rotaryforum.com/forum/attachment.php?attachmentid=69195&d=1273209322

.

[Jazzenjohn]

What blades did the accident gyro have on it? Were they the same or different blades than the Thrustline test in 2007?

[barnstorm2]

What blades did the accident gyro have on it? Were they the same or different blades than the Thrustline test in 2007?

That is a good question.

Was a double hang-test used for the determination?

looking at the redrive turned down, I very much like how the engine weight is arranged. Pity about the battery and pod. Where is the gas tank?

I could see how with a heavy set of blades the off-set could be reasonable.

From nothing more then eye-ballin it I can't help but wonder if the principle danger is a PPO-induced by by Drag-over?

I am having a hard time seeing that wee little hstab fighting against that pod and windshield.

.

.

[Semler]

Hi All,

Okay i think im starting to get my head around this.

So if the Thrustline is 2 inches from CG we must look else where.

Therefore we come to center of pressure. How do you work out the center of pressure? Is the only way to take a photo side on as if it was just about to go flying and then cutting around it carefully and then getting a pin and poking it into the cutout until you find its center point?

What way can we adjust for it if its below the CG? is it a matter lifting the pod or is there another way?

Thanks for your replies,

Regards Trent

[splashdown]

Doing the "cutout the side-on photo' will only give you a VERY BASIC indication of the front to back location of the centre of pressure.

There two other axis to consider. There is also the shape (smooth/rough/flat/rounded) of the airframe/pod/tail etc..

This photo method is pretty useless if you ask me.

[Semler]

I see your point about the shapes, How would you do it Splashdown? Is their a better way?

I did abit of research and have found that the Sparrowhawk suffered from runaway speeds if the power was reduced to idle and was left to go on it natural course is this also due to the centre of pressure differences from the vertical CG?

Cheers

Trent

[splashdown]

I'm not sure there is a good practical test you can achieve at home. A wind tunnel would be the best method of capturing all factors, however you still need to test more than just one angle.

By my simple understanding of all things physics, I would expect the centre of pressure to change dramatically as the airframe rolls forward into the relative airflow. Certainly a bathtub-like pod is going to catch a lot more air after it rolls forward through 90 degrees than it does in forward flight.

So in my opinion (there is that word again) COP will change depending on the relative airflow over the gyro and pilot.


As for your discussion on the Sparrowhawk - I'm not sure I understand the situation you are describing. Are you saying if you cut power and go hands-off, the SH will nose down and keep on accelerating?

[Semler]

Hi Lloyd

The Sparrowhawk sitiuation is in the thread link below Post 45, the whole thread is very interest but time consuming, doesn't help that im not a very good theoretical person and more of a show me kind of person.
I can tell ya one thing i know, This whole accident has opened my eyes up to gyroplane forces.

http://www.rotaryforum.com/forum/showthread.php?t=19957

Another question im hoping someone may help me out with is would the RTV rotor thrust vector also play a part in this COP/CLT situation? and if yes or no How/Why

Cheers

Regards Trent

[C. Beaty]

I’m not sure I understand the question but I’ll take a stab anyhow.

A rotorcraft with flap hinges on the center of rotation is controlled by “thrust vector orientation.” Meaning the pilot orients the rotor thrust vector about the CG in some desired direction to begin a pitch or roll acceleration.

It’s similar to a yo-yo rolling down a string; let go and the yo-yo goes ever faster. A yo-yo with most of its mass concentrated at the rim accelerates more slowly than one with most of its mass concentrated at its center. A high inertia yo-yo vs. a low inertia yo-yo.

A yo-yo with aerodynamic paddle blades would reach terminal velocity more quickly than one without. Terminal velocity is reached when aerodynamic drag equals the accelerating force of gravity: that would be the product of gravity acting on the yo-yo and the offset of the string from the center of rotation.

The paddle blades provide damping.

[gyrogreg]

Many of you will dismiss what I have to say, but here it is anyway:

- Pictures can't tell you if the HS is downloaded - just from its mounted Angle of Incidence on the frame. All of the pitch moments, including airframe drag and prop thrustline, will force the HS into whatever in-flight AOA is required to balance the Sum of Static pitch moments.

- There is much more to PPO (buntover) or PIO susceptibility than the simplistic static analysis. The Dynamic damping provided by a very effective HS is a big contributor - even on fairly HTL configurations. The HS on this gyro has been argued to be fairly ineffective. It was located far aft - VERY good for DYNAMIC damping. But, it was small and flat. Better to be large and aerodynamic shape.

- IMHO, typically, high seaters - chasing the illusive CLT - present a lot of lower end drag with the long landing gear. When the prop is not running, there is no such thing as CLT, LTL, or HTL! When the prop is not running on such a gyro, the airframe drag at high airspeed can easily position the RTV forward of the CG. A statically unstable condition.

- Longitudinal balance - weight and balance - has little to do with the real static issue of the CG - RTV relationship. ANY pitch moments on the airframe can sum up to the statically unstable condition with the RTV forward of the CG. On a HTL, this may be the case with power on, or off. For CLT or LTL, this is likely the case with power off at higher airspeeds (draggy things pulling the nose lower and the RTV forward of the CG!)

My point is that gyro seats don't have to be 3 feet above the ground to be stable! Total reliance on just the STATIC assessment of the CG - RTV locations, IMHO, is ignoring the potentially overpowering benefit of a good DYNAMIC damping HS. There is more to aeroDYNAMICS than STATICS.

There are many people around the world laughing at our American, and apparently Australian paranoial focus on HTL. HTL can be bad, unless you do it right. IMHO, "right" is with a good size and effective DYNAMIC damping HS. You can do "right" with just about any configuration - MAYBE. But, doing it "right" is not just raising the seat up 2 feet!

If you want to assess if HTL is neccessarily dangerous and prone to PPO or PIO, the best indicator would be actual accidents. If you want proof that HTL may not be all of the story - see if you can find any Magni gyro PPO or PIO accidents anywhere in the world! Can't find them! But, many will argue, and I won't argue with, the fact that Magni gyros have a significant HTL! That's my proof that high seats are not the whole story! Want to know the real reason that Xenons, Magnis, MTs, ELAs don't have buntovers or PIO incidents, whether CLT or HTL - they all have very powerful DYNAMIC damping HSs.

One thing I do agree with most of the posts on this thread - employ a good HS. To be a strongly effective DYNAMIC damper, the HS should be on a long tail - but it also needs to be more than just a token horizontal flat plate!

Thanks, Greg Gremminger

[RotoPlane]

You've presented a very good view point Greg, on the most important safety item at our disposal, the use of an "effective" high moment-arm HS. I would say the second important safety item is CLT. When we find ourselves at less than one G, with no forward speed (perhaps even a tail wind) and go to full throttle, the HS will not be as effective as normal, so flying a HTL gyro is not what I want at that moment. The third item on my list is a dampened rotor (like, over-balanced blades). Much can be done to a gyro to make it our safest flying machine.

[All_In]

Thanks Chuck, Greg, and Ed! I think I finally really understand! Ed you put the last piece of the puzzle together for me with a great example.

[SamL]

Hi Greg
I'm sure you agree, a CLT machine (disregarding its C of Drag above or below the CofG) will not pitch nose up or down regardless of power setting.
This is not the case for a HTL machine, as it all depends on the way the machine applies force to the HS.
If the HS is outside the prop wash the machine will rely on forward speed, to overcome the HTL issue. This is not ideal. If the HS is mounted in the prop wash any sudden burst of power will cause the HS to compensate instantaneously. The cost for such a design is reduced efficiency due to an increase of drag. This effects, fuel economy, speed, and climb performance. In my opinion it is a band aid for a poorly designed machine.
During an engine failure yes the CLT, HTL, LTL, argument goes out the window, but to say a high rider machines legs could cause a nose down or RTV to move forward compared to a low rider is wrong.
As you know a machines CofG stays constant, regardless of design, and a Low rider gyro compared to a high rider usually has a greater amount of surface area below the CofG, so this design has a greater chance of producing a nose down or moving forward of the RTV in front of the machines CoG.

Trent, if a gyroplane had a set of floats attached to it,then its frontal CofP would most likely be below its CofG. This is due to the machine producing greater drag below the CofG.
So in this example the machine,given it was a true CLT would still react just like a HTL machine lowering its nose and causing its TRV to also move forward of its CofG. This is why I personally wouldn't fit floats to my machine.
Idealy such a machine would require to be designed as a LTL machine fitted with a large HS.

Regards SamL...............

[Jazzenjohn]

<If you want to assess if HTL is neccessarily dangerous and prone to PPO or PIO, the best indicator would be actual accidents. If you want proof that HTL may not be all of the story - see if you can find any Magni gyro PPO or PIO accidents anywhere in the world!>

I'll bet there would be some if they had a .3 sq. meter flat plate stab on them. I'll also bet that there would be less accidents with a CLT Magni with a .3 sq. meter stab than a HTL Magni with a .3 sq. Meter stab. I'd be willing to bet that nearly every buntover that has ever happened was a HTL gyro. I'm also willing to agree that a well designed gyro with some amount of thrustline offset can be made safely. I agree that Magni gyros have an enviable safety record. None of this conjecture does much to solve the riddle of this particular accident. Both the thrustline as well as the inadequate stab have been pointed out in the accident discussion. The issue of COP is also rightfully brought up, and the fact it is often overlooked.

To me, there are several issues that need to be determined.

1, Was the engine on or off? If it is determined the engine was on, what approximate amount of thrust was there. If there was no thrust, engine TL is of little significance and COP needs to be looked at. Perhaps we can make some guesstimation how much effective horizontal stab is necessary for a gyro with a low COP.

2, If the engine was running and the craft bunted, what was the thrustline to COG? Is the thrustline to COG a bigger issue than COP? What amount of stab might be necessary to compensate for both a HTL as well as a low COP?

3, Are we accurately measuring thrustline offset? It is claimed it was within 2". It doesn't appear that way to me and some other people. It is also a variable. Changing fuel load, and pilot weight would effect it. Also changing rotorblades can have a big effect. If the 2007 test was with a light pilot and heavy blades and the accident craft had a heavy pilot and light blades it could easily lower the COG by several inches.

[gyrogreg]

You've presented a very good view point Greg, on the most important safety item at our disposal, the use of an "effective" high moment-arm HS. I would say the second important safety item is CLT. When we find ourselves at less than one G, with no forward speed (perhaps even a tail wind) and go to full throttle, the HS will not be as effective as normal, so flying a HTL gyro is not what I want at that moment. The third item on my list is a dampened rotor (like, over-balanced blades). Much can be done to a gyro to make it our safest flying machine.

I can dream up so many situations that we should be teaching gyro piltos not to do. Going to full power over the top of a zoom seems to be one that (I hope) everyone knows not to do in a gyro. Most instructors teach reducing power as the safe measure - but on a very LTL (without a good HS), that can also initiate a sudden nose down pitch movement - not a good thing to do if the rotor is unloaded. Any pilot that adds sudden power at the top of a low - G zoom, has not received good instruction!

In fact, the reducing power adage when in risk of unloading the rotor works BEST for HTL - where it pitches the airframe nose-up and loads the rotor. Reducing power at the top of a zoom in a LTL that causes the barely loaded rotor to go completely unloaded with a suden nose-down pitch, just isn't a good thing to do.

Still, I turn to the experience. There are well over 550 Magni gyros flying around the world - probably over the last 15 years! And, most Magni pilots fly around 200 hours a year. And, everyone of these go through hours oflow time novice timewhere they might be more prone to making such mistakes. Still, not a single report of PIO or buntover (PPO). So, I would certainly rely on high time expereince as the final arbiter of what works and what doesn't work.

It doesn't bother anyone if you want your gyro to sit on stilts. But, be sure you include an effective DYNAMIC damping HS. Without that HS, there is NO dynamic damping on the airframe - only what the rotor can provide, which may not be much on lighter machines. What you ultimately want is an airframe that follows the flight path dictated by the rotor. If the airframe does not have good dynamic damping, its pitch attitude may not indicate accurately what the rotor is actually doing - this can get pilots in trouble when you think the aricraft is doing something the rotor is not doingt - and then you try to correct it!!!

I'm just saying, and agreeing, that a good HS - on a long arm for good DYNAMIC damping - is the key to flight stability and safety - probably no matter where the prop thrustline is.

So, shoot for CLT if you must. You will probably never achieve that perfecftion. You need more than pure dependence on CLT! And that something more (HS), can correct for an awful lot of HTL - AND LTL!

Thanks, Greg

[gyrogreg]

Hi Greg
I'm sure you agree, a CLT machine (Regards SamL...............

Sam, I can agree with some of what you are saying, and not agree with others. But, I'm saying your analysis is thinking purely Statically - which completely dismisses the DYNAMICS!

The Magni indicates all the STATIC characteristics you mention - trimmed airspeed change with power change - all indicating a true HTL! However, all flight testing, done even by professional flight Test Pilots in the UK, indicate it is still statically AOA and Airspeed stable under all flight conditions of power and airspeed. This means it is incapable of bunting over in these conditions. The key the professionals look at most is DYNAMIC stability and damping. If an aircraft exhibits diminishing Phugoid oscillations - DYNAMICAL stable - it is then proven to be STATICALLY AOA stable - under those flight conditions - can't have Phugoid pitch oscillations without an effective static restoring pitch moment.

Yet, I would agree that these same machines are probally flying with the real RTV forward of the CG!!! Oh, blasphomy! You then infer that it should be able to PPO!!! But they don't, and the Dynamic Stability indicates the "effective" RTV is not forward of the CG - A static restoring pitch moment still exists. So, from this data, and from accident history (or non-accident history), there must be more than just the static analysis. I know it is hard, but accept that the STATIC threories so many have now - thankfully - begun to understand, are not the final word. The the next, if not final word may be DYNAMIC damping!! Until we factor in that important parameter, we are stuck in the limiting paradigm that only CLT will do! And, even CLT can PIO or buntover under the proper conditions - if it does not have a good HS. That is called "misplaced confidences". And, if that is forced into the rules by our new know-better-than you socialistic societies, gyroplanes will continue to be the left-behinds in aviation! The UK is now even starting to recognize that their 2 inch rule is lacking something - note thay have approved the Magni M16 for Section T, because their flight testing verifies the nearly 6 inch HTL still well meets their stability criteria - which is very stringent. Oh My!! Could Dr. Houston be wrong!!!

- Thanks, Greg

[C. Beaty]

Don’t you find it interesting, Greg, that the Magni lookalikes, ELA and MTO3, not having the magic Magni rotor, found it necessary to step the keel and go toward CLT even though the horizontal tails look the same?

I doubt that ELA stepped the keel for cosmetic reasons.

[RotoPlane]

Pilots can find themselves in dangerous situations whether trained well or not, by misfortune or fool-heartedness. A well designed aircraft (that is one that was designed to be forgiving of pilot error) will save lives.

The only disagreement I have with your statement above Greg, (boy, you can type well) is the importance of CLT for both weight and drag. I'm talking close to or an average of say +/- 3" max around CLT. An effective HS will make up for most of the difference from true CLT. The rest of the difference can be covered by a dynamic dampened rotor. I think one reason for the Magni good safety record (with the possible HTL) is due to what appears to be a dampened rotor.

But all in all I agree with your statements ;).

[bosca]

Thankyou Greg for your artical.You are very intellegent man who is not political and never puts down others,instead you seem to bring out the best is people.Maybe thats the respect that you command.
Kym Caskey.

[SamL]

Sam, I can agree with some of what you are saying, and not agree with others. But, I'm saying your analysis is thinking purely Statically - which completely dismisses the DYNAMICS!

The Magni indicates all the STATIC characteristics you mention - trimmed airspeed change with power change - all indicating a true HTL! However, all flight testing, done even by professional flight Test Pilots in the UK, indicate it is still statically AOA and Airspeed stable under all flight conditions of power and airspeed. This means it is incapable of bunting over in these conditions. The key the professionals look at most is DYNAMIC stability and damping. If an aircraft exhibits diminishing Phugoid oscillations - DYNAMICAL stable - it is then proven to be STATICALLY AOA stable - under those flight conditions - can't have Phugoid pitch oscillations without an effective static restoring pitch moment.

Yet, I would agree that these same machines are probally flying with the real RTV forward of the CG!!! Oh, blasphomy! You then infer that it should be able to PPO!!! But they don't, and the Dynamic Stability indicates the "effective" RTV is not forward of the CG - A static restoring pitch moment still exists. So, from this data, and from accident history (or non-accident history), there must be more than just the static analysis. I know it is hard, but accept that the STATIC threories so many have now - thankfully - begun to understand, are not the final word. The the next, if not final word may be DYNAMIC damping!! Until we factor in that important parameter, we are stuck in the limiting paradigm that only CLT will do! And, even CLT can PIO or buntover under the proper conditions - if it does not have a good HS. That is called "misplaced confidences". And, if that is forced into the rules by our new know-better-than you socialistic societies, gyroplanes will continue to be the left-behinds in aviation! The UK is now even starting to recognize that their 2 inch rule is lacking something - note thay have approved the Magni M16 for Section T, because their flight testing verifies the nearly 6 inch HTL still well meets their stability criteria - which is very stringent. Oh My!! Could Dr. Houston be wrong!!!

- Thanks, Greg

Greg
I never said the Magni is unstable and I did state its pitch stability is due to the band aid fix by effective use of its HS.
If pitch instability, or unstable in A0fA is caused by the rotation, lowering or raising of the machines nose which in turn moves the RTV, forward or aft of its CofG, then please explain to me how a true CLT (DISREGARDING ITS AERODYNAMIC CENTRE OF DRAG )machine can PIO/Bunt?
Remembering that a TRUE CLT machines forces all act though its CofG.

Regards SamL..............

[bosca]

Hang on Sam,I hope that you are not suggesting that a long moment arm and a good HS is a band aid fix to a fixed wing.
It's all about the total product in harmony
Kym.

[SamL]

Hang on Sam,I hope that you are not suggesting that a long moment arm and a good HS is a band aid fix to a fixed wing.
It's all about the total product in harmony
Kym.

Kym, were in my last post did I ever mention anything about FW
This is all about CofG, CofP, Thrustlines, HS's and the movement of a gyroplanes RTV.
Last time I looked, FW aircraft don't have an RTV :wacko:

[bosca]

Yes you did by inferance Sam.Suggesting that an effective HS is a bandaid fix.
Principals of flight.
Too much mathamatics has been quoted by statements.Leave that to the Magni and the butterfly designers/manufactures,for example.
Kym.

[birdy]

The only disagreement I have with your statement above Greg, (boy, you can type well) is the importance of CLT for both weight and drag.
Not to mention a HTL machines horrible power inefficiancy.

The one Magni i flew, i was supprised at how much performance it didnt have, for a 914 powered machine one up. :(

[birdy]

Kym, id call a big SH ona HTL machine a band aid, allbeit, an effective one.
Besides, a gyro can fly under 100% control without one.
Can a FW?

[C. Beaty]

You’ve never heard of a flying wing, Birdy? (but it is pretty tricky to get one to work)

[C. Beaty]

If an oxcart had automotive type steering, the ox could be hitched to the side of the cart. But why?

Aircraft can be made to fly with large offsets between CG and thrust line and in a few instances, such compromise is necessary.

Flying boats come to mind; one can’t have propeller tips dipping in the water. The penalty that must be paid is a large artificial load on the horizontal tail as well as some handling quirks.

