Partially-Powered Rotor: Anti-PPO Device?

[C. Beaty]

Steve, I just looked up the gyroplane fatality rate for the years of 1970 through 1980 and for the most recent 10 years, 9/18/‘97-9/18/‘07.

In the 10 year period ‘70-‘80, there were 51 fatalities in gyros, most of which were Bensens.

In the most recent 10 year period, there were 36 fatalities, most of which were AirCommands and RAFs.

Off the top of my head, I’d say there were twice as many gyros flying in the earlier period than the later. If that guess is anywhere close to being correct, the fatality rate for the most recent period is 41% higher than the earlier period.

Now what was the difference between the two periods other than the design of the gyros?

There was no dual instruction in the 1970s. If someone wanted to
properly learn to fly a gyro, he had to take the Bensen training manual in hand and get towed behind a car, followed by crowhops, graduating to shallow “S” turns at a few feet of altitude. And it worked pretty well. Of the several hundred people in the Sunstate Rotor Club that learned to fly a gyro that way, not one got hurt other than a few scrapes from rollovers.

There were always those individuals, fixed wing pilots more often than not, that viewed the training method used by Bensen as dumb, jumped in a gyro and headed for pattern altitude with the old FW saw echoing in their head; “Airspeed and altitude is money in the bank.”

Why should dual instruction by a CFI make things worse?

 

[gwarwick]

I don't think KISS is incompatible with innovation

People have not used Composites but stuck to tube and weld because on a small scale the technology is not yet "garage friendlly". Plugs and molds are just too damn difficult particularly when trying to create complex curved shapes - ie ones with aerodynamic efficiency.

In the marine sector when Duflex became available the KISS crowd who swore by ply and wood (you can work it at home) suddenly adopted composite kit construction. (http://www.atlcomposites.com). My guess is when the technology matures sufficiently that carbon is as easy to work as chrome-molly the Gyro KISS crowd will sing its praises.

Similarly computer assisted stability is in it's infancy in affordable terms - Sourceforge has the first GPL Rotary autopilot software - but the author will tell you it crashes ! My guess again is when it works the KISS crowd will adopt it.

I'm a self confessed techno junkie - but I have a lot of time for KISS - when things get too complex without a long period to iron out bugs they tend to go wrong. The KISS approach often avoids this.

Having praised KISS, I would never the less love to have a cheap autopilot available to fly a gyro - it would be great if a truetrak type system could be implemented on a gyro for longer cross country trips. I suspect that the "pilot error" chorus in discussing PPO and Bunt overs has more than a grain of truth and when pilots are tired on long trips the odds get higher. Automated pitch stability on long trips might well save a life or two. Worth thinking about

 

[Mayfield]

In the 10 year period ‘70-‘80, there were 51 fatalities in gyros, most of which were Bensens.

In the most recent 10 year period, there were 36 fatalities, most of which were AirCommands and RAFs.

Off the top of my head, I’d say there were twice as many gyros flying in the earlier period than the later. If that guess is anywhere close to being correct, the fatality rate for the most recent period is 41% higher than the earlier period.

Now what was the difference between the two periods other than the design of the gyros?

Great observations Chuck.

Why should dual instruction by a CFI make things worse?

Is it the dual instruction that made it worse or, I hesitate to use the word, evolution of gyros that made it worse?

I "learned" to fly gyros using the Bensen method and my old MAC powered gyro. Other than minor incidents and one crash caused by my stupidity, the method worked.

Later, I flew gyros with HTL and huge amounts of HP. I'm not at all sure I could have safely self trained if those later aircraft had been my first experience.

Jim

 

[C. Beaty]

Certainly, Jim, the inbreeding contributed to the degeneration of gyroplane stability.

And don’t misunderstand me; I’m not arguing against competent instruction.

Steve, I don’t mean to imply you’re not competent but telling your students that everything is the fault of the pilot is very unhelpful. That tends to maintain the status quo and leads them to believe there’s no difference between one gyro and the next.

Teaching people to fly experimental gyroplanes is a whole lot different than teaching high school students to drive a car. The driver ed. instructor need know nothing about what’s inside an automatic transmission.

Automobiles are so designed and regulated that it’s unnecessary to know anything about how the machinery works.

There is no regulation of experimental gyroplanes so the pilot must know something of how they work.