Ordinary aircraft, Cessna for instance, nearly always have the propeller thrust line slightly below the CG even though the passengers must step up to board.

[bosca]

Bird,Are you suggesing to me that you fly without a HS with 100% control.Havent you moved on??Must be very confusing to those new to the sport to hear you make such a statement.
A Bloody dangerous illusion your creating Bird.
Kym.

[C. Beaty]

- IMHO, typically, high seaters - chasing the illusive CLT - present a lot of lower end drag with the long landing gear. Thanks, Greg GremmingerDon’t you suppose, Greg, that wheels are located in approximately the same relationship to propeller tips whether low rider or high rider and that you might have been fooled by an optical illusion?

Most gyros have 6-12 inches of propeller clearance with the wheels on the ground.

[SamL]

Yes you did by inferance Sam.Suggesting that an effective HS is a bandaid fix.
Principals of flight.
Too much mathamatics has been quoted by statements.Leave that to the Magni and the butterfly designers/manufactures,for example.
Kym.

Mate, A negatively loaded HS mounted to a HTL machine to counter the designs instability, in order to make it stable is in my book a definite Band Aid.

Why build an unstable machine, then spend much time and effort trying to make it stable, when you can simply just build it stable ???? and acheive all the added benifits?????

For those who cant comprehend such a simple statement then you may need more than what I am currently offering.

This is exactly what ASRA is currently investigating, and wanting to implement in Australia moving forward.......

Regards SamL...................

[gyrogreg]

Don’t you find it interesting, Greg, that the Magni lookalikes, ELA and MTO3, not having the magic Magni rotor, found it necessary to step the keel and go toward CLT even though the horizontal tails look the same?

I doubt that ELA stepped the keel for cosmetic reasons.

Hi Chuck,

I guess you are suggesting that the Magni rotor is the miracle device that makes Magni gyros so stable and accident free - even though HTL? I partially agree - the balance of rotor dynamic characteristics with the airframe dynamic characteristics probably do present a harmony that together help avoid PIO and rapid pitch changes that could initiate a buntover. I maintain that the dynamic characteristics of both the rotor and airframe, and of the combination of both, are what provides and maintains static AOA stability - an "effective" static restoring moment, even though the static sum of moments (and static testing) indicate the real RTV is likely forward of the CG.

If you are suggesting the large HS (airframe dynamic damper) does not play a large part of this, I must disagree - and I guess you and I will just have to agree to disagree on the full value and importance of the HS. I place much more value on the HS for more than just it's Static balancing properties.

It may be likely then, that flight testing the ELA (the MT is mostly a copy of the ELA) may have indicated a need for better prop thrustline alignement and some embedding of the HS. I doubt that though, I think they were likely just following the paradigm of the HTL mantra. But, even then, a general comment out of Europe is that the MTs and ELAs to not feel as solid and comfortable in turbulence. That may all be from the lighter and less damped rotor?

I did get a chance to fly the MT03 when Chris Kurze and Robert stopped by St. Louis in their cross-USA tour. I found the stick to be a bit less heavy (expected with the aluminum rotor), but it did "feel" like it had similar handling control responses to the Magni. I really wish now that I had performed a set of dynanmic stability flight tests - but the MT03 factory (and the British Section T testing) has confirmed that the MT03 meets the latest ASTM stability standards which would confirm the static AOA stability I would expect - if only from the dynamic damping provided by the big tail. If the tail were not so big, I would think the improved prop thrustline and embedded HS might be more necessary than I feel it really is now.

One reason I do think these "clones" have the raised tail is also to allow a slower, more tail low landing.

Thanks, Greg

[bosca]

Sam,where on earth did you get this idea that I support a HTL machine?My point has always been to argue of the importance of an effective HS and not these dangerous short coupled designs that are photographed in the ASRA magazine.
Show me the quote where you have come to this conclusion??
Hello Sam we have been flying gyros for decades,why this sudden flurry to fix when it should have been done years ago. Been lots of warning that many manufactures have heeded.
Kym.

[gyrogreg]

Sam,

I agree, that if you need to employ a lot of HS down-load to compensate for a lot of other nose-down moments, that adds to rotor load and inefficiencies.

However, if you do it all right, that compromise can be negligible - again as demonstrated by the Magni M16 - despite Birdy's claim that it is a dog! Let's see what other gyros can perform as well with 600 Lb useful load and 100 HP! Theoretically, the MTs and ELAs, with prop thrustline, should have better performance. I'm not sure that has ever been claimed or demonstrated. When we flew with Chris and Robert, they and some other Magnis were single seat, and I was with passenger near MGW in our M16, and we all stayed pretty well together:

One key component of "doing it right" is to minimize the total drag (and any nose-down moments) of the aiframe with clean airframe aerodynamics. For instance, wheel pants, airfoil shaped LG, aerodynamically slick (and by the way, Italian stylish) enclosure, etc. Clean airframe aerodynamics minimizes the balanceing job the HS has to do for the airframe aerodynamic moments.

Secondly, the longer the tail, the less extra load the tail download MOMENT will require on the rotor. That long tail also provides a square function improvement in DYNAMIC damping (Where the static balancing is only a straight function of the tail length!) Magni must have done some of this right, because the M16 manages to carry 600 useful load on 100 HP at at higher airspeeds than many of the 160 HP CLTs are able to do. The "secret" there (this is not really a "secret") is aerodynamically efficient airframe, HS - and rotor.

Thanks, Greg

[Aussie_Paul]

I truely agree that CLT is a Great thing for Gyroplanes as it sorts the problem of PIO.

Cheers

Regards Trent.

CLT sorts out the PPO problem, not PIO.

I can't believe 10 years after I started the CLT education process here in Oz that we still approve people to train in and sign off unstable gyroplanes. Worse that that, there are people almost making excuses for the system!!!!!!!!!!!

Aussie Paul. :)

[Semler]

Thanks Paul for picking that up for me :o

Well its fact that this gyroplane came out just on CLT, So as i see it the Centre of Pressure must be addressed, either by raising the pod or Creating a more effective H/Stab :drum:

Cheers

Regards Trent

If anything good has came out of it is that after discussing all this with my instructor i'll be rebuilding my current machine with the pictured style frame to address the VCG, thrustline and centre of pressure before i sell it.

:hippie:

[All_In]

@Greg
Is HTL designed into a Magni on purpose? My only other question currently is if you changed the Magni to CLT how would having it a true CLT effect it in all flight characteristics?

Would making a Magni CLT make it fly any differently = better or worst in any situation you can think of?

[gyrogreg]

Greg -------------- If pitch instability, or unstable in A0fA is caused by the rotation, lowering or raising of the machines nose which in turn moves the RTV, forward or aft of its CofG, then please explain to me how a true CLT (DISREGARDING ITS AERODYNAMIC CENTRE OF DRAG )machine can PIO/Bunt?
Remembering that a TRUE CLT machines forces all act though its CofG.

Regards SamL..............

Sam, I apologize, but IMHO, you are limiting your perceptions to just STATIC elements. IMHO, you can't just ignore the DYNAMICS part of aeroDYNAMICS.

CG, CLT, HTL, COD, and LTL are all purely STATIC elements. HS loads, and airframe loads, AND airframe airflow distortions of prop thrust, are all VARIABLE static elements that complicate these purely static elements also - these static moments can change significantly with static airframe pitch attitudes - very difficult to include in a purely static analysis.

But, I maintain the DYNAMIC properties provided by the airframe DYNAMIC damper, in combination with the DYNAMIC damping of the rotor, can offset or correct all the static variables that would be, in themselves, impossible to neutralize in all conditions anyway. When you are attempting to explain everything in Static elements, there are simply too many variables to achieve perfection.

I am not suggesting that consideration of the static moments is not an important element of a safe design, I'm only suggesting that everything is a compromise, and that there are DYNAMIC tools in the tool box that can be employed to expand the options. I am mostly just presenting the argument that it would be disappointingly limiting to the advancement of gyroplane safety, and to the sport, to put all your eggs in the CLT basket!

----- then please explain to me how a true CLT (DISREGARDING ITS AERODYNAMIC CENTRE OF DRAG )machine can PIO/Bunt?

First, PIO: Without an airframe DYNAMIC damper - a good HS - the airframe pitch attitude will not necessarily "track" the rotor's flight path accurately. It may "DYNAMICALLY" swing under the stable rotor - "perfect" CLT, or even perfectly aligned RTV/CG, can still swing in response to turbulence or pilot input. If the airframe is "swinging" under the rotor it has two detrimental effects:

1: The airframe swinging can present misleading pitch attitude/horizon feedback to the pilot - inducing the pilot to perhaps put in unnecessary or destabilizing corrective (reactive) cyclic inputs - PIO anyone?

2: Airframe swinging under the rotor presents a cyclic input to the rotor, as well as a varying and and alternating RTV/CG relationship! Depending on the DYNAMIC response of the rotor to the rate of swinging of the airframe, this may add to more swinging of the airframe, more reaction by the pilot, etc. [Consider the child sitting in the seat of a swing, and starting to swing her their legs at a different rate than the swing wants to swing. When the child hits the right combination of leg swinging rate to the swing natural swinging rate, the swing starts to swing higher and higher. If the leg swinging is out of step (phase) with the swing, the swinging is damped and gets less and less. (Wow, all this "swinging" is making me dizzy! What do you think happens to the pilot when that starts happening in a gyro?)]

The way to avoid this is to provide dynamically damping "feathers" to the airframe. With a good dynamically damping HS, the airframe both tracks the (rotor determined) flight path, AND tracks it quickly so as to cause the airframe to remained essentially "fixed" to the rotor! When this is done strongly, the airframe accurately "tracks" the rotor because of a strong dynamic damping HS that forces the airframe to track the actual flight path, you essentially have a "Fixed Wing" with none of the instability attributes that a non-fixed wing can have.

Case to note: The old French Flea Flicker was actually an attempt to operate the whole main wing separately from the airframe - with the pilot's control stick. this was an attempt to achieve high maneuverability. The Flea Flicker had many of the same problems a gyro has if the airframe is not well stabilized - including PIO!

Now, I can just hear Birdy exclaiming loudly, if I wanted a "Fixed Wing", I'd fly an airplane!!! Not so fast, just because you stabilized the gyroplane by forcing the airframe to track the rotor accurately, that doesn't mean the pilot cannot still maneuver the gyro dramatically by changing the "wing" with the powerful cyclic action of the joystick. The airframe attitude then quickly and accurately "tracks" the new flight path to enhance the precision of the pilot's control. And, additionally, you get the wonderful insensitivity to turbulence that a 300 mph wing can give you!

Second, how can a true CLT bunt?: Any gyro can buntover - especially without a good HS (airframe DYNAMIC pitch damper). All that it takes is for the momentary condition when the RTV is forward of the CG AND, with the rotor experiencing reducing load. The possible momentary condition of the RTV forward of the CG can occur from and for many reasons - here's a primary one:

- A sudden down gust pushes the nose of the gyro lower - nose lower, RTV momentarily forward of the CG. Depending on the degree and rate of the RTV moving forward of the CG - increasing moment arm - compared to the degree and rate of the reducing load of the rotor, the momentary condition can progress into a buntover. Other things are involved, such as the "blowback" and RTV displacement from the changing rotor airflow and pilot control reaction, but if the airframe can pitch too rapidly forward, the progressive nose-down pitching, from reducing forward RTV amplitude, may not be stopped. An Airframe dynamic damper (HS) can slow this airframe forward pitching enough so that the reducing rotor load can offset the increasing forward RTV and stop the nose-down pitching. A good HS will also statically "balance" the down gust load on the gyro's nose, preventing the nose-down pitch action in the first place. But a better DYNAMIC damping HS will actually cause the airframe to pitch nose-up quickly (the stable direction), to provide the corrective cyclic input to the rotor - AUTOMATICALLY and accurately to just the amount needed to correct the down-gust!

Oh my! 4 new posts came in while I was writing this! What have we started?

Thanks, Greg

[gyrogreg]

Don’t you suppose, Greg, that wheels are located in approximately the same relationship to propeller tips whether low rider or high rider and that you might have been fooled by an optical illusion?

Most gyros have 6-12 inches of propeller clearance with the wheels on the ground.

Chuck, I don't think I am fooled by an optical illusion. But, your clearance observation is certainly true - of the prop thrustline offset to wheel drag.

But, to lower the prop thrustline relative to the CG, the CG was raised (higher seat), and the moment arm for the Wheels (to CG) is longer - so more nose-down moment!

Thanks, Greg

[barnstorm2]

Second, how can a true CLT bunt?: Any gyro can buntover - especially without a good HS (airframe DYNAMIC pitch damper).

Greg,

When you make statements like this, I think it would be good for everyone if you clarify that the kind of bunt you are talking about is not a PPO bunt.

Many people don't realize that PPOs are not the only kind of bunt.

As above, Trent almost certainly was asking about a PPO bunt but your answer addressed bunt in the more general sense.

One of the problems with this is that some people then become confused on the conditions of PPO. That is the last thing we need in the sport right now.

PPO bunts are by far the leading killer and problem. Yes, unloading the blades opens up the door for all kinds of bunts, drag-overs and the like.

I certainly sympthize and agree that CLT is far from the only way to make a safe, stable gyroplane and the most important things are static AND dynamic stablity.

I also agree that too many people focus on thrust-line and perhaps ignore the more important issue of dynamic stability (as may be the case in this fatality).

However, lets please not muddy the water about PPOs.

Thanks!

.

[All_In]

Thank you Tim, Just when I think I've got it figured out I see I don't. I am still a little confused regarding bunts.
What other kinds of bunts are there, what problems do they cause other than PPO.

[barnstorm2]

Thank you Tim, Just when I think I've got it figured out I see I don't. I am still a little confused regarding bunts.
What other kinds of bunts are there, what problems do they cause other than PPO.

Bunt-Over: Bunt

A sudden uncontrolled forward tumble about the pitch axis in a gyro; unrecoverable fatal. A bunt-over is a self-sustaining divergent nose-down pitching motion, accelerated and propagated by rapidly changing or diminishing balancing moments on the airframe. Typically, when the nose-down pitch of the airframe and/ or rotor disk reaches a certain point, the nose-down pitching self-perpetuates and accelerates (positive feedback) to result in a full forward tumble. “Power Push-Over is one form of a “Bunt-Over”, but not necessarily the only form of a bunt-over. A “Bunt-Over” is not necessarily a Power Push-Over. Without adequate gyroplane configuration design, a bunt-over can be initiated by wind gust, pilot over-reaction, or sudden power changes

Power Push-Over – PPO:

By definition, PPO is a specific variety of bunt-over that is the result of a high propeller thrustline that is suddenly no longer balanced by other moments on the airframe – thereby, the “power” pushes the nose over downward. Therefore, by definition, a Power Push-Over can only occur in a high propeller thrustline configured gyroplane. But, a PPO is not necessarily the only form of a “Bunt-Over”. A PPO is self-sustaining when the balancing rotor thrust is rapidly decreased at zero or near zero angle of attack of the rotor disk.

Greg in his example illustrates one form of non-PPO bunt.



- A sudden down gust pushes the nose of the gyro lower - nose lower, RTV momentarily forward of the CG. Depending on the degree and rate of the RTV moving forward of the CG - increasing moment arm - compared to the degree and rate of the reducing load of the rotor, the momentary condition can progress into a buntover. Other things are involved, such as the "blowback" and RTV displacement from the changing rotor airflow and pilot control reaction, but if the airframe can pitch too rapidly forward, the progressive nose-down pitching, from reducing forward RTV amplitude, may not be stopped. An Airframe dynamic damper (HS) can slow this airframe forward pitching enough so that the reducing rotor load can offset the increasing forward RTV and stop the nose-down pitching. A good HS will also statically "balance" the down gust load on the gyro's nose, preventing the nose-down pitch action in the first place. But a better DYNAMIC damping HS will actually cause the airframe to pitch nose-up quickly (the stable direction), to provide the corrective cyclic input to the rotor - AUTOMATICALLY and accurately to just the amount needed to correct the down-gust!




Another example occurs in helicopters, known to some as the "Huey-Tuck"

.From Robert Mason's Chickenhawk, page 333. The Tension chapter:

I experimented with the Huey Tuck that day. If the Huey was nosed over too
far on takeoff, the wind resistance on top of the flat roof would force the
nose even lower. The ship would then try to dive into the ground as it
accelerated. IF this happened over level ground, you were trapped in a
vicious circle. Pulling the cyclic back would not overcome the wind pressure
on the roof. Pulling up on the collective to stay away from the ground only
added power to the system, causing you to crash at a higher speed. If you
don't do anything but curse, you hit the ground at a lower speed. Either
way, you lost.

I almost got caught in a Huey Tuck once, and I wanted to know just how far
over was too far. I found out by simulating a level takeoff from a pinacle.

I nosed over very hard and pulled enough pitch to keep the ship flying
horizontal to the ground. I tested the cyclic, and the ship would not
respond. I could feel it happening. Adding power only made it worse. When I
could feel the trap and how I got into it, I knew I could never get into it
by accident. I was experimenting with this over a valley, so all I had to do
to recover was to dive.


.
.

[All_In]

Thank you! You Rock!!!!

[gyrogreg]

@Greg
Is HTL designed into a Magni on purpose?

Actually, John, I think this has always been purposeful. In fact a few years ago they raised the HTL a bit on the M16 - I think to enhance some flight characteristics they liked. At the time, I was surprised to flight test the new configuration to discover no detrimental change in flight static or dynamic stability characteristics. At that time, and with some other information I had seen, I started to invstigate more why my mostly STATIC appreciation of stability apparently had some "holes" in it. That is where my adjusted my focus to DYNAMIC characteristics.

Since then, after getting the chance to do stability flight testing on the Magni M24 (much higher HTL), my conviction that there is MUCH MORE to stability than just these static considerations. (The M24 flight tests to be just as stable with some really nice handling characteristics.)

Some of the reasons, I am guessing, that Magni has intended with HTL:

- Strong Airspeed Static stability - from fairly strong static HS down-load. Nose up moment increases strongly with higher airspeed! (For Engineers - higher negative airspeed feedback in the control loop)

- Tendency to "land itself" in final power reduction in final flare. In the past, I have seen some airplane manufacturers claim their airplane "lands itself". this means that when final power is reduced in final flare, the nose slightly raises and slows down. This does not happen with true CLT. (With LTL, the nose actually lowers with final power reduction, requireing more aft stick to flare.)

- Easier to get in and out of the seat

- Aerodynamics - easier to keep clean aerodynamics when the frontal area is more compact

- Size and weight - easier when airframe members are molre compact - LG, etc.

- Italian styling: Italians probably would not tolerate long and spindly legs - except on the fashion models! They do like smooth curves too!

My only other question currently is if you changed the Magni to CLT how would having it a true CLT effect it in all flight characteristics?

Would making a Magni CLT make it fly any differently = better or worst in any situation you can think of?

True CLT probably would not provide such strong Airspeed static stability at high (power) airspeeds. True CLT would not require HS down-load for airspeed stability - except for the HS down-load that the COD/CG also requires. HTL enhances Airspeed stability at higher power settings - Good, as long as other factors (maintain PIO and buntover resistance!)

Other than the strong airspeed stability above, and the "lands itself characteristic above, and as long as the large HS is employed, I doubt true CLT would affect the flight handling characteristics much. It certainly would make it more difficult to get into though!

Such a strong DYNAMIC damper, IMHO, on any gyro, would make it fly nice - and safely - and mitigate both the otherwise detriments of both HTL and LTL configs.

- Thanks, Greg

[All_In]

Greg, all you guys Rock and have taught me so much... Thank You!!!

[C. Beaty]

I’m not sure there has ever been a verifiable instance of a fatal “dragover.” The majority of fatal accidents are PPOs from HTL gyros.

A flat plate will have ~ 9 lb. of drag per square foot at 60 mph. Rounded shapes, say a human form, will be about ½ as much (a hemispherical cup with rounded side forward, has a drag coefficient of 0.41). With 8 ft² of pilot/pod, we have approximately 40 lb. of drag, which in the case of a high rider, is quite well centered on the CG and thus not an issue.

4.00 x 6 wheelbarrow wheels/tires measure ~ 13” OD x 4” wide and are relatively rounded. That’s a frontal area of 0.36 ft² for each wheel and if the Cd is 0.5, then drag is 1.625 lb. at 60 mph, a total of 3 ¼ lb. for the pair.

If true CLT and the wheels are positioned to provide 10” of ground clearance with a 60” prop, the axle centerline will be 33.5” below the CG. That’s a dragover moment of ~ 9 ft-lb. Struts account for another ft-lb or so. And the beauty is that drag and lift follow precisely the same law; if tail surfaces compensate for drag moments at one speed, they also provide perfect compensation at all other speeds.

Compare propeller force versus drag force: 400 lb of propeller thrust (64 hp delivered by the propeller at an efficiency of 64% with 100 hp going in) and 200 ft-lb of torque @ 2600 rpm prop speed. This is what flips a gyro upside down in a heartbeat in the case of a low rider. Or perhaps rolls it over sideways without compensating propeller slipstream surfaces.

[gyrogreg]

Tim, I finished composing this, then saw your latest post which covered most of this already. But, I am posting this below anyway probably just because I had spent so much time composing it and maybe it is a bit different perspective that might help someone understand these concepts better ----.


Greg,

------ I think it would be good for everyone if you clarify that the kind of bunt you are talking about is not a PPO bunt. Many people don't realize that PPOs are not the only kind of bunt.----
Thanks!

.
Tim, I think you just did! "Buntover" is the more general term for the condition where a decreasing rotor load causes the airframe to pitch and to continue to pitch nose down, which further reduces rotor load, and further pitches the nose down - until the blades flap badly during the rapidly progressing forward flip. This is the result of the flight condition when and where the "effective" RTV is forward of the CG.

The following assumes an adequate HS is not employed to otherwise counter or correct the effects described below:

"PPO", Power Pushover, is the concept or term that presents the incomplete visualization of the prop thrust pushing the nose down when rotor DRAG is lost. There is more to the story than just rotor DRAG - which is why the RTV (Thrust and Drag)/CG relationship is the more accurate set of moments involved. It appears that the term "PPO" was created in an attempt to explain, perhaps in a simplistic terms that more people might understand, what causes a gyro to buntover. Since most buntovers were and are mostly in HTL gyros, the "PPO" visualisation has predominated the perception of what a buntover is, how it happens, and unfortunately and narrowly, what the popularly assumed cause is. My only argument is that HTL is getting a bum rap - it is not the only possible cause of a buntover, and does not necessarily always mean that an HTL gyro will buntover. There are certain advantages to an HTL design, as long as the PPO issue is properly alleviated -with an adequate HS!).

This "PPO" concept also inaccurately infers that a CLT cannot buntover, inferred because a CLT cannot technically "PPO". I don't want to get into Logic 101 here, but "buntover" is not a complete subset within "PPO"! But, "PPO" is a subset of a buntover - just from this visualization of a specific type of buntover. The term "PPO" would not apply unless the assumption is that the gyro has a HTL! But, the "PPO" visualisation is not the only form of, and certainly is not the technically accurate mechanism of any buntover.

"PPO" is more often the type of buntover we commonly see, because so many "gyros" had followed the HTL lead when Bensen gyrocopters were irresponsibly modified with larger props. There are more HTL buntover accidents ("PPO"s) also - because, without adequate HS compensation, they are exposed the to condition of the RTV forward of the CG more of the time - because the HTL is forcing the nose to fly lower almost all of the time. Buntovers can only happen with LTL or CLT when other and more momentary conditions move the RTV forward - such as in a sudden power loss in a LTL - especially at high airspeed. This just doesn't happen as often with a CLT or LTL because, other than in the case of an infrequent sudden loss of power, it likely requires a stronger wind gust or pilot input to initiate a "buntover" in a CLT or LTL.

Take note that, for any CLT, HTL or LTL - without power applied to affect the RTV/CG positioning - the LTL and CLT might tend to be more prone to a buntover at high airspeed than a HTL simply because there may be more aerodynamically draggy things hanging low on the airframe to force the RTV forward of the CG. Without an adequate airframe dynamic damper (HS), it is not good to be in the condition where the RTV is forward of the CG - especially at high airspeed where the rotor load is more sensitive to cyclic (pilot or airframe) input - whether the prop is developing a prop thust moment, or not!

Also, it is my opinion, that a LTL might be more prone to a buntover in a high speed, sudden loss of power situation than a HTL. When power at High power setting is suddenly lost on a HTL gyro, the nose rapidly pitches up - loading the rotor more, not less. For an LTL, a sudden loss of power at high airspeed, will suddenly pitch the airframe nose downward. Since the power loss suddenly also converts the LTL to CLT, and because the airframe nose is pitching lower - the RTV moving forward of the CG, conditions are prime for a continuing buntover. This is all quite complex and depends on, among other things, the rate at which the airframe is able to pitch (HS dynamic damper!), and the action or inaction, and the firm or lack of firm grip of the pilot on the cyclic stick. In all cases, an adequately pitch damping HS is the real answer. Reliance on the illusive CLT is not the real answer. Assumption that CLT is the complete answer is a misplaced confidence that not only puts you in unappreciated jeopardy, but limits the growth of safety and innovation and performance in our sport.

Thanks - Greg

[Jazzenjohn]

Has their ever been a confirmed case of a buntover in a CLT gyro that didn't have floats on it?

Has every buntover been in a HTL gyro?

Is Greg's argument that any gyro can bunt theoretical or actual?

Is it possible to have a rough working relationship of thrustline offset vs tail volume or aerodynamic moment? For instance, x number of additional sq feet per inch of thrustline offset? Just as a rule of thumb?

[C. Beaty]

A sheet of plywood turned broadside to the wind has 285 lb of drag at 60 mph. If its center was attached to the mast 12” below the CG, perhaps we could have a dragover.

Until then, we'll just have to be content with ordinary PPOs.

[Jazzenjohn]

Hmmm... There goes my idea for a combination plywood billboard / windbreak.

Good point Chuck, that would seem to make it a near impossibility the accident was caused by drag over. That also makes sense because if the dragover were actually possible without huge pontoons attached far below the thrustline, it would likely have happened many other times.

It seems we're left with a thrustline/stab issue. Is there a minimum amount of effective stab necessary for even a perfectly CLT gyro? Is there a way to come up with a rough approximation of how much more would be needed as the thrustline changed?

I think it would be interesting to see how much the thrustline/COG changes with different pilots, and different blades. If we assumed a perfectly CLT 600 pound gyro with a 150 pound pilot seated 18" below the thrustline, with 80 pound blades 3.5 feet above the thrustline, and it were changed to a 250 pound pilot and 37 pound blades, how much would the thrustline change?

[gyrogreg]

I’m not sure there has ever been a verifiable instance of a fatal “dragover.” The majority of fatal accidents are PPOs from HTL gyros. -----------------


Chuck, thanks for injecting some real world numbers into this STATIC analysis. And, let's extrapolate this a little further into the static RTV/CG numbers - to move this to the fuller sum of moments interpolation:

Your example of 400 Lb prop thrust, on a gyro with a 2" HTL, would be a moment of 66.6 ft-lb - nose down. This would require a 66.6 ft-lb nose up RTV moment - RTV forward of CG. For a 1000 Lb gyro, that RTV moment arm would be 0.8".

Your example for wheels 33.5" below the CG and a drag of 9 ft-Lb is nose-down moment of about 25 ft-Lb. For the 1000 Lb gyro, this would present a RTV forward of CG moment arm of 0.3". Since drag on this wheel is a function of the square of the airspeed, it would take 100 mph airspeed for this wheel moment to equal the 2" HTL on the prop above.

From this we can certainly see that the RTV-CG moment, as the sole STATIC determinate of buntover potential, shows the 2" HTL to have approximately 2-3 times more buntover potential at 60 mph. I think this advantage for the CLT in this case agrees with accident statistics - especially since there is more exposure time to this STATIC instability situation for an HTL (at all power settings), where the CLT exposure is worst at higher airspeeds.

All of the above presumes there is no HS to STATICALLY balance these nose-down moments.

But, again, this is only a STATIC analysis of the situation. I maintain that DYNAMIC pitch damping, of the rotor and of the airframe, and the interaction between these dynamic characteristics, is also an essential element of the overall stability/safety condition. Take for instance, the M16, which arguably has at least a 4" HTL, and regularly cruises above 100 mph on at least 400 ft-Lb of prop thrust. This gyro exhibits strong static AOA stability, strong Airspeeds Static stability, and highly damped phugoids under these flight, and all, conditions. That safety/stability is verified by thousands, probably millions of flight hours by pilots of all skill levels in all turbulence conditions around the world. Other "clone" models are demonstrating the same. The purely STATIC analysis above cannot explain this.

I'm not trying to tout the Magni here, I'm just trying to help more people understand that there is more to gyroplane flight stability/safety than simple STATIC presumptions. I'm trying to help people understand that the reliable solution is not just a higher seat or CLT. A much simpler and more inclusive solution is a bigger and longer (and more airfoil shaped) tail! When I look at an accident gyro, I don't first look at the seat height - I look at the tail!

A good horizontal Stab, as your post also suggests, can help a lot to offset these STATIC destabilizing moments. But, that same tail's contribution to airframe dynamic pitch damping, is also a major PIO/PPO deterrent. And, the value of that same tail on a longer tail keel is much more improved as a DYNAMIC pitch damper (Square function) than it is as a STATIC balancer (single factor of tail length). But, longer is better for both! And longer reduces the drag penalty of the neccesary down-loaded HS too!

This thread and most others seem to be looking for answers - looking for practical answers that people can believe in. Answers that more easily and completely save lives. I maintain that a good HS is the better, more effective, more practical, and an easier to employ answer than is raising the seat in search of that illusive CLT and the limited advantages that can provide alone. I suggest that the almost total focus and debate on CLT is distracting many from the real answer and unneccessary continuing fatal accidents - and is holding gyros down unnecessarily. Europe and much of the rest of the world, and even the UK CAA (slowly), is learning that - when will America and Australia wake up! When will we stop all this useless wringing of hands and start promoting what can really save lives - focus on a good HS and informed promotion. I will always enjoy trying to understand more completely why this is so, but I think it is time to stop spreading confusion and indecision by arguing about it. IMHO, the CLT, HTL,LTL arguments are near mute if we just do the right thing with a Horizontal Stabilizer! If you like a high seater, fine - do it right with a good HS. IMHO, just don't try to force the illusive CLT on everyone, and present it as their only option.

Thanks, Greg

By the way, IMHO, the answer to the original question in this thread is - lack of adequate HS, and the lack of appreciation the pilot probably had in limits without a good HS. Who’s fault is that - probably not the pilot's!

[C. Beaty]

Greg, the only people I’ve ever heard argue that horizontal tails were unnecessary or even dangerous have been a handful of CFIs and the former FAA official in charge of gyroplanes.

No halfway intelligent person fails to grasp the importance of horizontal stabilizing surfaces once it has been explained to him.

Now for some nitpicking: The example I used for wheels was 4:00 x 6 that had a dragover moment of 9 ft-lb at 60 mph, not 25 ft-lb as you misquoted. One can use turf tires if he wants but I don’t. Whatever the case, it’s not all that relevant if there’s sufficient tail force to compensate.

If a Magni has a 10”-12” offset of propeller thrust line as our friends in Oz measured, something more than a horizontal stabilizer keeps it from tumbling out of the sky. Others say less but I’m not aware of anyone else with hard numbers. I take suppositions in the spirit with which they’re made.

[gyrogreg]

Greg, the only people I’ve ever heard argue that horizontal tails were unnecessary or even dangerous have been a handful of CFIs and the former FAA official in charge of gyroplanes. No halfway intelligent person fails to grasp the importance of horizontal stabilizing surfaces once it has been explained to him.
- Understood, a battle we finally won - so now why the dismissal of a gyro that gets its stability from the proper employment of a HS. Why try to find reasons other than the HS for that stability?

Chuck, what I hear too much is dismissal of the full value of a good HS - mostly because of all the limited focus on STATIC moments and the perception of CLT. I was the first to believe in CLT enough to modify my Air Command into the first High Command. Experience with that, and with a very LTL Dom I built at the time, convinced me that such LTL masqurading as CLT had some pitfalls - such as I nearly ate the runway when I chopped power in the Dom at 75 mph and 10 ft when I was simulating an engine failure after takeoff. Boy it felt good at 90 mph with power on. Boy it was squirly in a 80 mph glide with power at idle. The point is, "CLT" is illusive, and LTL has several drawbacks. The other point is even perfect CLT without a HS has no airframe pitch damper to keep it tracking with, and indicating the rotor flight path. This leads inexperienced pilots to do things that are not right or timed right - PIO. When people understand the full value of a HS, it will cover the issues that an offset prop thrustline can have, while providing the airframe dynamic pitch damping that CLT can't provide. At the same time, it can statically balance and compensate some of the prop and drag offset.

Now for some nitpicking: The example I used for wheels was 4:00 x 6 that had a dragover moment of 9 ft-lb at 60 mph, not 25 ft-lb as you misquoted. ..

I stand corrected - I double dipped the moment arm when I figured your "9" for 9 Lb, not 9 Ft-Lb.

One can use turf tires if he wants but I don’t. Whatever the case, it’s not all that relevant if there’s sufficient tail force to compensate.

Now your talking! But that is still just talking the STATIC benefit of the HS.

If a Magni has a 10”-12” offset of propeller thrust line as our friends in Oz measured, something more than a horizontal stabilizer keeps it from tumbling out of the sky. Others say less but I’m not aware of anyone else with hard numbers. I take suppositions in the spirit with which they’re made.

Chuck, you're a smarter guy than me with the equations and lift calcs. How about running some numbers to just see what the DYNAMIC forces on the HS tail might be when the tail is rising in the airflow:

- Estimate a reasonable MOI for Magni M16. MT wt = 600 Lb, pilot = 250 Lb, engine about 150 Lb, Passenger and fuel on CG.
- Apply a nose down RTV moment equivalent to a 10" prop offset moment
- Determine the pitch acceleration with that moment applied to that MOI (this presumes the RTV goes from 1 to zero G instantaneously.
- Maybe determine the pitch rotational velocity one second later - then 2 seconds later, then 3 seconds later
- At each of those pitching rates, determine the HS lift resisting that pitch rate due to it's vertical movement in the airflow (increased relative wind on the HS)

Would this give us some clues as to if the DYNAMIC response of the HS - to the likely pitching rate is enough to slow or damp that pitching rate. Or, would this hint that there is still something else at work here?

***** Another approach:

Flight testing verifies that the Magni M16 does indeed have Phugoid oscillations - indicating it has an AOA restoring moment - a spring, if you were, restoring AOA when it is not neutral, That restoring force would be the HS deflected in the airstream - and the reason it has phugoid oscillations.

- The natural phugoid oscillation freq for the Magni M16 is measured as a period of about 14 seconds

- Using the aerodynamic forces on this size tail, and the max pitrching rate velocity in the oscillation, is it possible to calculate backwards to determine the DYNAMIC damping component of HS lift - 90 degrees leading in phase to the displacement oscillations - in phase with the pitching oscillation rate.

Just want to see if the Dynamic response of the HS - it's lift component due to its vertical movement, would be enough on its own to cause this rate of phugoid oscillation - or is there something more at work here.

Let me know if you want to tackle this calc - I can feed you some more numbers from the gyro - HS size, moment arm, etc.

- thanks, Greg

[Vance]

- Understood, a battle we finally won - so now why the dismissal of a gyro that gets its stability from the proper employment of a HS. Why try to find reasons other than the HS for that stability?

Chuck, what I hear too much is dismissal of the full value of a good HS - mostly because of all the limited focus on STATIC moments and the perception of CLT. I was the first to believe in CLT enough to modify my Air Command into the first High Command. Experience with that, and with a very LTL Dom I built at the time, convinced me that such LTL masqurading as CLT had some pitfalls - such as I nearly ate the runway when I chopped power in the Dom at 75 mph and 10 ft when I was simulating an engine failure after takeoff. Boy it felt good at 90 mph with power on. Boy it was squirly in a 80 mph glide with power at idle. The point is, "CLT" is illusive, and LTL has several drawbacks. The other point is even perfect CLT without a HS has no airframe pitch damper to keep it tracking with, and indicating the rotor flight path. This leads inexperienced pilots to do things that are not right or timed right - PIO. When people understand the full value of a HS, it will cover the issues that an offset prop thrustline can have, while providing the airframe dynamic pitch damping that CLT can't provide. At the same time, it can statically balance and compensate some of the prop and drag offset.
- thanks, Greg

Hello Greg,

It puzzles me that the safety record of the Magni suffices for your proof that it is not dangerous with a very large high thrust line offset and yet you continue to suggest that a small low thrust line offset has these terrible defects.

As far as I know no one has been killed in a low thrust line gyroplane because of this power off nose down pitching moment that you perceive as so dangerous.

The Dominator that you had this power off near miss in was not a two place tandem that handles like a truck.

I feel that making up perceived defects about other designs does not make your Magni seem any better designed.

Calling centerline thrust elusive does not seem relevant to me if Magni didn’t even try.

I feel that these static moments are a nice way to quantify the things that go into this dynamic system. In my opinion the perturbation that is being dampened by the horizontal stabilizer is the result of these static measurements that you seem now to discount.

I am not an engineer. I don’t pretend to be an expert on gyroplanes. I do recognize when what you describe does not align with my limited flying experience and my reading of the NTSB reports.

Thank you, Vance

[C. Beaty]

The only attempt at rigorously investigating dynamic behavior of a gyro where mathematical analysis was compared with measured data was the Glasgow research.

I don’t see anything wrong with Glasgow’s analysis but more importantly, Raghu Arunachalam, far more competent at math and physics than I, didn’t either.

[Aussie_Paul]

Trying to clarify...

The accident gyro appears to be HTL.
Do we have the exact measured amount of HTL???
From my testing the pod accentuated the need for an effective H/S.
The reasonably inefective H/S far too small for open frame and MUCH too small for a pod equipped gyro.
The evidence suggests PPO.

SO, could we have a pilot incapacitation with the pilot slumping forward to initiate this sequence of events in a gyro that was not built as stable as it could have been???

I am saying this to bring some reality back to this discussion.

I am no expert but I have been around a while conducting considerable testing in this area of the gyroplane flight envelope.

Aussie Paul. :)

[flying-i]

See end of page 3.
http://www.caa.co.uk/AANDocs/28705/28705000000.pdf

Exerpt:
T23 Load Distribution Limits
MGL report 038-00-16C Weight and Balance Test Procedure details Cc/Thrust
offset as varying between 8.4 inch and 11 inches (Thrust line 8.4 inches above to 11 inches above CG).