I was recently reading through the FAA certification process of the Avian gyroplane (some of the Canadian process had to be repeated for the FAA) and it’s abundantly clear that they have no idea of how gyroplanes work either.

 

[trikesterkyote]

If you don't have the desire, will, or vision to attempt to advance that which is, then don't even attempt it. In fact don't even waste your time thinking about it. But if you are the kind of person who wants to try new things, has the vision and the resources to try to make it happen, then don't even think about NOT attempting to do it. Gyro evolution has been stunted for over 50 years and nobody has any idea what may have been if that had not happened. At the same time a lot of other technologies have come into being that may be applicable to the development of these aircraft that have never been accessible before. This is a win-win situation for the experimenter of today. There are few limits in such an environment for the foreseeable future. Adding a 48 volt, 15 hp max, 8 hp continuous "hub" style motor to an aerodynamically powered rotor system opens huge possibilities for design evolution and safety. The equations shift in favor of expanded speed, range, and economy with relatively few penalties in that the technology and hardware are all here now. There is the Inova Firebird leading the way in rocket powered rotor technology, The DeGraw Gyrhino, and a whole lot of other craft expressing the direction we are heading. These things didn't just happen by sitting around waiting for GM to build them. Go for it!!! Make it happen!!!

 

[murmur]

Thanks for your responses, everybody. I do remember reading that earlier thread, now, Mirek. Thanks.

It sounds like there are a couple of gotchas that would need to be addressed in a rotor-speed-lower-limiting mechanism. There's the yaw-torque issue at low airspeed (or at least at low thrust AND low airspeed, if the rudder is always in the prop slipstream).

There's also the failure mode wherein the rotor becomes unpowered at exactly the wrong time. You could say you're then left with the other mechanisms in place to prevent a PPO, but having power to the rotor in normal operation might tempt you to spend more time in situations in which there is more risk of PPO with the given thrust-line and HS configuration.

If the passive means can give you demonstrably greater reliability, those are the ones you'd use. The problem is the demonstrating. It seems far too dangerous to try to prove a given gyro configuration does NOT have a PPO mode.

 

[birdy]

PPO and PIO problems will stay with us until all the CFI are able to understand the causes.
Smartest thing youv posted ina long time CB.

It seems to me that a PP rotor would reduce the negative G bunting because the pp rotor wouldn’t slow down and dump air.
Only very slightly John.
The only reason why heli's dont PPO is coz they dont have a HHTL [ high horisontal thrust line]. If they did, they would if they went neg.

The question was ; Partially-Powered Rotor: Anti-PPO Device?
IOW [ to my inglish at least] would a PPR stop PPO.
Answer, no.

 

[quadrirotor]

A rotor of RAF2000, turning at 350 RPM, at zero airspeed:
-gives around 450 lbs of lift...
-need an PP of 30 hp!...

The craft will turn on the right, with gives you a noze-up attitude, due to the precession of the prop (if yet is turning...).

Can we do anything with that?

 

[Steve McGowan]

As Usual

As Usual

Certainly, Jim, the inbreeding contributed to the degeneration of gyroplane stability.

And don’t misunderstand me; I’m not arguing against competent instruction.

Steve, I don’t mean to imply you’re not competent but telling your students that everything is the fault of the pilot is very unhelpful. That tends to maintain the status quo and leads them to believe there’s no difference between one gyro and the next.

Teaching people to fly experimental gyroplanes is a whole lot different than teaching high school students to drive a car. The driver ed. instructor need know nothing about what’s inside an automatic transmission.

Automobiles are so designed and regulated that it’s unnecessary to know anything about how the machinery works.

There is no regulation of experimental gyroplanes so the pilot must know something of how they work.

I was recently reading through the FAA certification process of the Avian gyroplane (some of the Canadian process had to be repeated for the FAA) and it’s abundantly clear that they have no idea of how gyroplanes work either.

The numbers will dictate the Negative in gyro's...

How many people die in hospitals each year from wrongful distribution of meds.

But how many hours of Positive Flight Time can you possibly say were flown.!

And as far as the student knowing how the gyro works and what the parts do..

It's the instructors duty to fill ALL the blanks of the PRACTICAL STANDARDS. I have to live with every student's safety I teach, when it comes to gyro's. Not just NOW,, But from NOW ON !

ANY instructor that doesn't teach the fundamentals of the equipment,

Has No right being an instructor....