How does this happen?

[C. Beaty]

See end of page 3.
http://www.caa.co.uk/AANDocs/28705/28705000000.pdf

Exerpt:
T23 Load Distribution Limits
MGL report 038-00-16C Weight and Balance Test Procedure details Cc/Thrust
offset as varying between 8.4 inch and 11 inches (Thrust line 8.4 inches above to 11 inches above CG).

How does this happen?Thanks –very interesting.

It would be informative to pull up the matching document for the ELA but so far, I’ve had no success.

[Heron]

I would like to see hipotetical situations with a Magni that, having same config, can produce another 30/50 hp of power . . .throttle operation wise.
Or any of the lookalikes.
thanks
Heron

[flying-i]

Seems the MT03 thrust line also varies (from 3.91 inches to 9.44 inches above the CG)?

See page 3, above point 5.2 in the link below:


http://www.caa.co.uk/AANDocs/29134/29134000400.pdf

[Jazzenjohn]

In my opinion, the reason there is such variability in the thrustline numbers is because in the cases of the Magni and MT-03 they are HTL gyros that are both 2 seaters and the combination of fuel and pilot load when both the fuel and especially the seating positions are far from the thrustline there can be a big difference between a single 170 pound pilot and 2 300 pound pilots when the seat is 15 or 20 inches below the thrustline. On a high seater like the Dominator the pilots seating position is very near the thrustline and changes the vertical CG far less. Pilot weight would also be a bigger factor on gyros that have a somewhat low seating position but are nearer CLT by virtue of a very heavy rotorhead/rotor/prerotator system.

It would be helpful if we could get the accident gyros rotor type and pilot weight and compare it to the thrustline test that was performed. It would be even better if we could get weights and measurements of a similar gyro. Doing a quick and inaccurate guesstimation, I can come up with a thrustline offset change from a light to a heavy pilot and blade switch that would change the thrustline offset by as much as 6 inches.

[C. Beaty]

Thanks, -i; very interesting.

The stepped keel has helped the MT-03 but not enough.

[bosca]

Hi all,
As to the conclusions or part of (ozz accident) would for instance the weighted DW's help with the stabilasion of our gyro in relation to PPO and bunt over etc.Would the weighted tips help stabised the HTL gyro to some extent.
Kym.

[Greg Mitchell]

http://www.asra.org.au/smf/index.php?topic=3170.msg23121#new

[gyrogreg]

I feel that making up perceived defects about other designs does not make your Magni seem any better designed.

Vance, your post disturbed me. So, I went back and reviewed all my posts in this thread to see if I had strayed from my principles of promoting better understanding of what makes gyros safer. I do not think I presented anything that was not an objective explanation of what I believe are valid observations about configuration issues. Where I knew there might be some ruffled feathers, I use the disclaimer that those thoughts were “IMHO”. Where I pointed out some PIO or buntover issues with CLT or LTL, was when I was asked specifically to do so.

I will admit that I failed in this thread to convey my end thoughts on all this – that you can’t evaluate the stability or PIO or PPO/Buntover susceptibility by simply looking at a gyro – or even measuring it’s prop thrustline or HS parameters. My mantra has always been that the final result is too complex to analyze on paper, or with any “cookbook” paradigms. A gyro MUST be flight tested to evaluate its full stability characteristics – including Static AOA and Airspeed stability, and Dynamic Stability. You need that data to make any real conclusions. Since this thread was asking for answers related to an accident gyro, it would not do much good to say go fly it and test it!

Initially I decided to interject my thoughts into this thread when I saw it leaning toward rules to force CLT on everyone – the "knee jerk" Big Brother approach! THAT, needs comment! The gist of all my posts here was to emphasize that dependence on the “illusive” CLT is not the full answer, or always the proper answer in some situations – since “CLT” is often really “LTL” with definite issues.

Hello Greg,
It puzzles me that the safety record of the Magni suffices for your proof that it is not dangerous with a very large high thrust line offset and yet you continue to suggest that a small low thrust line offset has these terrible defects.

I would not say that the accident record “suffices” for proof; I would say that is the proof. The question we were asked in this thread was how to avoid such tragedies. The accident record IS proof of improved safety! I see now that this accident gyro was fairly CLT! What does that prove?

As far as I know no one has been killed in a low thrust line gyroplane because of this power off nose down pitching moment that you perceive as so dangerous.

Now here is where I am going to raise some fur! I am passionate about this subject because a friend or ours in CH 35 was killed a few years ago in a “CLT” gyro. Although the apparent consensus is that the instructor/pilot in this gyro must have had a medical problem, IMHO, this gyro apparently had an Airspeed stability problem – it dived faster and faster, steeper and steeper into the ground. Unconscious pilot or not, limited stick travel or not, any aircraft should not have runaway airspeed. It should maintain the airspeed it is trimmed for! Static Airspeed instability is a form of Static AOA instability – susceptible to buntover. The runaway airspeed, Airspeed Static instability is a form of a buntover – just a buntover that is slowed in pitch by a fairly good dynamic damper – a fairly large HS! The Airspeed and AOA instability, IMHO, was the result of this “CLT” “band aid”, really being LTL. This gyro probably has an adequate dynamic damping HS to avoid buntover, but it was not enough to avoid airspeed runaway! This gyro does have a BIG HS, but it is shaded behind the large enclosure and, IMHO, looses significant ability to counter the LTL moments when power is reduced. Pilots report that this gyro, with power reduction, lowers its nose and builds airspeed – and once over about 80 mph is difficult to recover with cyclic stick only. That this gyro was LTL has been confirmed by three pilots experienced in this particular model gyro – if you want more information on this, ask Stan Foster. Sorry, I may be a bit bitter about losing this friend! It didn’t have to happen, but I might harbor a little resentment that the ultimate cause was trusting “CLT” more than a good HS!

Want some more fur! The Adler fatal accident in Colorado several years ago: This was a “CLT” that “by definition” could not PPO. But, evidence is that it did buntover – rotor separated in air, etc. This gyro was actually badly LTL – Mr. Adler was trying to make it as LTL as he could – isn’t that a good thing to do? At the time, Chuck B. even commented – “Too much of a good thing is not good”. The NTSB reported drugs or some medical problem, but drugs or not, gyros should not buntover! A gyro should not depend on the pilot to prevent buntovers! We’ve had other CH. 35 friends over the years that had fatal PPO accidents – in Bensen Rotax style without adequate HSs. Those losses are what stirs my passion to not sit by quietly when I see the sport taking a wrong turn! That was about the time I decided to learn all I could about the cause of such accidents in the sport I love, and to become an instructor to help people learn about how to avoid them!

So, I guess I am saying, Vance, I don’t feel like apologizing for stirring some fur once in a while!

Calling centerline thrust elusive does not seem relevant to me if Magni didn’t even try.

??? - Apparently, Magni didn’t need to try – they had other tools in their toolbox. Look at the posts above about the Magni and the MT03 thrustlines – apparently thrustlines are “illusive”. That is a lot of variance. I guess fuel levels or pilot weights don’t change on single seaters – so their “CLT” would stay CLT all the time? CLT is "illusive" on any gyro! Small and light single seaters with lower MOIs, as you suggest, are even more prone to rapid pitch reactions if their prop thrustlines happen to be offset! With the HTLs on the Magnis, and MT03s (and on the ELA clone), where are all the smoking holes? My point has been that you can’t assure you always have CLT, so I suggest you should be considering using a good and long HS to make sure. Or better yet, go up and flight test Dynamic stability and determine the safe stability flight envelope, and what its limits are! Too bad someone can’t do that for this gyro and pilot!

That’s what we ought to mandate – identify the safe stability flight envelope, and then fly within it! Don't mandate "prescriptive" band aids that can't assure safety anyway - they all need to be flight tested before violating the safe flight envelope.

I feel that these static moments are a nice way to quantify the things that go into this dynamic system. In my opinion the perturbation that is being dampened by the horizontal stabilizer is the result of these static measurements that you seem now to discount.

You are correct, the perturbations that need to be damped by a HS, do result from an imbalance of the static moments. I don't discount static measurements, I just say you can't count on them. They are too "illusive", they change with airframe AOA, with loading, with power, and too many variables that can't be well quantified. Use them as a starting point to avoid some unwanted pitch sensitivities to power, but don't trust your life on them! But, the static moments, especially the transient moments from a disturbance are way too difficult to assure under all conditions. Since you can’t assure there aren’t any bad pitch moments all the time, my advice is to compliment your gyro with a good HS dynamic pitch damper to be much more sure whatever the static moments are – then they won’t matter much. Apparently they don’t matter much on some pretty HTL gyros with strong airframe dynamic dampers!

Thanks, Greg

I am not an engineer. I don’t pretend to be an expert on gyroplanes. I do recognize when what you describe does not align with my limited flying experience and my reading of the NTSB reports. Thank you, Vance

For the record, I’m not an Aeronautical Engineer either. I was an electrical Engineer and my opinions on aircraft stability are derived from an understanding of control systems, feedback, frequency responses, etc. – electrical and control systems analogies that I find insightful into our gyro stability issues. My experience also includes building and modifying and flying many hours in an Air Command then converted to a High Command ("CLT"?), building and flying a Dominator, and training many new students in Magni gyros - almost 25 years and over 2500 hours in gyros - and dozens of years in airplanes and FW ultalights. I am also the ASTM Gyroplane subcommittee chair with inputs and conversations with many gyro fliers, gyro and FAA technical experts, and airplane and helo professional test pilots that contributed to the ASTM gyroplane standards development.

[RotoPlane]

I for one look forward to reading these "new rules regarding vertical centre of gravity/thrustline positions and the size, placement and shape of horizontal stabilizers". I applaud the ASRA and even though they will not be a requirement in the USA, I believe in the common-sense value of the above rule statement, and will see to it that my gyro will meet or exceed them……hopefully it already does…..

[gyrogreg]

I disagree with "prescriptive" fixes such as prescribing the prop thrustline offset or even the HS parameters. It is much more complex than this! The real solution is to require Static and Dynamic flight testing to identify the safe flight envelope. Flight testing will identify any issues with that gyro - much better than hanging a gyro at strange attitudes.

As an example, the fatal accident gyro I mentioned in my (long) post above, would probably meet any of the parameters that anyone could come up with - it's prop thrustline is, I am told, only about 2" LTL. And, the enclosure disturbance to the HS airflow, and the HSs variability with propwash, effects on this gyro's huge HS could only be identified by flight testing.

During our development of the ASTM gyroplane standards, the US FAA was adament that it should not "prescribe" solutioins such as defining the HS parameters or the offset of the prop thrustline. There are too many variables that affect both of these, including the dynamic characteristics. Formulas to effectively "prescribe" a HS and prop thrustline would be far more complex, and with too many variables to compute with any degree of results accuracy. And, making simple mandated parametes would be too limiting to gyro or safety advancement.

(I beleive it has been reported in this thread that this accident gyro was actually CLT??)

For instance, the MTs and Magnis and ELAs would never comply with some sort of CLT tolerance, unless that thrustline formula included a lot of other unknown parameters that could never be quantified. And, these models are demonstrating worldwide that they have a good solution to gyro stability safety!

Prescribing solutions in mandated standards is a mistake. Mandate performance results - flight testing instead! The UK is certifying gyros per such flight testing - even if those gyros do not meet their recommended 2" prop thrustline offset! They are finally getting it right in Britain!

Thanks, Greg Gremminger

[Aussie_Paul]

Greg said,Prescribing solutions in mandated standards is a mistake. Mandate performance results - flight testing instead! The UK is certifying gyros per such flight testing - even if those gyros do not meet their recommended 2" prop thrustline offset! They are finally getting it right in Britain!

Thanks, Greg Gremminger

I agree. Mandating physical and not performance regs discriminates against "experimenting". If someone were to meet the performance parameters with a brick tied to a rope trailing 50' behind the gyro then that should be passed.

Not well explained but I am sure you get my drift. That was why I was very supportive of the ATSM (??sp) standards

Aussie Paul. :)

[RotoPlane]

Greg and Paul - I agree with what you are both saying and that is why I said common-sense rules. But….there must be some way in these rules to define appropriate sizing for components and locations, so that for instance a HS isn't a 2 sq.ft. barn-door when it should be a 5 sq.ft. airfoil to operate correctly. Or we will be right back where we started in this thread……

[karlbamforth]

All you really need is a statement something like this..

If requested and appropriately substantiated, EASA can approve
Alternative Methods of Compliance

This was cut/paste from an EASA AD.

Basically they tell you why you have to do it and list what you have to do, fit 50 sqft tailplane have CLT etc. then just say but if you want to do something else then prove to us it works.

Most ppl follow the recomendations but the last line allows a different approach as long as you can prove compliance with the intention of the ruling, in this case stability.

This is basically how high thrust line gyros like the MT's and Magni's, can be approved in UK despite the +-2" of CLT required in Section T.

[Vance]

In my opinion a large horizontal stabilizer placed well back from the center of gravity has value in gyroplane stability. I have found that I prefer gyroplanes of this configuration.

I found the closer to center line thrust I got the better I liked the way the Predator flew and particularly landed.

In my opinion getting near centerline thrust with a gyroplane is not “elusive” or even particularly difficult.

I have flown high thrust line gyroplanes and low thrust line gyroplanes. If for some reason I needed to have a defective thrust line I would prefer it on the low side.

I love climbing up into the Predator and it is ok with me if some people think she looks funny.

Mariah Gale will have the Pilot and the passenger sitting even further off the ground than the Predator.

Thank you, Vance

[C. Beaty]

Now here is where I am going to raise some fur! I am passionate about this subject because a friend or ours in CH 35 was killed a few years ago in a “CLT” gyro. Although the apparent consensus is that the instructor/pilot in this gyro must have had a medical problem, IMHO, this gyro apparently had an Airspeed stability problem – it dived faster and faster, steeper and steeper into the ground. Unconscious pilot or not, limited stick travel or not, any aircraft should not have runaway airspeed. It should maintain the airspeed it is trimmed for! Static Airspeed instability is a form of Static AOA instability – susceptible to buntover. The runaway airspeed, Airspeed Static instability is a form of a buntover – just a buntover that is slowed in pitch by a fairly good dynamic damper – a fairly large HS! The Airspeed and AOA instability, IMHO, was the result of this “CLT” “band aid”, really being LTL. This gyro probably has an adequate dynamic damping HS to avoid buntover, but it was not enough to avoid airspeed runaway! This gyro does have a BIG HS, but it is shaded behind the large enclosure and, IMHO, looses significant ability to counter the LTL moments when power is reduced. Pilots report that this gyro, with power reduction, lowers its nose and builds airspeed – and once over about 80 mph is difficult to recover with cyclic stick only. That this gyro was LTL has been confirmed by three pilots experienced in this particular model gyro – if you want more information on this, ask Stan Foster. Sorry, I may be a bit bitter about losing this friend! It didn’t have to happen, but I might harbor a little resentment that the ultimate cause was trusting “CLT” more than a good HS!It is only human nature to massage the evidence until it fits our prejudices.

Here’s the first recorded example of runaway airspeed in a “CLT” gyro from Cierva Autogiros by Peter W. Brooks:

“The first fatal accident to an Autogiro in Britain, referred to earlier, occurred to a Rota (C-30) of No. 2 (Army Co-operation) Squadron of Old Sarun on January 21, 1935. The pilot, Flying Officer L.W. Oliver, was killed when he lost control of his aircraft while flying in cloud and got into a high-speed dive from which he was unable to recover before he hit the ground.”

“…..This experience of Marsh’s (on a floatplane C-30) was attributed at the time to partial unsticking and lifting of the plywood skinning of the Avro-manfactured blades. It was said that this altered the blade profile at high-speeds and caused the nose-down pitching moment. Brie had experienced a similar phenomenon while diving a landplane C-30 during its Certificate of Airworthiness tests at Martlesham Heath some time before. He also had found, during a gentle dive, that the nose suddenly dropped more and more and that he was unable to prevent it. He throttled back and the machine leveled out before reaching a dangerous attitude.

“It seems from these incidents that the C-30 had a tendency to pitch nose-down uncontrollably when dived above a certain speed (apparently about 115 mph, 185 km/h). This was, in fact, due to twisting of the highly cambered blades of Gö 606 aerofoil section, as confirmed by the NACA in the United States about three years later, during tests on a Kellett YG-1B, which had blades of the same section….”

The Sparrowhawk to which Greg refers has the cabin pretty well centered on its CG, so “dragover” from that source isn’t an issue.

If the drag moment from wheels and struts is balanced is by the horizontal tail at 40 mph, it is also balanced at 100 mph. Whatever the case, wheel drag isn’t much of an issue. I don’t know the dimensions of a Sparrowhawk but say the wheels/tires are 5” x 16”, giving a frontal area of 1.11 ft². The total drag at 100 mph with a Cd of 0.5 would be 13.8 lb. for the pair. Likely balanced by drag of rotorhead, hub bar and upper mast. The “dragover” theory doesn’t wash.

The pilot of this particular aircraft had been having trouble with trim. He had made several trips to a local hardware store to purchase stiffer trim springs.

[birdy]

--------------------------------------------------------------------------------

You’ve never heard of a flying wing, Birdy? (but it is pretty tricky to get one to work)
Yes CB, i have, but thats not wot Kym was talkn bout.

--------------------------------------------------------------------------------

Bird,Are you suggesing to me that you fly without a HS with 100% control.
Yes, why wouldnt i have 100% control?

Havent you moved on??
From where?

Must be very confusing to those new to the sport to hear you make such a statement.
I dout it Kym, most people read wots rit, not wot ever it is you put between the lines.

A Bloody dangerous illusion your creating Bird.
Zat rite?
Care to clarify why?

[gyrogreg]

The Sparrowhawk to which Greg refers has the cabin pretty well centered on its CG, so “dragover” from that source isn’t an issue.

If the drag moment from wheels and struts is balanced is by the horizontal tail at 40 mph, it is also balanced at 100 mph.

Chuck, Certainly this is theoretically correct to say this. BUT, it is not this simple: The wheels are (probably) exposed to the free airstream and their drag is proportional to the square of the airspeed. Theoretically, if the HS is exposed also to that same free airsteam, it's balancing down-lift would exactly compensate the wheel nose-down moment at all airspeeds - as you say.

BUT!!! The HS on this gyro is not in clean air - it is behind the enclosure, it is behind the prop. It is VERY difficult to say what the airflow on the HS could be. Airflow on the HS would be at least disturbed, if not deflected vertically and changing dramatically with different airspeeds. You cannot say this HS would have the same relative wind speed and direction as the wheels.

BUT, also, this HS is highly immersed in the propwash. This means that it will be much less effective when power is not applied, than when it is applied - not to mention what the propwash does to the disturbed air coming around the enclosure.

At the time of this accident, the designer said they went a bit too low with the prop thrustline on this gyro. (I'm not condemning the gyro or designer, this just emphasizes that "CLT" is illusive and dificult to control for all loading and flight conditions.) At least two experienced owner/pilots of this tiype confirmed afterwards that this gyro had a tendincy to increase it's trimmed airspeed when power was reduced - speeds up. This is the telling halmark of an "effective" LTL configuration.