Ya know Chuck...... why don't we do as Britian did with Hand Gun's....

Confiscate all the gyro's that doesn't suite a particular design,,
and Crush the Damned things....

Would that make you feel better about it...???

 

[Resasi]

On todays BBC news. Gun crime in Britain now at an all time high.

 

[bpearson]

On todays BBC news. Gun crime in Britain now at an all time high.

Would put money on gyro crime in the form of illeagal flying is also up. Banning stuff normally drives it underground. Then you get no instruction, inspection etc.

 

[C. Beaty]

Steve, the number of people who die of lung cancer each year has no relevance to the number of people killed in gyros. If you like big numbers, 40,000 die each year in automobile crashes but in terms of fatalities per million miles, it is still the safest form of transport.

You and some of your fellow instructors need to clearly understand that while a pilot may be able, with a bit of luck, to keep an unstable gyro right-side-up, training does not solve the problem. Training only sweeps the problem under the rug.

No one has ever bunted a Dominator because it is impossible. Jam the stick against the forward stop and it will enter a steep dive but as airspeed increases, the angle of the dive will decrease due to rotor flapping angle (blowback) until an equilibrium speed is reached. That equilibrium speed will be the same as you’d get in level flight if you had enough power for the stick to reach the forward stop. Any power increase beyond that will not increase airspeed, the machine will simply climb.

Flap limited top speed is something I’ve experienced many times. Crank Bensen blades as high in pitch as the adjustment blocks will allow and the top speed will be about 20 mph with the stick up against the forward stop. More power and it just climbs without going any faster.

Doug Riley has stated a number of times that of all the people he has given demo rides to in his Dominator, from young teenagers to blue haired grannies, not one has ever PIOed when handed the stick.

It is disingenuous to claim the pilot causes PPO or PIO. But the problem will remain as long as it is blamed on the pilot and not the gyro.

Those numbers I pulled up from the NTSB site are real numbers, not opinions. There has clearly been no decrease in the number of gyro fatalities with the advent of dual instruction and if my speculation is correct, just the opposite.

 

[JPHarrison]

Study the readily available technical papers on the Fairey Gyrodyne, also J.A.J Bennett's series of papers on rotary-wing aircraft in "Aircraft Engineering". Anyone with an engineering/mathematical background will be able to understand their contents without too much trouble.

The Gyrodyne used a partially powered rotor with auxiliary propulsion in most of its flight envelope. Bennett also discusses the stability features designed into the Gyrodyne, which like the other rotorcraft designs he contributed to (Cierva Autogiros, Fairey Rotodyne), did not suffer from stability problems.

 

[murmur]

I'll look those up, JP. Thanks.

 

[Steve McGowan]

OK Chuck

OK Chuck

Steve, the number of people who die of lung cancer each year has no relevance to the number of people killed in gyros. If you like big numbers, 40,000 die each year in automobile crashes but in terms of fatalities per million miles, it is still the safest form of transport.

You and some of your fellow instructors need to clearly understand that while a pilot may be able, with a bit of luck, to keep an unstable gyro right-side-up, training does not solve the problem. Training only sweeps the problem under the rug.

No one has ever bunted a Dominator because it is impossible. Jam the stick against the forward stop and it will enter a steep dive but as airspeed increases, the angle of the dive will decrease due to rotor flapping angle (blowback) until an equilibrium speed is reached. That equilibrium speed will be the same as you’d get in level flight if you had enough power for the stick to reach the forward stop. Any power increase beyond that will not increase airspeed, the machine will simply climb.

Flap limited top speed is something I’ve experienced many times. Crank Bensen blades as high in pitch as the adjustment blocks will allow and the top speed will be about 20 mph with the stick up against the forward stop. More power and it just climbs without going any faster.

Doug Riley has stated a number of times that of all the people he has given demo rides to in his Dominator, from young teenagers to blue haired grannies, not one has ever PIOed when handed the stick.

It is disingenuous to claim the pilot causes PPO or PIO. But the problem will remain as long as it is blamed on the pilot and not the gyro.

Those numbers I pulled up from the NTSB site are real numbers, not opinions. There has clearly been no decrease in the number of gyro fatalities with the advent of dual instruction and if my speculation is correct, just the opposite.

trying to make any kind of understandable sense of this is futile... How the hell did the gyro get started and into the air in the first place..

as someone said earlier.. Instruct the student on ALL the aspects of the machine and how things happen.