Those same two pilots reported that, when power was reduced from a cruise condition, without pilot corrective control, the airspeed started and continued to increase. That is the telling halmark of Static Airspeed instability - a version of Static AOA instability that is tempered by the HSs ability to dampen any rapid pitching - prevent an actual buntover. These two pilots also reported that, if airspeed was allowed to increase over about 80 mph, the stick forces to recover became excessive and discouraged the pilots from wanting to pull that hard to stop the dive. Dive recovery was accomplished by ADDING power - non-intuitive, but another halmark of LTL.

Now, in the scenario in my mind of what happened on this accident, the pilot/instructor, as has been suggested, must have become incapacitated. Our friend, the low time student, might then have been presented with an increasing airspeed dive - as observed by the witness. As airspeed increased, the intuitive thing that the student would have done would be to reduce the throttle to slow down. But, in this LTL case, that only increased the airspeed and steepend the dive, Once the airspeed exceeded about 80 mph, the stick would be very heavy, and the student probably could not have anticipated he had to ADD power to slow down! That is a charactristic of LTL gyros that is completely non-intuitive and must be learned and practiced.

Now, maybe I'm messaging the evidence to fit a "prejudice". But, the above gyro characteristic has been verified by flight testing - these two pilot/owners. The other alternative causes in this accident are something in the controls broke, or the pilot dove into the ground on purpose. Evidence and the manufacturer denies the controls failed, and no one would believe the pilot did this on purpose.

Maybe I am prejudiced, but problem characteristics with any aircraft should be remedied. IMHO, they are correctable. In this case, I am certain this issue would be entirely correctable if your simple statement that "the drag moment from wheels and struts is balanced is by the horizontal tail at 40 mph, it is also balanced at 100 mph" were true. But, unfortunately the real world is more complex than this. Maybe your statement might be more correct if that HS were more exposed to undisturbed airflow, and sized so it did not depend on propwash for adequate effectiveness.

My point is that it is very difficult to solve all the issues with purely STATIC analysis. The DYNAMIC benefits of a strongly pitch damping HS will reduce or eliminate those issues - as it apparently does with MTs and Magnis. But, my more basic point is that, no matter what configuration you end up with, it is not proven stability safe until you test it for both STATIC and DYNAMIC stability. These flight tests are simple and safe, and they will easily identify the safe stability (airspeed/power) envelope within which that gyro should be limited.

Thanks, Greg

PS: Chuck, When I first decided to try to do something about all the unnecessary fatal accidents in gyros - back in the early '90s - you were my inspiration and knowledge source. You were a main reason I also focussed on and experimented with both CLT and LTL, and "T" tails with highly embedded HSs. It does pain me now to feel I need to take issues with some of these principles. But, my experiences since the '90s with the Magni, with training dozens of new pilots in the Magni (and, for a while training students to fly less stable gyros - frustrating!), and my involvement with many diverse perspectives and prejudices in our ASTM gyro work, has convinced me that we need to widen our view of just how to improve safety in gyros - beyond the purely STATIC analysis. And, beyond any admirable but impossible attempt to purely provide formulas and prescriptions to try to identify stability characteristics on paper. It's fun, but not practical! The better way is to do all you can on paper, but not depend on it. Depend on flight test results. The final proof of the pudding, IMHO, is the accident record which is hard to dispute and what our real goal is!

[StanFoster]

Greg- I am just repeating what I told you earlier. I did your stability tests in ny SparrowHawk, two of the three tests passed. But the one test where the gyro was trimmed to fly hands off around 60 or so did not. If I recall correctly , the speed should stabilize within 10 % of the trimmed airspeed when the power was smoothly removed. My SparrowHawk would always point downward at a steep angle when the power was removed. I distinctly rememeber going for my firsy SparrowHawk ride in Terry Eilands SparrowHawk. I was flying it and asked Terry if I could do some aggressive maneuvers. He ok'd it and the first thing I did was chop the power. I was surprised how much the nose dipped and how much backstick it took to do a power off turn. Anyway, when I did the power off speed stability test in my SparrowHawk, I wanted to pretend that I had lost my backstick, and just rode along to see what would happen. I was trimmed at 60 so it should stabilize around 66 to be at 10% increase. I knew that wouldn't happen, and as I kept my hand off applying any backstick, I watched my nose head down sharply, as my airspeed went through 70, then 75, then 80, then 85 , and as I went through 90, I cried uncle and saved it with backstick. I am not smart enough or experienced enough to let this gyro continue on a further runaway airspeed. I know if I had applied power, the nose would have come up. But here is my thinking on Terry and Bills accident. If say they had lost backstick, and Terry reduced power like would likely happen, the SparrowHawk would enter a nosedown runaway airspeed situation if power were not applied. I can see it would be hard to add power when you are diving at a high speed anyway! Steve McGowan had offered strong advice how to get out of this situation with a locked backstick and in a dive. He said to kick the rudder in hard, get going sideways, and use sidestick to get the airspeed under control. I practised this, but I was too timid on giving it hard rudder and going sideways. I was not experienced enough in this kind of flying but I have no doubt if anyone could have saved Bill and Terry, it would have been Steves ability. Stan

[C. Beaty]

Greg, the rotor plays a vital but often overlooked roll in speed stability because of its velocity stability; the blowback effect or to be technical, the derivative of pitching moment with regard to flight path speed.

A Sparrowhawk equipped with a rotor having zero pitching moment coefficient can’t “runaway”. With a power chop, it will pitch nose down and stabilize at some higher speed because of the LTL. But not runaway as described for the Cierva C-30s by author Peter W. Brooks.

The rotor also plays a vital role in angle of attack stability. Tail heavy rotorblades cause angle of attack instability while nose heavy rotorblades produce stability. In a sense, the same nature as a FW with aft or forward CG.

A large part of the behavior of a Magni is caused by the rotor. I’m not certain whether it’s caused by blade sweep, overbalance or what. However, experienced pilots indicate something very different in happening with a Magni rotor system. Just recently, one very knowledgeable pilot described the sensation as one of the stick being anchored in concrete against rapid motion but OK for slow movement.

Certainly, all flying machines need horizontal tails but to compensate for large errors of thrustline offset is no more than a bandaid. Why carry an extra burden when it is unnecessary?

[Doug Riley]

I think that the reason we end up talking past one another on these issues is that we have not specified who the audience is. Different proposals for design formulas, rules-of-thumb or regulations are based on different assumptions about who will read them.

A test-results requirement is fine for an aeronautically knowledgeable design team. They will know how to create airspeed stability, without needing paint-by-numbers instructions ("Here, Johnny, you can EITHER put a humungous loaded HS back HERE or a littler one THERE and stick your thrustline right on the CG.").

The other audience, though, is composed of shade-tree mechanics -- often ones with an irrational macho attitude. Ignorance AND attitude make for a very dangerous brew. These folks may be fun at a pig roast, but they will NOT know what to do if you tell them that they must design to achieve airspeed stability. In fact, they will most likely take offense at all your big, eggheady words* and deliberately ignore you.

If, OTOH, you tell them to design in CLT and a HS at least SO big, partly immersed in the propwash, you have some slight chance of it sinking in.

I think we need a test-result standard, but also simple rules of thumb that will allow unqualified "designers" at least to get close to compliance. Like it or not, unqualified designers are the core of the homebuilt aircraft community. They are not going away, and most of them are not going to become dramatically smarter. Are we dumbing down the science? You betcha.

Sorry to blab the family secret.

______________________
* One much-beloved gyro CFI refers to people who use technical language regarding gyro design as "paper a**holes." This is what we have to contend with.

[Resasi]

Doug, a touch of levity, with a serious message was very welcome.

[Vance]

Chuck, Certainly this is theoretically correct to say this. BUT, it is not this simple: The wheels are (probably) exposed to the free airstream and their drag is proportional to the square of the airspeed. Theoretically, if the HS is exposed also to that same free airsteam, it's balancing down-lift would exactly compensate the wheel nose-down moment at all airspeeds - as you say.

BUT!!! The HS on this gyro is not in clean air - it is behind the enclosure, it is behind the prop. It is VERY difficult to say what the airflow on the HS could be. Airflow on the HS would be at least disturbed, if not deflected vertically and changing dramatically with different airspeeds. You cannot say this HS would have the same relative wind speed and direction as the wheels.

BUT, also, this HS is highly immersed in the propwash. This means that it will be much less effective when power is not applied, than when it is applied - not to mention what the propwash does to the disturbed air coming around the enclosure.

At the time of this accident, the designer said they went a bit too low with the prop thrustline on this gyro. (I'm not condemning the gyro or designer, this just emphasizes that "CLT" is illusive and dificult to control for all loading and flight conditions.) At least two experienced owner/pilots of this tiype confirmed afterwards that this gyro had a tendincy to increase it's trimmed airspeed when power was reduced - speeds up. This is the telling halmark of an "effective" LTL configuration.

Those same two pilots reported that, when power was reduced from a cruise condition, without pilot corrective control, the airspeed started and continued to increase. That is the telling halmark of Static Airspeed instability - a version of Static AOA instability that is tempered by the HSs ability to dampen any rapid pitching - prevent an actual buntover. These two pilots also reported that, if airspeed was allowed to increase over about 80 mph, the stick forces to recover became excessive and discouraged the pilots from wanting to pull that hard to stop the dive. Dive recovery was accomplished by ADDING power - non-intuitive, but another halmark of LTL.

Now, in the scenario in my mind of what happened on this accident, the pilot/instructor, as has been suggested, must have become incapacitated. Our friend, the low time student, might then have been presented with an increasing airspeed dive - as observed by the witness. As airspeed increased, the intuitive thing that the student would have done would be to reduce the throttle to slow down. But, in this LTL case, that only increased the airspeed and steepend the dive, Once the airspeed exceeded about 80 mph, the stick would be very heavy, and the student probably could not have anticipated he had to ADD power to slow down! That is a charactristic of LTL gyros that is completely non-intuitive and must be learned and practiced.

Now, maybe I'm messaging the evidence to fit a "prejudice". But, the above gyro characteristic has been verified by flight testing - these two pilot/owners. The other alternative causes in this accident are something in the controls broke, or the pilot dove into the ground on purpose. Evidence and the manufacturer denies the controls failed, and no one would believe the pilot did this on purpose.

Maybe I am prejudiced, but problem characteristics with any aircraft should be remedied. IMHO, they are correctable. In this case, I am certain this issue would be entirely correctable if your simple statement that "the drag moment from wheels and struts is balanced is by the horizontal tail at 40 mph, it is also balanced at 100 mph" were true. But, unfortunately the real world is more complex than this. Maybe your statement might be more correct if that HS were more exposed to undisturbed airflow, and sized so it did not depend on propwash for adequate effectiveness.

My point is that it is very difficult to solve all the issues with purely STATIC analysis. The DYNAMIC benefits of a strongly pitch damping HS will reduce or eliminate those issues - as it apparently does with MTs and Magnis. But, my more basic point is that, no matter what configuration you end up with, it is not proven stability safe until you test it for both STATIC and DYNAMIC stability. These flight tests are simple and safe, and they will easily identify the safe stability (airspeed/power) envelope within which that gyro should be limited.

Thanks, Greg

PS: Chuck, When I first decided to try to do something about all the unnecessary fatal accidents in gyros - back in the early '90s - you were my inspiration and knowledge source. You were a main reason I also focussed on and experimented with both CLT and LTL, and "T" tails with highly embedded HSs. It does pain me now to feel I need to take issues with some of these principles. But, my experiences since the '90s with the Magni, with training dozens of new pilots in the Magni (and, for a while training students to fly less stable gyros - frustrating!), and my involvement with many diverse perspectives and prejudices in our ASTM gyro work, has convinced me that we need to widen our view of just how to improve safety in gyros - beyond the purely STATIC analysis. And, beyond any admirable but impossible attempt to purely provide formulas and prescriptions to try to identify stability characteristics on paper. It's fun, but not practical! The better way is to do all you can on paper, but not depend on it. Depend on flight test results. The final proof of the pudding, IMHO, is the accident record which is hard to dispute and what our real goal is!

Pontificating does not make it so.

I don’t know why my friend is dead and neither do you.

There is no evidence suggesting that Terry was incapacitated.

Drag doesn’t magically work on the bottom things and not the top.

In my opinion the thrust line is not relevant if the engine is not producing thrust.

The witness did not report oscillations so it seems there was nothing to dampen.

Bill was not new to gyroplanes and had quite a few hours of instruction.

In my time with Terry as an instructor he was very conservative. He always tried to stay ahead of things.

In my opinion imagining that the low thrust line is the cause of the airspeed instability in a power off situation and condemning attempts to get the thrust line more aligned with the center of gravity because of your fantasy about the Magni is irresponsible.

In my opinion to say it was preventable by design when you don’t know what there was to prevent and you don’t understand the design defines arrogance. I am not comfortable with simply allowing your statements to slip by unchallenged.

In my opinion making things up about my friend’s crash to support your unsupportable fantasies is a new low for you.

Thank you, Vance

[StanFoster]

Vance- I know Greg well enough that he is of much higher character to be making up stories. His point is the nature of Terrys gyro to continue increasing speed in a trimmed state...after the power is reduced. I am simply varifying that was true with Terrys SparrowHawk and also mine. After Terry and Bills accident...I went out and did Gregs stability tests, and was troubled by the speed stability test failing everytime...and I am not exaggerating in the slightest how the speed just keeps increasing till I chicken out.

I wish I had done a double hangtest on my own SparrowHawk to see how much the obvious LTL was. I would guess it was several inches by the way the nose falls abruptly with power loss. I always said the nose dropped in my SparrowHawk more than the nose in my RAF raised when the throttle was chopped. Of course its desirable to have the nose lower a little...but you would have to experience what I call excessive nosedown. The very hard backstick forces that I had to apply was one reason I kept making noise to GBA to get me that 5/16 rodend upgrade. I was told it was not needed , but for piece of mind I wanted it. I never had a gyro that had to have so much back stick forces to do turns etc.

I remember that first turn I tried in Terrys SparrowHawk during my first flight with him when I was trying to decide if I wanted one. My airspeed was going crazy and Terry pointed out to me to give it plenty of backstick. I knew that...but the first time I didnt realize how much it took.

Of course we probably will never know what happened to cause the wreck of Terry and Bill, but having loss of backstick.....along with the nature of this machine to keep accelerating as I can personally attest to....is just one "possible" scenario. ....and I dont feel anyone is stating this is what happened. But in my mind, it was definately possible.

Stan

Stan

[C. Beaty]

It would be informative to hear from someone flying RAF blades on their Sparrowhawk or RAF conversion.

[C. Beaty]

An airfoil moving through the air behaves similarly to a thin plate running midway between upper and lower surfaces. If curved in the shape of a venetian blind slat, it tends to twist nose down.

For use as a rotor, if not symmetrical, it must have an upswept trailing edge that behaves like an up elevator. Propellers and the like are short and stiff so can manage without TE reflex.

A rotor blade that tries to twist nose down does so to a greater extent on the advancing side of the rotor disc than on the retreating side because of the airspeed differential. This amounts to a sort of built in swash plate that tilts the rotor disc nose down. Excessive need for back stick force is a good indication of this.

This was the cause of airspeed runaway on the Cierva C-30 as described by Peter W. Brooks in my post a page or two back.

I’ve included a picture of 2 versions of a Clark Y. The Clark YH evidently was designed for helicopters whereas the standard Clark Y was not.

[StanFoster]

Chuck- Thanks for your inputs. As always....unbiased and just stuck to mathematics. I remember reading comments before from you about the possibility of why a rotor tends to have its own swashplate inputs as you described. This all makes sense and fits into what maybe explains why the airspeed kept increasing in my SparrowHawk. I loved the way it flew....dont get me wrong...I just had to get used to much heavier stick forces...and a strong tendency ...too strong in my opinion...for heading to the earth too steeply when the power was cut.

Stan

[Doug Riley]

The old NACA report about the full-scale wind tunnel test of a Cierva-Pitcairn rotor mentions something that sounds odd to us now.

The authors state that the PCA blades were purposely set up with a relatively aft CG. They state the reason for this to be to create a sort of mechanical reflex effect: The centrifugal effect "pulls" outward parallel to the tip-path plane. With the blades coned, this pull is actually slightly DOWN relative to the rotor blade. Thus, it tends to twist the blade nose-up, with a torque that increases as the square of RRPM.

Obviously, this mechanism can't respond to the difference in airspeed between the advancing and retreating blades (unlike reflex). It therefore can't accurately compensate for the tendency of the rotor disk to tuck at higher airspeeds in the absence of blade reflex.

By the same mechanism working in the other direction, an over-balanced, torsionally limber rotor might be subject to RRPM runaway even if it had some reflex.

[gyrogreg]

All you really need is a statement something like this..

If requested and appropriately substantiated, EASA can approve
Alternative Methods of Compliance

This was cut/paste from an EASA AD.



I could support this option in any prescriptive configuration mandate.

This also allows the prescriptive mandate to be conservative enough to fairly reliably assure safe handling and stability characertisitcs - such as a mandate requiring < 2" prop thrustline offset (under all allowable loading conditions), and at a large (how big?) airfoil HS with a moment arm to the CG of at least a 2 ft behind the prop (It may be better to specifiy this moment arm based on HS size, and MOI of the gyro - somehow.).

If a builder or designer can't meet the prescriptive mandate, then they have the option to demonstrate flight stability (under all speed, power and loading conditions.) Now the problem will be determining what these prescriptive configuration parameters should be for different size and weight and MOI and speed gyros.

Flight testing for this exemption does not need to be difficult, unsafe or expensive. This flight test is simple and quick. I suggest the ASTM standards criteria be applied as the requirement. Those flight tests will identify the power/airspeed/loading safe limits - which should be applied to that gyro - set the Vne. Expensive instrumentation is not really necessary - if it gets too expensive to do, small producers will not be able to afford it. It would be nice to have instrumented data to verify results, but it should be good enough just for the seller to provide a "Letter of Compliance" to the new owner - if they lied on that LOC, they would be at a huge liability risk anyway!

Thanks, Greg Gremminger

[GrantR]

I thought the cause of the SH accident was most likely due to the control stop limiter backing out and jamming the stick where they could not pull back.

How does a LTL exactly contribute to a gyro not passing the speed stability test? Is it because its trimmed with less disc angle to fly level under power so at trim setting it needs more aft trim to compensate for the loose of the prop pushing below the CG?

In a HTL It would be trimmed with more aft disc angle to compensate for the TL pushing above the CG so when power is chopped the nose goes up due to the need for less aft trim because the push is gone above the CG.

[gilgsn]

Just a thought, and I am no expert... Could a simple system be used to raise a small elevator on the HS when the stick is pulled all the way back and with enough force, thus creating more down-pressure on the tail?

I am thinking of this because a very large HS has a lot of drag. However, a smaller one with an elevator could create more down pressure when needed without the constant drag penalty...

Gil.

[gyrogreg]

Chuck,

I do have experience with this. I had an original version of Dragon Wings - the early ones without the trailing edge reflex - got them second hand from Carl S. I replaced the Skywheels on my stock, low seater Air Command. Very noticeable was the tendency to increase airspeed when airspeed deviated above the trimmed condition. If you let it go very far, required a lot of back stick to recover. (This also worked in reverse at airspeeds below trimmed condition).

However, I suggest this is different than what Stan is describing. In my experience with this, it did not matter whether I was applying power or not - it would always tend to runaway on airspeed when I pushed it beyond the trimmed airspeed. This was on a definitely HTL gyro - with the meager AC HS!

I believe Stan is describing this airspeed runaway condition only when power was reduced. That is the same as reported by Jerry Loeser, the other owner/pilot who first tested this condition. Maybe the tendency to runaway was countered, with power on, by the LTL nose-up moment the prop created - forcing the CG further forward of the RTV. But, I believe the tendency for runaway airspeed - static airspeed instability - was simply a characteristic of the LTL configuration - without the help of the nose-up LTL prop thrust, or prop wash enhancement for the embedded HS.

This is all fun to speculate as to technical mechanisms. But, what really counts is what the results are. It doesn't matter much if this runaway characteristic is from the rotor or from the LTL, if the gyro were tested to identify this condition and corrected - or at least identify the flight conditions (power, airspeed and loading) where it might present some jeopardy.

If corrections are required, then it would be important to try to identify what is causing the problem - rotor, prop thrustline, HS, etc. But, IMHO, the first thing I would try, if it were mine to try, would be a large airfoil HS on a long tail in the free air slipstream whre it does not depend on propwash for its effectiveness.

Thanks, Greg

[gyrogreg]

I thought the cause of the SH accident was most likely due to the control stop limiter backing out and jamming the stick where they could not pull back.

Grant, I'll take a stab at this. It is possible that the control stop had unscrewed enough to limit back stick. But, certainly it would not have continued to increase more forward stick once the pilot pulled the control back against that stop. The trimmed airspeed, the airspeed that an airspeed stable gyro should maintain, is determined by the stick position. So, if the stick position was at least held against the aft stop, the airspeed should not have increased above that trimmed airspeed - if it was airspeed stable.

But, if the pilot did hold the stick against that rear stop, for the LTL characteristic that I am supposing, a reduction in power would have caused the trimmed airsped to increase somewhat - but it should then be airspeed stable maintaining that new trimmed airspeed. In this accident, the witness pilot reported that it just kept nosing over, fster and faster - not a stable airspeed characteristic.

How does a LTL exactly contribute to a gyro not passing the speed stability test? Is it because its trimmed with less disc angle to fly level under power so at trim setting it needs more aft trim to compensate for the loose of the prop pushing below the CG?

In a HTL It would be trimmed with more aft disc angle to compensate for the TL pushing above the CG so when power is chopped the nose goes up due to the need for less aft trim because the push is gone above the CG.

I'm not sure I follow your reasoning, but I think you do have the right idea about the nose response with power changes for LTL or HTL. But maybe there is something more there someone else can comment on.

But, IMHO, an LTL gyro is not necessarily airspeed unstable just because it is LTL. In this airspeed runaway case, I believe that the airspeed instability was from the inabibility of the HS to balance the other aerodyamic airframe moments - when the HS effectiveness was not enhanced with propwash. Upon reduction of power, the LTL will naturally pitch a bit nose lower to re-balance the Sum of Static Moments on the airframe. This is a new, higher trimmed airspeed. But, in this case, the HS nose-up moment no longer balanced the increasing nose-down moments on the enclosure, windscreen LG, etc. IMHO, it is also possible that the airflow on the HS was disturbed, shaded, and reduced by the changing airflow patterns behind the enclosure - not able to statically balance the other increasing nose-down aerodynamic moments on the airframe.

This is not necessarily purely an LTL issue. An HTL can have similar results - at lower power settings if it has a similar HS situation. But, upon a reduction of power on an HTL, the nose rises and the airspeed slows down, so you would more likely be in the runaway airspeed in the slowing airspeed direction.

Of course, the whole situation could be compounded if you also had some of the rotor blade airspeed instability Chuck describes going on at the same time. All of these questions, again, suggest you need to do flight tests.

Thanks, Greg

[C. Beaty]

Someone must fly RAF blades on a Sparrowhawk or RAF CLT conversion.

The RAF blades I examined were ¼ chord balanced as well with a zero pitching moment coefficient.

[gyrogreg]

Pontificating does not make it so. Sometimes I just don’t think it is worth trying!
There is no evidence suggesting that Terry was incapacitated. Not my supposition, that is what the manufacturer suggested.
Drag doesn’t magically work on the bottom things and not the top. ? Your point?
In my opinion the thrust line is not relevant if the engine is not producing thrust. Ah, something we agree on. But, when the rest of the gyro is designed to accommodate the thrustline – such as long landing gear, dropped keel, that can be relevant.
The witness did not report oscillations so it seems there was nothing to dampen. Where have I suggest it oscillated? I did suggest that it had enough “pitch damping” to avoid an AOA instability buntover. The dynamic pitch damping just allowed the nose-over pitching to be slow, resulting in airspeed runaway, not a bunt. “Damping” does not necessarily relate to oscillations, it relates to any changing motion.
Bill was not new to gyroplanes and had quite a few hours of instruction. In my time with Terry as an instructor he was very conservative. He always tried to stay ahead of things. I agree that the pilot was very accomplished and would certainly not have allowed the gyro to slowly nose over into a dive into the ground – if he could have. Ruling out mechanical failure, that may be why the manufacturer suggested pilot incapacitation. But, even if there was a mechanical failure of the controls, an airspeed stable gyro should maintain at least some trimmed airspeed. The trim spring, if it broke, would cause nose-down action and stick forces, a much higher trimmed airspeed, and a rapid nose-pitch over, not slow. But, a broken trim spring should be – is supposed to be – readily handled by the pilot – unless incapacitated!
In my opinion imagining that the low thrust line is the cause of the airspeed instability in a power off situation and condemning attempts to get the thrust line more aligned with the center of gravity because of your fantasy about the Magni is irresponsible. What fantasy? (Oh, I see! Re-direct the issue and personalize it! That’s an Alinsky tactic, isn’t it?) Sometimes I just don’t think it is worth trying! I have not “condemned” CLT! I am pointing out that it is not an assured panacea and that almost everything is a compromise.
In my opinion to say it was preventable by design when you don’t know what there was to prevent and you don’t understand the design defines arrogance. I am not comfortable with simply allowing your statements to slip by unchallenged. Sometimes I just don’t think it is worth trying! We do have reported evidence that there is an issue with power off airspeed stability (or at least was, I’m not sure about the SH II.) If you want to challenge specific technical differences you have with what I have presented, present the objective technical reasoning behind your position - objectively and constructively. But, if you are going to get personal, I’m not continuing.
In my opinion making things up about my friend’s crash to support your unsupportable fantasies is a new low for you. Vance, sorry you are so bitter. I had a friend lost in that gyro too – I don’t think I’m bitter, I’m just passionate! I’m not making things up. I'm trying to discuss issues that might help save lives. I’m sure Terry and Bill would want us all to learn something from their accident – so their tragedy and the tragedy to their families would not be in vain! I was trying to be as considerate as I could – I never used their names until right now – trying to keep emotions from interfering with objective discussion. Thanks for the backup, Stan.


Conversation over - Greg

[GrantR]

Greg,

Disc angle was incorrect terminology on my part. With LTL I meant the thrust rotates the airframe around the CG nose up so to get the frame level you have to move the RTV behind the CG to fly level under power. The lift is acting behind the cg to get the nose level under power. When the thrust is reduced the nose pitches down because the trim is set to balance the gyro at a set power. So the trim is not in balance without the thrust rotating the airframe around the CG nose up. So in trim the RTV is still behind the CG making the gyro speed up with reduced power.

On an HTL it works the other way. In trim, the RTV is ahead of the CG thus pulling up the nose to compensate for the HTL rotating the frame down around the CG. In this case when the thrust is reduced the gyro slows down and noses up with a set trim.

A true CLT machine should not change pitch with power changes. I am sure its nearly impossible to have true CLT due to changes in fuel loading and pilot weights.

This is where a good H stab comes into place to compensate for these variations.

[Chuck Roberg]

We do have reported evidence that there is an issue with power off airspeed stability (or at least was, I’m not sure about the SH II.)

I have some time in the SH II as well as the SH I. I would say the SH II has the same tendency on reduction of power for the nose to drop and the A/S to increase.

I'm used to it so it so I automatically add back stick. But I have had a student or two not used to it and the A/S builds up pretty fast. If there is a point at which the A/S will stabilize. I don't know because I never let it go to far.

[gyrogreg]

Grant, I can't find anything wrong with your explanation. One point of clarification:
[QUOTE=GrantR;361719] With LTL I meant the thrust rotates the airframe around the CG nose up so to get the frame level you have to move the RTV behind the CG to fly level under power. The lift is acting behind the cg to get the nose level under power. /QUOTE]

The airframe automatically rotates to the point where all of the moments are balanced. (That's not necessarily when the gyro is "level". Level is determined how the designer decided to angle the keel to the rotor spindle - basically the hang angle.)

When you remove one of the moments, such as prop thrust, the frame must re-adjust it's pitch attitude to re-balance the remaining pitch moments on the airframe. The significant static pitch moments on the airframe are:
- Prop thrust - CG
- RTV-CG
- HS - CG
- And any number of individual aerodynamic drag and lift moments from the airframe: Wheels, sloping windscreen, tail, pilot's toes, etc.

-----------------------------------------More info:

"Trim" is simply set by the angle of the spindle axis, which maintains the rotor disk axis (RTV) starting point. (When you are moving forward, or any direction, the rotor disk adds in a bit more disk angle - "blowback" - when the rotor adjusts for dissymmetry of relative wind.) Wherever the trim spring, or the pilot, maintains the spindle position, that should set the "trimmed" AOA and airspeed - on an airspeed stable gyro. The pilot sets the trim then, or holds the stick in a position, to achieve whatever airspeed he/she wants it to fly at.

If you "fix" the stick, in one position, then change the power level, the reaction or change in trimmed airspeed is the easiest way to determine if the gyro is HTL, CLT, or LTL. If it is true CLT, fixed stick trimmed airspeed will not change. Of course, you would need to try this at various Fixed (trimmed) stick positions (airspeeds) to be sure it is still CLT at all airspeeds. It might be different because, for instance, at different airspeeds different air (than free airflow) might be on the HS. Then, you would also need to test it when the tank is empty - or fuller! Then you would need to check it with your much trimmer wife flying! That darn "CLT" is so illusive!

BTW: "Fixing the stick" is the quickest way to test static airspeed stability. Do this on a moderately turbulent day - afternoon thermals are good! If the gyro flies at, or returns when disturbed, to a steady airspeed, it IS Statically Airspeed stable. Of course, you need to try this at various combinations of power and airspeed and loading to see if there are any power/airspeed/loading limits beyond which the gyro no longer maintains a "trimmed" airspeed. That would be your Vne - if there is a limit.

BTW2: If you conduct the flight test above for static airspeed stability in turbulent air, and it doesn't scare you by "getting wild" when the stick is fixed, you have also just proven it is DYNAMICALLY stable - which also confirms it is AOA statically stable and resistant to both buntover (or PPO) and PIO. So, when you do the simple test above, test it at the various airspeeds by increasing airspeed in small increments (5 mph) until you reach your Vne - or it "gets wild". If it gets wild, and you need to release the fixed stick and steady out the gyro yourself, you just identified the buntover limit - subtract 5 mph and that is your new Vne!

One caviot: You must physically "fix the stick" - mechanically, not just with your hand! The easiest way to do this is to use a small chain secured forward, and secured through an electrical clamp on the stick with the chain held tight under your hand on the joystick grip to keep it from pulling through the clamp hole. Hold the chain tight under your hand and pull the stick back to hold the chain tight - the stick is "fixed". If you need to take over control again, just loosen your hand and let the chain slip free. Shorten the chain to increase airspeed to new "trimmed" positions. With the chain pulled tight, it is still OK to apply roll inputs to keep the gyro level during your test runs - those roll control movements are not stabilizing inputs from the pilot.

If you do this test, and you should to identify your Vne or safe flight envelope, I would appreciate you sending me your results.

Thanks, Greg

[Heron]

Greg and Vance
The exchange gave me a funny feeling (not the good kind) I have lots of respect and love for both of you.
I was talking to Terry, minutes before he took off and we had agreement on exchanging flights SW/Golden, but he never returned. He was fumbling with his head and controls and I always think that I could have distracted him and something got neglected.
I also have problems with Greg´s long speech and it is not easy to follow his line.He knows a lot and defends his position and ship.
My only real problem is that we can´t get to the point, no as long as he is involved with Magni.
There is a point, we know that.
There will be always room for a Magni or other similar on the gyro realm.
I hope you guys get your heads together and keep the camaraderie.
Thanks
Heron

[StanFoster]

I cant begin to say how much I respect both Vance and Greg. I have to say that Greg makes a good point about speed stability that I had to chime in and put in my speed stability tests that I tried out. Vance tells what is on his mind..and I am just saying what is on my mind here. I feel Vance totally slapped Greg unnecessarily with a couple of statements. I know Vance well enough that he is very careful about typing what he really thinks..and to do it as PC as he can. I know Greg well enough that he isnt making stuff up, and he lost a couple of dear friends as well.

I want to see both my friends on the same side again. I mean that in two ways....Vance and Greg......and I would also like to see my friends Bill and Terry on the same side one day again also.



Stan

[Doug Riley]

I had the same experience with students in my tandem Dominator as Chuck Roberg reports. I instructed them to crank in full aft trim as they closed the throttle for landing. Some of them got her up to 90-plus anyway! It never became difficult to slow down -- the controls stayed light, and slowing down required just a flick o' the wrist -- but this ballooned the ship and made hash out of the student's glide path.

I can't say that this scenario would have been so benign without flight-adjustable trim.

In general, it is nice if the aircraft neither speeds up nor slows down when power is reduced.

I do think that arguing over whether HTL or CLT or LTL is "better" or "safer" is beside the point if we are all talking as competent designers. It's rather like the blind men examining the elephant by feel. Whether the critter is like a rope, or a snake, or a tree trunk depends on which end of it you grab.

We can plunk the (steady-state*) location of the rotor thrustline anywhere we want, whether the frame is HTL, LTL or CLT, by adjusting the placement, size and incidence of the H-stab. It is perfectly possible to have a down-loaded H-stab in a CLT or even LTL gyro. Just crank in the incidence and put the stab in the propwash. The rotor thrustline will simply be shoved aft of CG even farther than the engine thrust has already shoved it.

Whether we WANT the rotor thrustline way aft of CG is the more interesting question. Jean Fourcade taught us that it's good to have it aft. Fine. It doesn't have to be FAR aft, and, in fact, the farther aft it is, the larger the movements of the nose with either throttle changes or changes in rotor AOA. Setting up a heavy down-load on the H-stab FOR ITS OWN SAKE (say, by deliberately building in HTL) is even more beside the point.

In fact, I think it was Udi Zeigerson who pointed out that you don't REALLY need the rotor thrustline aft of CG by any minimum amount to achieve AOA/airspeed stability if you have a proper H-stab. The H-stab's lift changes more than the rotor's does (percentage-wise) as the aircraft's overall AOA changes. Rotor blowback provides a degree of airspeed stability all by itself; the H-stab only adds to it. Therefore, even a neutrally placed rotor thrustline (right through CG) will still result in positive AOA/airspeed stability if the H-stab is designed correctly.

Big "if" -- but not too big if the designer is competent and has the integrity to keep working until he gets it right. We still probably need crude rules of thumb for those who have nothing but thumbs... which is most of us.
_________________
* Of course, when you move the stick fore/aft, you alter the position of the rotor thrustline relative to the CG until the frame catches up. You can have a momentary rotor thrustline position far forward of CG without the aircraft being in any sense "bad" -- in fact, that's always where it is as you pull back to flare.

[All_In]

I do think that arguing over whether HTL or CLT or LTL is "better" or "safer" is beside the point if we are all talking as competent designers.

Very well said Doug, I’ve read enough of the old posts to know Greg was a major CLT advocate prior to getting his Magni. Then he flew and tested it and discovered that even with an HTL it was a stable aircraft. Since then he has been trying to discover why.
I beleive him and that the designers have made it a safe HTL machine.

It would be nice to have CLT IMHO, but....

[Doug Riley]

A lot of the participants in this section of the thread -- Grag, Vance, Heron, Stan, Chuck Beaty and I -- were there at that Bensen Days when Terry and Bill went down. Obviously, emotions run high.

[Jazzenjohn]

I have to agree with Vance. If you read Greg's posts, they have very little to do with the accident or why it happened. They have much more to do with defending the HTL gyro's he happens to sell and much lauding of Magni's. He put forward a highly questionable idea about wheel drag which purports that CLT and LTL gyros have a built in flaw, and several anecdotal theories that seem much more to do with bolstering a preconceived notion than rigorous determination of truth.

To Greg's credit he admits to the possibility of massaging facts to fit his prejudices etc. I agree with Vance that it went too far.

[JEFF TIPTON]

I thought the M-16 was HTL.

[gyrogreg]

I have to agree with Vance. If you read Greg's posts, they have very little to do with the accident or why it happened. ---------------------
He put forward a highly questionable idea about wheel drag which purports that CLT and LTL gyros have a built in flaw, and several anecdotal theories that seem much more to do with bolstering a preconceived notion than rigorous determination of truth. ------------

I thought I WAS addressing the question of this thread - what was the cause of this accident. When I joined this thread it had already determined that the accident gyro was "HTL" and that was the cause of the accident. The thread was also pushing for mandating prop thrustline. Since then, it appears this gyro was determined to be fairly CLT. I doubt that, that determination is too complicated to determine just from some hanging/balance measurements. But, if the conclusion is that this was CLT, then does the conclusion that HTL was the cause make sense? I'm offering other considerations.

But, first, I have been making the basic point, the only way to determine if a gyro is statically HTL, CLT or LTL, is to flight test it. That is easy - "fix" the stick in pitch, mechanically, then change the power to see what the "trimmed" airspeed does. If a power reduction causes the trimmed airspeed (at that fixed stick position) to slow down - that is HTL. If a power reduction causes the trimmed airspeed to speed up, it is LTL.

This needs to be tested at the various combinations of airpseed and power (and loading). There may be conditions where it actually can change from one static prop thrustline to another:

Why, because, as Doug R. said, the HS, and other things affected by airspeed, may change the effect of the prop thrustline - and at the same time the static positioning of the RTV relative to the CG. These other things can include the disturbed airflow around the enclosure on the HS, the mounted AOI of the HS, the propwash immersion of the HS, a lot of rotor effects Chuck alludes to, the amount of fuel or weight of the pilot, and, yes, perhaps minimally, the landing gear drag. You don't know if any gyro is static HTL or CLT, or LTL until you flight test it. IMHO, ANY STATIC stability conclusions are questionable if you don't do this test. But, if the examples of Magni, ELA and MTs are to be taken seriously, even these static conclusions are somehow incomplete!

BTW, when you do "fix" the stick, and the gyro will not settle out at a steady state "trimmed" airspeed, but either keeps increasing or decreasing, you have already shown it is not Airspeed statically stable. (Try this test in a SH at idle power and see if you get the same result as others have - and probably Terry and Bill did!)


They have much more to do with defending the LTL gyro's he happens to sell and much lauding of Magni's.

John, I believe you did mean "HTL". Yes, the Magni M16 is statically HTL. That's just not from hanging and balancing, that's from the flight test above also. I don't mean to be defending the Magni, or making excuses for its HTL. I don't need to do that, the accident record speaks for itself. But, I do point out that maybe the example of a Magni, and ELA, and MT suggests something is wrong with the HTL static paradigm that the conclusions in this thread are were being based on.