Ya really need to start instructing Chuck,, Cause I surely don't know what the hell I'm doing..

Between you and a few other "Painters of Death" the only thing that safe is a Dominator. and it'll bunt over too..

PLEASE............Explain Chuck how Steve Adler of Denver crashed in his Dominator

 

[GyroRon]

I am not going to get into this pissing match, but my understanding of Steve Adlers crash is the gyro he was flying was NOT a Dominator... It was a heavily modified Dominator type gyro, but not a Dominator. Seems to me that it would not be fair to put Steve Adlers machine in the same category as mine, just as it would not be fair to put a heavily modified RAF in the same category as a Stock RAF.

 

[MikeBoyette]

Steve's gyro was a cross between a Dominator and a Carlanator.

 

[C. Beaty]

Steve Adler’s gyro was a very low thrust line machine; the propeller thrust line being well below the CG. There is no way in the world it could have tumbled forward. Some have speculated it could have tumbled nose up in a low “G” situation but I have my doubts. Just as likely to have thrown a propeller blade or some other catastrophic mechanical failure.

But the propensity for bunting over is only part of the problem with HTL. Such machines are unstable vs. angle of attack because the CG is forced to trail the line of rotor thrust. You are in effect telling your students it’s OK to fly tail heavy aircraft; that defect can be overcome with training.

A FW CFI wouldn’t last very long if he told his students that but the
FAA hasn’t caught on yet that HTL makes a gyro tail heavy.

 

[Steve McGowan]

Wow

Wow

Thanks Mike,, I've never heard of that Whatever else gyro mod you spoke of....

Now we go to extremely tail heavy gyro's,, uh..Damn..I thought that was what the hang test was all about...I'm more than likely wrong.

Chuck I'm sure you can get the FAA straightened out and we'll crush all these dangerous gyro's.

Yall exsuce me for sounding rude as The Mad Man is,, but what the hell. I'm just upset cause I don't have 10K+ wortha post on this rag.

Rall Fly Safe Now...........Ya Hear

 

[C. Beaty]

Steve, the “hang test” in no way affects the relationship between rotor thrust line and CG as has been discussed many times on this and Norm’s old forum as well as in numerous articles in the PRA magazine.

I hate to get into this again for at least the hundredth time but when a gyro is hanging from a rope attached to the teeter bolt, the CG is always directly in line with the rope, no matter what the dangle angle. The dangle angle affects control centering and if there is a horizontal stab present, its angle of attack and in that way, indirectly the CG vs. rotor thrust line.

The in flight CG is affected by things that tend to swing the airframe relative to the rotor thrust line; it being fixed in space by flight parameters. If a rotor flies at a 10º angle of attack at a given airspeed, it will always fly at that same angle if there’s no change of air speed, air density and AUW. Whatever the dangle angle.

Things that rotate the airframe relative to the rotor thrust line and control the CG are: (1) horizontal stabilizer load; (2) aerodynamic drag of cabin or airframe if offset from the CG and (3) and line of propeller thrust if offset from the CG.

Now this is all pretty basic stuff that any gyroplane instructor ought to understand before gaining certification but the FAA certification process for gyro CFIs is a dismal failure. Mainly because the people in the FAA responsible for oversight don’t understand it either.

Until this gets sorted out and a proper CFI certification process is in place, there will never be much improvement in the abominable gyro safety record

When it came time for a new rotorcraft flight manual, the FAA tried to write it themselves. Some guy in Oklahoma City was assigned the task, a nice enough fellow but I doubt if he’d so much as seen a gyro. I helped him as much as I could with numerous phone conversations and prepared notes and he was catching on pretty fast but then it was dropped. I suppose he retired or was transferred but I never heard from him again. This was perhaps 20 years ago.

Finally, the FAA subcontracted the writing of a rotorcraft manual out to Jeppesen. The tech writer assigned to the job was a person named Dan Morey who, again, had never seen a gyro. Dan was very conscientious and contacted members of the gyroplane community to learn whatever he could. He was fortunate to have made contact with Bill Clem who lives in Denver, also the location of Jeppesen.

Bill practically camped in Dan’s office for a couple of weeks and supplied most of the technical material. There was a stipulation imposed by the FAA; don’t offend anyone or criticize anything.