The point I am trying to make is, that when you properly install a strong dynamic damper - HS - the gyro even HTL gyros, may still be statically and dynamically stable - does not have issues with PIO or PPO. That is evidenced by Dynamic stability flight tests. But, it should be more convincingly evidenced by many, many hours flown on such configurations worldwide for years. I do, arguably maintain this is because we have all, for a long time, ignored how the DYNAMIC characteristics of a gyro affect the PIO, PPO and buntover susceptibility - irregardless of static RTV/CG analysis. Fatal accident susceptibility is the root question of this thread! I'm only suggesting let's look at what works and see if we can learn from that.

My major point is that, if you want the final answer to the question of whether ANY gyro is susceptible or prone to PIO or buntover (or even "PPO"), is to flight test it. The reason I jumped into this thread at all was because I saw the incomplete static presumptions based on HTL only, about to be mandated by ASRA in OZ. I was only hoping to point out how such a reflexive mandate to "do something" based on the (IMHO) paradigm of CLT would be a big mistake for safety and advancement of the gyro sport in Australia.

I knew I was probably stepping into a snake pit, but I thought it might be worth it - for the land of OZ anyway! Now, I'm going to step out. If anyone wants more help on how to do these flight tests, private message me and I'll work with you, but I don't need to endure this abuse any more.

- Thanks, Greg :rapture:

[C. Beaty]

Greg G., this is simply untrue.

1. Firstly a low thrustline does not have to be balanced by the HS. The RTV can do all the balancing by getting behind the CG.

2. Even if the HS carries some small residual load, the resulting nose drop is very different from a HTL PPO. Unlike a PPO the pitch down is not divergent as the the pitch down moment reduces (not increases as in a PPO) as the nose dips .

Finally, I believe it was in Benson days 2004 Chuck Beaty and I where talking about the same scenario and Chuck got me a ride with Rusty Nance( i think) on a twin dominator and explicitly told Rusty (or who ever the instructor was) to show me the efffect of rapid reduction of power on LTL gyros. The response was a slow slight drop of the nose, nothing dramatic.

Based on the above I do not see a theoretical or practical justification for the neccesity for slight HTL or the dangers you mention with LTL gyros. Airspeed runaway is nearly always associated with rotor behavior.

Chopping the power on either a HTL or LTL machines produces what amounts to a trim change; the nose will rise or fall and the airspeed will stabilize at the new trim speed if the rotorblade airfoils don’t have a strong aerodynamic pitching moment.

[Timchick]

Now here is where I am going to raise some fur! I am passionate about this subject because a friend or ours in CH 35 was killed a few years ago in a “CLT” gyro. Although the apparent consensus is that the instructor/pilot in this gyro must have had a medical problem, IMHO, this gyro apparently had an Airspeed stability problem – it dived faster and faster, steeper and steeper into the ground. Unconscious pilot or not, limited stick travel or not, any aircraft should not have runaway airspeed. It should maintain the airspeed it is trimmed for! Static Airspeed instability is a form of Static AOA instability – susceptible to buntover. The runaway airspeed, Airspeed Static instability is a form of a buntover – just a buntover that is slowed in pitch by a fairly good dynamic damper – a fairly large HS! The Airspeed and AOA instability, IMHO, was the result of this “CLT” “band aid”, really being LTL. This gyro probably has an adequate dynamic damping HS to avoid buntover, but it was not enough to avoid airspeed runaway! This gyro does have a BIG HS, but it is shaded behind the large enclosure and, IMHO, looses significant ability to counter the LTL moments when power is reduced. Pilots report that this gyro, with power reduction, lowers its nose and builds airspeed – and once over about 80 mph is difficult to recover with cyclic stick only. That this gyro was LTL has been confirmed by three pilots experienced in this particular model gyro – if you want more information on this, ask Stan Foster. Sorry, I may be a bit bitter about losing this friend! It didn’t have to happen, but I might harbor a little resentment that the ultimate cause was trusting “CLT” more than a good HS!



So if the back stop bolt backed out and limited how far back Terry could move his cyclic and the gyro had been Airspeed stable and only dove into the ground at 60 mph they would've survived? To me it doesn't matter if it hit at 60 mph or 90 mph. I believe the outcome would be the same.

[Arnie Madsen]

A sheet of plywood turned broadside to the wind has 285 lb of drag at 60 mph. If its center was attached to the mast 12” below the CG, perhaps we could have a dragover.

Until then, we'll just have to be content with ordinary PPOs.

Every once in a while something is explained that even I can understand. Thanks Chuck.

Today I have a much better understanding of Rotor Drag vs Fuselage Drag in forward flight. Simple explanations from brilliant minds are appreciated.

Arnie

[PW_Plack]

...it appears this gyro was determined to be fairly CLT. I doubt that, that determination is too complicated to determine just from some hanging/balance measurements...the only way to determine if a gyro is statically HTL, CLT or LTL, is to flight test it...

Greg, I only want to pop in to observe, as a person who makes a living with words, that your effort to make these terms cover more than thrustline/CG relationship confuses, and does not serve your argument. LTL/HTL can be determined with a dual hang test. A sloping windshield or low, draggy landing gear change static moments, but they don't change the thrustline.

If anything, we should be able to make certain assumptions about expected flight behavior based on thrustline offset, and the extent to which the machine deviates from this behavior, adjusted for known changes in the rotor's induced drag at various airspeeds, could be used to calculate the complex drag forces everyone says are beyond our ability to measure as small-time experimenters.

[bosca]

Hi All.
I'll ask this question the second time,however in a differant way.
Would a rotor that is heavier and or have tip weights or is more ridged be less prone to PIO,bunt etc with all other things being equal.
Kym.

[Jazzenjohn]

I thought I WAS addressing the question of this thread - what was the cause of this accident. When I joined this thread it had already determined that the accident gyro was "HTL" and that was the cause of the accident. The thread was also pushing for mandating prop thrustline. Since then, it appears this gyro was determined to be fairly CLT. I doubt that, that determination is too complicated to determine just from some hanging/balance measurements. But, if the conclusion is that this was CLT, then does the conclusion that HTL was the cause make sense? I'm offering other considerations.

There are always people that will call for a seemingly simple fix for a seemingly simple problem. It would be difficult to deny it wouldn't slow or stop buntovers. It would throw out the baby with the bathwater with respect to some safe HTL gyros. The Magni being one of them. Let me try and restate your position, correct me if I'm wrong.

A gyro that is CLT or LTL static, on the ground, is an indication that it will have a higher potential for safe flying characteristics than a very HTL gyro, dynamically, how it flies in the air, is more important.

A gyro that was 4" LTL but had a horizontal stab that was 10 degrees nose up might be "safe" statically, but nail the power while flying 2 feet above the runway might be fatal.

A gyro that is 2" HTL that has a 10 sq ft horizontal stab at 5 degrees nose down is technically and statically HTL. If you managed to fly it and rolled on the power, it would not behave as a HTL gyro, the nose would rise dramatically as if it were LTL.

Your position is that it is more important how it flies that how it measures on the ground. You believe flight testing is the answer.

But, first, I have been making the basic point, the only way to determine if a gyro is statically HTL, CLT or LTL, is to flight test it. That is easy - "fix" the stick in pitch, mechanically, then change the power to see what the "trimmed" airspeed does. If a power reduction causes the trimmed airspeed (at that fixed stick position) to slow down - that is HTL. If a power reduction causes the trimmed airspeed to speed up, it is LTL.

This needs to be tested at the various combinations of airpseed and power (and loading). There may be conditions where it actually can change from one static prop thrustline to another:

I think you mean dynamically, or at least it is far easier to think of it that way. Does a gyro behave LTL, CLT, or, HTL.

By the way, IMHO, the answer to the original question in this thread is - lack of adequate HS, and the lack of appreciation the pilot probably had in limits without a good HS. Who’s fault is that - probably not the pilot's!

This was from post 149 which was the first post where I thought you made a direct comment on the accident. I'm pointing that out because, as it often happens, a concept on the forefront of your thought might not actually make it into the text of your comments. Re-read your posts and see if that may be true in this case.

The point I am trying to make is, that when you properly install a strong dynamic damper - HS - the gyro even HTL gyros, may still be statically and dynamically stable - does not have issues with PIO or PPO. That is evidenced by Dynamic stability flight tests. But, it should be more convincingly evidenced by many, many hours flown on such configurations worldwide for years. I do, arguably maintain this is because we have all, for a long time, ignored how the DYNAMIC characteristics of a gyro affect the PIO, PPO and buntover susceptibility - irregardless of static RTV/CG analysis. Fatal accident susceptibility is the root question of this thread! I'm only suggesting let's look at what works and see if we can learn from that.

I agree completely, and I'm sure others do also. I believe we should go further with very general recommendations for horizontal stab area depending on thrustline offset, angle of incedense, aerodynamic shape, distance from prop, in or out of propwash, etc. and the possibility of verifying effectiveness through simple flight tests.

[Heron]

Mr. Gremminger
You are a respected member in the gyro community and in this Forum.
We have read you ad nauseam and still do, we try to learn and understand your position regarding the issue at hand.
The overwelming majority treats you with respect and I know Vance does it to. I only don´t know what was going on in Vance´s heart at that moment but, I don´t think you are being abused and would like to ask your continuance on the subject . . .
I think it could save lives and that is way more important than ego massage.
REGULATIONS MANDATES
Gyros are not equal, every bracket needs a limitations rule.
Maybe a relation rotorCg/frameCg should be studied and regulated, it seems to me it is the circular movement of those Cgs that will cause a bunt (provoked) or PPO (unexpected)
Slap 300 hp on a Magni and lets see what it does! (sorry, nothing against Magni, they have an envelope though)
I think 10 years is enough time for us to create something Official, Authoritary and Limiting for gyro design and safety. Or the blah blah will go on forever . . .
thanks
Heron

[Jazzenjohn]

--------------------------------------------------------------------------------

Hi All.
I'll ask this question the second time,however in a differant way.
Would a rotor that is heavier and or have tip weights or is more ridged be less prone to PIO,bunt etc with all other things being equal.
Kym.

A heavier rotor would raise the vertical CG and tend to make the gyro more towards CLT if it were HTL, and more LTL if it were CLT or LTL. That would make it less prone to bunt. How much difference in blade weight are you talking about?

A good Horizontal stab would have far more influence on whether a gyro was susceptable to PIO than blades.

[C. Beaty]

Hi All.
I'll ask this question the second time,however in a differant way.
Would a rotor that is heavier and or have tip weights or is more ridged be less prone to PIO,bunt etc with all other things being equal.
Kym.The crucial roll played by the rotor in gyroplane handling and behavior is often overlooked.

1) A heavier rotor raises the overall CG.

2) Tip weights slow down the following rate of the rotor; the rotor disc follows the stick more slowly. A tip-weighted rotor also follows airframe tilt more slowly and thus resists tilt, supplying what is technically known as rate damping.

2) The pitching behavior of the rotor blade airfoil, the tendency of a blade to twist nose up or nose down, has a dramatic effect on response.

For example, Bensen wood blades had excess trailing edge reflex (the “ducktail”) that caused the blades to twist nose up, more so on the advancing side of the rotor disc than on the retreating side. This increased cyclic flapping and thus the “blowback” effect. As a consequence, the stick had to be moved forward and reached the forward stop at a little more than 60 mph. Bensen wood blades required little or no trim spring tension at 50 mph.

Rotor blades that twist nose down produce the opposite effect; cyclic flapping and the attendant “blowback” effect is reduced or suppressed entirely. That increases the need for trim spring pressure because the rotor thrust vector passes more rearward of the pitch pivot of an offset gimbal rotorhead. In severe instances, the stick moves rearward with an increase of airspeed.

3) Chordwise CG of the rotor blade airfoil is a critical parameter; tail heavy, a rotorblade is likely to flutter or at best, to be unstable. Roll out of a tight turn and such a rotor will produce a strong ballooning effect.

A nose heavy rotorblade can produce strong angle of attack stability.

[Vance]

I have been around accidental death a lot.

If the exact cause cannot be determined I feel it is important not to say that it was preventable and blame the design.

That makes the deceased seem stupid for choosing a bad design and places a tremendous burden on the designer as well as opening liability issues.

To blame a completely unrelated characteristic of the flight envelope for a death seems irresponsible to me.

In my opinion people read this and imagine it is a debate and justify poor design choices with what they perceive as uncertainty.

I made an unsuccessful effort to back the rhetoric down.

I always have a challenge when people attempt to mask their lack of understanding with technical terms and use unrelated phenomenon to prove a point.

I don’t know enough to have many strongly held opinions.

I would hope that the forum can help people understand gyroplanes and how they fly because I find that to be part of the fun.

I will be sad if Greg stops posting, I feel his experience has real value.

I apologize for my bad manners, I have no excuse and I have not changed my opinions with time.

Thank you, Vance

[Doug Riley]

Bosca, I'd add to what Chuck Beaty said about rate damping that a lower rotor RPM also adds rate damping. Lower rotor RPM has been a trend since the days of Bensen's 20-foot blades with low pitch, small chords and 400-plus RRPM just to fly a 475-pound machine straight and level.

Some people, even back in the Bensen era, would slow their little Bensen blades down a bit by using pitch settings higher than stock.

Bensen liked high RPM blades and only reluctantly released a 34" rotor hub to replace his 24" hub. Large rotor diameter also decreases RRPM.

The McCutchen blades that came into widespread use with the advent of the Air Command in the 80's had more diameter, much more weight and larger chord than Bensens. They therefore had lots more rotor damping.

A rotor that responds slowly to control inputs for any of these reasons produces a force that tends to return the airframe in its initial position when the frame tips for any reason -- as long as the rotor is producing thrust. This rotor-damping effect contributes to the aircraft's stability during positive-G flight. It doesn't help at all during zero-G flight. That's when an H-stab becomes particularly important.

[PW_Plack]

...I think 10 years is enough time for us to create something Official, Authoritary and Limiting for gyro design and safety. Or the blah blah will go on forever...

Or, we could stop debating this in a vacuum, and go out and just test the machines!

If the industry consensus stability standards produced through the ASTM process have been released to the public, and the process for measuring them is simple, why aren't we seeing actual data? I can only think of two possible answers...

(1) The tests are producing data that doesn't back up the years of debate, or...

(2) No manufacturer has a machine that meets the standard, except within an envelope so limited it would hurt marketing.

I could think of no greater contribution by PRA, once it gets its financial legs under it, than to test machines independently and publish the findings. I don't think anyone else is in a position to do it credibly, unless the kitmakers and would-be LSA-makers form a manufacturers association independent from PRA.

[All_In]

Or, we could stop debating this in a vacuum, and go out and just test the machines!

If the industry consensus stability standards produced through the ASTM standards have been released to the public, and the process for measuring them is simple, why aren't we seeing actual data? I can only think of two possible answers...

(1) The tests are producing data that doesn't back up the years of debate, or...

(2) No manufacturer has a machine that meets the standard, except within an envelope so limited it would hurt marketing.

I could think of no greater contribution by PRA, once it gets its financial legs under it, than to test machines independently and publish the findings. I don't think anyone else is in a position to do it credibly, unless the kitmakers and would-be LSA-makers form a manufacturers association independent from PRA.
Yaw Mon! That is what Greg has been asking all of us to do for a couple of years now.

In addition Tim O (IIRC) had suggested setting up a company to do testing however, PRA would be perfect for this mission.

[Jazzenjohn]

I wonder if gyro testing should develop from the ground up. By that I mean directed testing by someone like Chuck B where it targets specific questions about specific models of Gyros by people willing to do the tests themselves. It seems to me that it would be easier to get something like that started, and would show results more quickly. For instance, Stan mentioned how his SH would seem to increase speed beyond what he was comfortable with when he pulled power quickly. Chuck asked if anyone had flown a SH with RAF blades to see if the same thing happens with those blades. The result could prompt the next test until a conclusion is reached about what is happening and what, if anything, should be done. This all presumes Chuck and others are agreeable.

[MichaelBurton]

As I remember the tests for power stability call for the gyro to be at or near MPRS prior to doing the throttle reduction test. The SH falls within the requirements for power stability if done in this way by a hair. I have found that the RAF with the GBA mode also falls within the required criteria.

If the tail was not installed at a zero degree angle of incidence or if the engine is at an angle it may not pass this part of the stability testing. Undocumented mods like a prop change can also impact stability.

I believe that kit builders should have the tests performed on the completed machine and that the kit manufacture should take the lead in performing and reporting these test on the prototype. The test data should be included in the documentation of the kit. Critical areas that would influence the stability and corrective measures should also be provided.

Ultimately we the buyers are a force that can cause change. We need to be educated and demand those things that create a safe flying machine by buying only those machines with the data that supports safety.

This forum could go a long way in providing this education but we must be united and impartial in our critiques. We need to be slow to blame and sure of the evidence. Jumping to quick conclusions and pointing fingers will only cause division and cloud the issue.

[Doug Riley]

I suspect the kit makers are spending all their eneregy figuring out how to pay this month's light bill. The industry is in rough shape.

[Heron]

Paul Plack you are spot on!
Vance
WE love you too man, we all have weird moments.
Kit making
As people run out of time (precious commodity today) less kits will be procured, the trend will be RTF made from a kit. IN that path, the kit makers will have to train assemblers that can also double as distributors/sales force.
It is not easy to own a gyro, I compare this to the brazilian shore line, huge, beautyfull but empty of supporting structure, no marinas, no rescue, no mechanic, etc.
Basecaly you are on your own . . .
I am looking forward to the day that Mr. Gremminger comes to terms will al this stuff and like Paul Bruty did, join the choir.
The divisions created for LSA gyros is at least funny . . .use heavier boots and your gyro is a different animal, no clearance is given for a category.
I suspect that has a lot to do with the equation rotor/payload/power and a proper design for it.
thanks
Heron

[bpearson]

I suspect the kit makers are spending all their eneregy figuring out how to pay this month's light bill. The industry is in rough shape.

In the UK over the last few years 60 odd $90,000.00 factory built gyros have been sold. I suspect that a lot of them have been funded by home equity release (the economy over here has been living off this). It remains to be seen whether this will continue.

It means though that we cannot buy a set of plans and homebuild. So if you want to fly gyros you need to be rich. Other countries should be very wary of rushing to regulate or the same situation will arise. The penpushers who decide on such matters will seek out 'work' to pack out their intrays and look indespensible in tough economic times.

Of course we may get to a situation where the economy dictates that it cannot afford to regulate homebuilt recreational aircraft to the ridiculous extent it is over here and we can all go back to regulating our own safety!

[Dean_Dolph]

.... A safe range for Thrust line placement and a way to calculate its position while designing should be considered in any gyro design like weight and balance is considered in airplane design.....Agreed! An attempt should be made.I don't understand why people continue to build gyros with the seat a foot off the ground and the Thrust line aligned with the back of their heads!Grant, would you say that the GyroBee is an HTL machine? Most people who look at one say, yes!

The fact is that when Bee's have been had their CoM measured, they come in near center line thrust (NCLT = +/- 2") if not dead on CLT. While designing for CLT is a worthy goal it is also an unrealistic one..... In the drawing the seat on the CLT is only 3.5 feet off the ground and 2.5 higher than the HTL. A small change for a big improvement. This is with a 72" propSo, at this point I'll say I can't tell by looking at your drawings whether either machine is CLT.

Since these are mostly experimental machines that means there are many components with varying weights installed in various places that will be flown by pilots of varying weights and dress carrying a varying fuel load. This make achieving CLT under all conditions impossible. What we have to be satisfied with is that after our table top/computer design work that we end up with a NCLT machine that will pass flight testing without exhibiting any bad behavior.

The Boeings and Lockheeds of the world design their machines using the latest technology but they still flight test to prove the design. It isn't unusual for them to have to make tweaks, some major, in order to have a safe flying machine. Why do we think we can backyard design a machine that doesn't include flight testing as proof of design?

That last paragraph or two is only vaguely associated with your post and instead addresses other parts of this thread but I didn't want to make the effort to make multiple posts. Gettin' lazy in my ole age!

[C. Beaty]

In the UK over the last few years 60 odd $90,000.00 factory built gyros have been sold. I suspect that a lot of them have been funded by home equity release (the economy over here has been living off this). It remains to be seen whether this will continue.

It means though that we cannot buy a set of plans and homebuild. So if you want to fly gyros you need to be rich. Other countries should be very wary of rushing to regulate or the same situation will arise. The penpushers who decide on such matters will seek out 'work' to pack out their intrays and look indespensible in tough economic times.

Of course we may get to a situation where the economy dictates that it cannot afford to regulate homebuilt recreational aircraft to the ridiculous extent it is over here and we can all go back to regulating our own safety!Brian, the Australian Sport Rotorcraft Association is trying to reduce the fatality rate and preempt government intervention.
********
$90,000 for an aerial dirt bike is obscene.

[bpearson]

Brian, the Australian Sport Rotorcraft Association is trying to reduce the fatality rate and preempt government intervention.
********
$90,000 for an aerial dirt bike is obscene.

I'd rather live in a country where the government keeps the hell out of our lives Chuck but it's probably too much to ask these days!

It is a very grey area though when amateurs (I'm sure the ASRA know what they are on with but are essentially amateurs) start making the rules. When you have rules there is ultimately a blame somewhere. Then when it comes back to the government they then just ground everything.

Even our CAA have realised the only way to protect themselves is with a dereg class. No rules, standards, airworthiness etc....no comeback. If government want to save lives they would be better off regulating horse riding.

Don't expect anyone to agree! Even my wife finds my views strange.

[C. Beaty]

Even our CAA have realised the only way to protect themselves is with a dereg class. No rules, standards, airworthiness etc....no comeback. If government want to save lives they would be better off regulating horse riding.That sounds a lot like our ultralight class Brian; less than 254 lb., less than 5 gallons of fuel; no regulations, not even a drivers’ license. The theory being that you’re unlikely to kill someone else with such a machine. But not something that can be built with angle iron and water pipe.

Our present homebuilt/experimental class is primarily a dodge to get around airworthiness requirements; most are “factory” built and the “builder” sticks bolt A in hole B.

I’m all for minimal to no regulation if the machine is to be flown in sparsely populated areas.

[bpearson]

That sounds a lot like our ultralight class Brian; less than 254 lb., less than 5 gallons of fuel; no regulations, not even a drivers’ license. The theory being that you’re unlikely to kill someone else with such a machine. But not something that can be built with angle iron and water pipe.

Our present homebuilt/experimental class is primarily a dodge to get around airworthiness requirements; most are “factory” built and the “builder” sticks bolt A in hole B.

I’m all for minimal to no regulation if the machine is to be flown in sparsely populated areas.

Unfortunately Chuck they have excluded rotary wing craft.......they really did get burnt over the Air command saga!

We still have to be liscensed which I feel is reasonable....how would you know about regulated airspace etc, but they did a study into the risk of third party injury and came to the conclusion that it was negligable.

If we can build kit cars and modify motorcycles then drive them at 50mph 2 feet away from pedestrians then it is reasonable that we can fly homebuilts where the third party risk in a lot smaller.

I still maintain the view that prosecuting idiots flying around in homebuilt deathtraps will soon be fairly low down in our governments priorities when we will all be rioting on the streets because all the money has dried up.

[C. Beaty]

That AirCommand saga is proof of the gullibility of bureaucrats.

Red Smith, 3rd hand AirCommand owner and his “technical expert”, Bill Parsons along with someone I don’t know, met with the CAA, convinced them they were the leading experts and that all the AirCommand crashes were caused by the pump handle stick.

[GrantR]

Dean,

I think the Bee requires really heavy blades to make it to near CLT plus it uses a 40hp engine and a low disc loading to make it much more stable.

If your butt is up near the thrust line The gyro is going to be CLT or LTL as long as you don't have a lot of weight below. In the drawing I posted that would be the same airframe with a simple mod moving the seat up. Assuming this is a 5 gallon seat tank that is moving 30 pounds up.


OK so here goes. Imagine the gyro is hung up by the prop center line and the keel is aligned vertical.

Now lets say the weight of the rotor and other components above the thrust line is 60lbs. This weight 4.5 feet above the TL will result in 270 foot pounds at the TL. To have CLT you need 270 ft pounds on the other side.

Now the pilot of 200 pounds CG is 1.5 feet below the TL so 1.5X200 = 300 ftlbs below the TL.

Now the fuel is 30 Lbs X 2 foot below the TL = 60 Ftlbs below the TL

Now the landing gear and keel is 30 Lbs X 3.5 foot below the TL = 105 Ftlbs below the TL
So you have 270 pounds above the TL and 465 pounds below the TL.

That puts your vertical CG well below the thrustline as there is more weight below it than above it.


Now lets move the seat up 2 foot and see what happens.


We still have 270 foot pounds from the mass above the TL

Now the pilot of 200 pounds CG is .5 feet above the TL so .5X200 = 100 ftlbs above the TL.

Now the fuel is 30 Lbs X 0 foot = 0 Ftlbs of the TL

Now the landing gear and keel is 30 Lbs X 3.5 foot below the Tl = 105 Ftlbs below the TL

Add in 4.5 pounds for the seat riser with its CG at 2ft below the TL so 9 ftlbs


So you have 270 pounds plus 100 for pilot = 370 above the TL and 114 below the TL. This puts the VCG way below the TL.

However shifting the pilot and fuel down just one foot subtracts 100 ftlbs from the top side and adds 100 ftlbs for pilot below the TL and 30 ft pounds for the fuel.

So the result is 270 and 244 resulting in very close to CLT with slight LTL.

So small changes in pilot weight make large changes in CG location

[Heron]

So small changes in pilot weight make large changes in CG location
This is one of the things I am talkin about, gyros that behave differently (enough for a mishap) should not be allowed.
Heron

[EI-GYRO]

So small changes in pilot weight make large changes in CG location

I think you meant small changes in the vertical location of the pilot's weight make large changes in CG ?

Not as nit-picky as it seems.

[Dale Young]

unicycles are (typically) designed to be unicycles and those that buy unicycles know what behavior to expect from them.

what we are talking about here are not a kind of aircraft but a flaw in design.

A proper analogy would be banning unicycles that have a bomb embedded in the seat that goes off killing the user when they make a common mistake while riding the unicycle. A mistake that is dangerous but typically not always fatal when made in unicycles without the bomb.

Ppos are the result of a design flaw.

there are no desirable traits gained from having gyro susceptible to ppo.

.



bingo!!!!!

[bpearson]

bingo!!!!!

Ban them all.....lets save those people from themselves.

[StanFoster]

We should all stop any extra activities. When we get home from work, head for the closet and lock the door.

You know what? Death will still find you locked in the closet...as you will die from boredom.


Stan

[Heron]

Someone down in Ft Lauderdale, imported an albino mamba, the thing managed to escape and bit an innocent bystander at the back of a nearby motel . . .
Preventable?
Heron

[MichaelBurton]

Someone down in Ft Lauderdale, imported an albino mamba, the thing managed to escape and bit an innocent bystander at the back of a nearby motel . . .
Preventable?
Heron

Strange place to be bitten, I wonder if it hurt much?

[All_In]

I do not like laws that ban living life to the fullest.
I do not like the reputation experimental rotorcraft have because of folks without training becoming actual test pilots flying their own idea of what they THINK should be a safe design.

I believe we could live with the FAA requiring the flight-testing Greg G describes. If it passes you can register it, if not you need to fix it and try again.

[Vance]

I understand what you are saying John and would agree if I thought it would help.

I don’t feel that Greg’s tests address the causes of most gyroplane accidents that are stability related and I think there is a lot more to gyroplane stability than the tests uncover.

The tests are easy for anyone to perform so I feel we don’t need a rule requiring them.

I do not have tests in mind that are easy and safe that would uncover what I feel are the stability issues that lead to gyroplane deaths so I am not offering a solution, only an opinion that the tests that we have now are not the answer.

In my opinion part 23 has a lot more value as far as what to test and what results are desirable.

After a comprehensive design review and a lot of hanging I will have a test pilot test fly Mariah Gale before I fly her with my limited flight experience.

Thank you, Vance

[C. Beaty]

Vance, I’m coming to the belief that falling on your head in all those motorcycle crashes didn’t do as much damage as I had previously thought.

[Vance]

Thank you Chuck

Assuming I am not missing your sly wit that is a nice thing for you to say.

I see how fast these stability events take place and it is hard to imagine that airspeed stability is a salient issue.

Gyroplanes are very different than fixed wing aircraft and yet many of the same principles apply.

I struggle with over confidence as I build hours and it is not hard for me to see how someone would believe that an aircraft would always work, until it doesn’t and then it is too late.

Thank you, Vance

[All_In]

...

I don’t feel that Greg’s tests address the causes of most gyroplane accidents that are stability related and I think there is a lot more to gyroplane stability than the tests uncover.

The tests are easy for anyone to perform so I feel we don’t need a rule requiring them.

I do not have tests in mind that are easy and safe that would uncover what I feel are the stability issues that lead to gyroplane deaths so I am not offering a solution, only an opinion that the tests that we have now are not the answer.

In my opinion part 23 has a lot more value as far as what to test and what results are desirable.

Thank you, Vance
Well I know much less than you regarding rotorcraft.
I did not know that Greg's test would not uncover stability issues. :Cry:

I need to lean and research part 23 thank you, perhaps that is what I'm looking for.

Are there any tests that Chuck and the pros could offer us that would test for stability?

[Vance]

I did not know that Greg's test would not uncover stability issues. :Cry:



Hello John,

I am trying to be careful here so as not to offend, I did not say they would not uncover stability issues.

What I said was, “I don’t feel that Greg’s tests address the causes of most gyroplane accidents that are stability related and I think there is a lot more to gyroplane stability than the tests uncover."

I feel that his tests can identify specific issues but in my opinion they do not address the short period oscillations that seem to be at the heart of many of the stability related accidents.

I personally would not pronounce a gyroplane as safe just because it passed Greg's tests and I would not pronounce a gyroplane unsafe because it did not achieve that level of airspeed stability.

Thank you, Vance

[GrantR]

think you meant small changes in the vertical location of the pilot's weight make large changes in CG ?

Not as nit-picky as it seems.


Yes and no. If one pilot weights 150 pounds 3 inches below the TL that equals 450 foot pounds. If a 200 pound pilot sits 3 inches below the TL that is 600 foot pounds. So a 50 pound weight difference on the same seat give a 150 foot pound difference.

The closer the pilot weight is to the TL the less effect it will have on it the CG to TL alignment.

So in this case if the gyro is CLT with a 150 pound pilot and a 200 pound pliot flys the gyro, the gyro would need 33.3 pounds added to the rotor head to keep the VCG on the TL if the rotor head is 4.5 feet above the TL. Otherwise it will be HTL with the heavier pilot.

[splashdown]

Grant, you are confusing inches with feet.

150 pounds at 3 inches offset is 450 inch pounds, not foot pounds.

In your example there is a 150 inch pound delta between the two pilots. Presuming the first pilot had the aircraft balanced to start with, the additional weight required at the head (offset 54 inches) to correct for the heavier pilot would be 2.7 pounds.

[Bob Gregory]

So in this case if the gyro is CTL with a 150 pound pilot and a 200 pound pilot flys the gyro, the gyro would need 2.6315789 pounds added to the rotor head to keep the VCG on the TL if the rotor head is 4.5 feet above the TL. Otherwise it will be HTL with the heavier pilot.

I count seven places.
bg

Aeronautical engineering is highly educated guessing, worked out to five decimal places. PTAirco.

I see it now. I saw it before. I have seen it.
When it is loose it is loose. You could lose it.
When you lose it, it is lost. A loser does not mind losing.
A damper damps. To dampen makes it wet.
When it is taut, it is tight. If you are taught, you will learn.

[splashdown]

It was just an example Bob.
I was just trying to show the mistake re: inches and pounds.
I didn't think it warranted 8 decimal places (even though by your own admission aeronautical engineering only requires 5).

;-)

[Jazzenjohn]

The big differences from pilot weight would tend to occur more in Gyros that pilot or pilot/pax weight is a large percentage of the gyros AUW, which is true for most gyros.

The differences would also be more prevalent in gyros that have low seating positions whether or not they are offset with heavier rotorblades.

I would be interested in a thrustline test of a low rider Air Command gyro with a light pilot like Dave Seace and Skywheels, then checked again with Dragon Wings and a bigger pilot, say 220. I believe the thrustline offset would change by as much as 6 inches.

[Bob Gregory]

JJohn, I get 2.53 inches with Beaty's pusher. Measurements were from
photograph. So they are not inches, but units. Guessimates on weights.
Units translated to pilots 133 lb and 220 and blades 35 and 65 lbs.
Propeller to cg is 1.9 and 3.4 units. A unit is 0.6 inch.
Here is the sheet. You can make a second sheet and enter the heavy pilot.

[mceagle]

I have come into this conversation a bit late so please excuse me if what I say has already been covered.

I do not believe that a prescriptive design requirement, especially a radical one, is the way to go in the future. It could open up a very big can of worms. For the most part, the ASTM standards defined particular requirements, then left it up to the designer as to how they complied with those standards.

I do not intend to discuss the disadvantages of excessively high or low thrustlines, inadequate horizontal or yaw stabilization or poorly designed canopies, (all of which can contribute to a bunt over), but rather ways to overcome all these deficiencies in one foul swoop, without prescribing to what could possibly be restrictive to future design criterion.

Good safe performance and handling criterion and testing methodology has already been defined and reprinted not only many times on this forum but also elsewhere. If the aircraft manufacturers were compelled to comply with this criterion as a registration requirement then that would automatically exclude those with potentially fatal handling deficiencies. With annual registrations, dangerous gyros could be out of the system within 12 months.
Sounds too simple!

Of course the big problem would be the testing of gyros to meet this criterion. Private sales would be the main problem because registered manufacturers could not afford to make false statements. (they would most likely be caught out in their first sale with consequences for future registrations and sales). I guess private sales could be assessed by an instructor or someone else qualified to do so. Perhaps non-compliant gyros with a history of safe operation and an experienced pilot could be given a dispensation, as long as there were not sold on. Given the average service life of a gyroplane, they would eventually be out of the system anyway.
It may become necessary for the various Associations to purchase video and audio recording equipment to be used in test flights – a small cost considering.

There is also the problem of differing rotor brands, some with such markedly different performance characteristics as to change the whole handling of the gyro. I do not know how you would get around this one. Some pilots change their rotors as often as they change their underwear and it would be hard to assess the gyro with all the rotors that are likely to be installed.

However this rotor problem is one that would be encountered no matter how you tried to eliminate potentially dangerous gyros. Perhaps rotors also should have safe handling critera.

[Resasi]

From observation in a very short time of exposure to the gyro world, builders, pilots and machines are all incredibly individual.

In our present hanger with around 30 gyros, variations between even similar types can be large. Rotors, engines, controls, tires, fuel locations differ enormously even in the regulated environment we operate in. How much more so in other parts of the world with less or no regulation.

The Rotary Forum is an International repository, gathering place and dissemination point for safe practice. It is being acknowledged here at the moment, this is very much if participants take the time to read and learn on their own, and should perhaps knowledge of the correct way to build and operate these machines be required by greater regulation.

The PRA is rightly concerned about safety for all gyro operators no matter where they are. Could they perhaps organize a booklet that gathers and simply explains all major points of gyro safety that does not presently exist (with perhaps references to other works which contain greater detail), together with established guidelines and standards to be reached , and make it available at a reasonable price for the gyro community.

Yes the information is out there, yes there are books, but daily we have people come to the forum, asking very similar questions.

There appears even in the last two to three years acknowledgment of commonly held misconceptions, and a moving towards consensus on at least some issues that the early pioneers and designers understood well but perhaps many of their eager less educated and enlightened followers did not and have not.

This perhaps a step forward to more common areas of adherence to, and compliance of safe practice, without greater legislation that may stifle rather than promote the movement.
__________________

[Vance]

Hello Leigh,

I was about to recommend gyrowiki.com when I checked it and my computer is telling me that it, “cannot connect to the configuration database.” I have no idea what that means other than I am not able to get past it.

When last I looked it had all kinds of interesting explanations of how gyroplanes work.

Perhaps it is a temporary challenge.

Thank you, Vance

[Resasi]

Vance I suppose I count Gyrowikki along with the Forum although I shouldn't and yes it is a wonderful resource.

Sadly perhaps, more and more in our prepackaged instant gratification world, a handy little Pocket Bible that you don't have to connect to the internet and take hours of researching is, going to have quite a bit of appeal to many of those to whom this sport is a cheap quick way to get into the air.

[GraemeClarke]

Mceagle, the problem with your system is that it is very subjective. There are people who could fly a brick, and say it is stable.

[gyrogreg]

Checking for adequate stability, or more properly identifying the safe (airspeed / power) flight envelope, is not "subjective". It is mostly the standard fixed stick DYNAMIC stability flight test that has been performed on aircraft for probably 100 years now!

The British PFA and CAA have been using it to approve Section T certification of gyroplanes in the UK - even when they have very HTL. UK flight test pilots have used it to identify the probable causes of gyro PIO / buntover accidents in the UK - Dynamic instability!

Anyone can (should) perform at least the fixed stick Dynamic Stability test on their gyro - to identify the limits of the safe (airspeed / power) flight stability envelope - beyond which that gyro might be susceptible to PIO or buntovers.

Dynamic instability means that the natural phugoid (slow, long-period) airspeed oscillations do not self-damp. If, when flying with the stick mechanically "fixed" in moderate turbulence, the aircraft "gets wilder" (diverging) in pitch excursions that require the pilot to release the "fixed" stick and pilot-damp the oscillations, that aircraft is not dynamically stable and should not be flown beyond that airspeed at that power setting! Not a subjective test, and very eye-opening!

This is safe to do if:
- You are already comfortable in flying in that moderate turbulence so that you can pilot-damp any oscillations, AND
- You devise a way to quickly release the "fixed" stick when you need to start doing the flying again. (Small chain stretched tight and wrapped around the stick handle and securely with your hand.)

When the pilot is required to stabilize an aircraft, the aircraft will not self-stabilize itself, that aircraft is dangerous - at that airspeed / power combinations.

Professional test pilots have more specific ways they test the same thing:
- Test in calm air
- Input a disturbance with the stick - quick movement of the stick to start a phugoid oscillation
- Then immediately "fix" the stick to see if the gyro self-damps the phugoid oscillation.

But, the fixed stick moderate turbulence test does the same thing. Very objective, not subjective. Repeats every time!