Flapping warning device

Detecting the proximity of flapping stops, or comparing Speed/Rpm with a memorized table is possible, but too tardy to be useful.
Mike's device will be able to anticipate sufficiently.
 
A question I have for Jean-Claude. Is it fair to say that a RRPM that is continuing to increase during a takeoff run is very unlikely to result in a blade flap situation, and conversely a decreasing RRPM, if it were to persist is likely to result in a flap situation?
The sequence as I understand it with regard to RRPM during takeoff is usually as follows:
1: Prerotate with stick forward either at standstill or moving slowly forward to a predetermined RRPM (say 160 RRPM) which is adequate maintain adequate blade stiffness to prevent chopping the tail in some aircraft like the MTO, and high enough to provide a buffer for the immediate RRPM decrease that occurs when the stick is brought back in the next step.
2: Gently bring the stick back as one applies throttle and accelerates. The immediate result is a decrease in RRPM which then begins to build again as the aircraft accelerates.
3: The RRPM increases in synch with aircraft acceleration until adequate RRPM and lift are achieved.
Which brings me to my question: If a pilot where to monitor quite simply the initial RRPM before bringing the stick back, and then subsequently monitor and ensure continued RRPM increase until liftoff, will he then be quite certain to avoid a blade flap situation.
My thoughts are that monitoring this RRPM acceleration either directly or with the help of the device described earlier, would be a more reliable way to prevent blade flap than a stop warning which would warn of an incipient flap situation which may well be too late.
 
IMHO
Proper training and specifically learning blade management is what is needed.
I have a rotor tack on my dominator, I will glance at it and confirm my visual observation of guestimated rotor rpm when pre-rotating. All the ole school guys (Bensen, Brock, Air Command, Gyro Bee, Dominator, etc.) learned to observe the rotor and know the signs of rotor rpm. Once off the forward stop as the rotor was tilted back, if too much air was passing through the disk. The rotor flapping would give you a little bump. Then a slightly harder bump. The next bump will push the stick into a sideways movement and back to neutral. The next one will be even more pronounced. Instantly push the stick full forward and power to idle; to arrest the rotor flapping to the control limits.
If the Pilot is being distracted by radio communication and reading instruments like engine rpm and rotor rpm and any other array of distractions; adding a buzzer/blinking light/gizmo will only add to further distract the Pilot from what he really should be paying attention to. If he/she is counting on a device to warn them of the impending rotor flap; it will most likely be too late to salvage the situation. The time lag for him to recognize the warning and react to it will only allow more time for the flap to progress.
That is one of the items with the Euro style machines that can and does create a problem. Also the Pilots are just operating by the numbers; and never learn blade management skills to be able to recognize what is happening.
 
IMHO
Proper training and specifically learning blade management is what is needed.
I have a rotor tack on my dominator, I will glance at it and confirm my visual observation of guestimated rotor rpm when pre-rotating. All the ole school guys (Bensen, Brock, Air Command, Gyro Bee, Dominator, etc.) learned to observe the rotor and know the signs of rotor rpm. Once off the forward stop as the rotor was tilted back, if too much air was passing through the disk. The rotor flapping would give you a little bump. Then a slightly harder bump. The next bump will push the stick into a sideways movement and back to neutral. The next one will be even more pronounced. Instantly push the stick full forward and power to idle; to arrest the rotor flapping to the control limits.
If the Pilot is being distracted by radio communication and reading instruments like engine rpm and rotor rpm and any other array of distractions; adding a buzzer/blinking light/gizmo will only add to further distract the Pilot from what he really should be paying attention to. If he/she is counting on a device to warn them of the impending rotor flap; it will most likely be too late to salvage the situation. The time lag for him to recognize the warning and react to it will only allow more time for the flap to progress.
That is one of the items with the Euro style machines that can and does create a problem. Also the Pilots are just operating by the numbers; and never learn blade management skills to be able to recognize what is happening.

That's all nice and good. Now how do you teach rotor management. Which grand wizard for a CFI should people use? Because its not like my customers went to a Euro CFI. In fact if they had gone to higher rotor RPM and then started to move only after reaching 170+ RRPM, in all 3 cases in our experience they would not have chopped the tail because they would not be outrunning the rotor by speeding up too fast.

I completely understand what you are saying but my field data says something different. I sincerely would like to understand then why that is. In the end data always outweighs theory no matter how good it sounds.
 
David,
Although all the airplane pilots are trained to avoid stall, none is asking for removal of the antistall warning.
Mike has written in the final comment of his post #1:
"I totally agree that the fundamental problem is training and competence in rotor management. But I think that we all have the right to make a mistake and hope that this device might save some pilots from paying for expensive repairs that could have been avoided."

Jeffrey,
Destructive flapping occur often most during RPM acceleration, even close to take-off rpm. Mike has record it by very progressive and cautious approaches.

The lack of centrifugal force of the blades is for nothing in the flapping.
 
This is an ongoing challenge for me as a CFI.

I had a client hit his tail without a tip over and when I called him after the mishap the first words out of his mouth were: “I did three things you told me not to do. I flew in winds that higher than I had flown in before, I let the tower rush me and I flew at a very busy airport where there is no place to land if things don’t work out. ” This man had flown and trained with two other CFIs that I have the greatest respect for and was a Private Pilot, Rotorcraft-Gyroplane pilot. He is also a 20,000 plus hour airline transport pilot.

A Calidus tip over from sailing a rotor on a touch and go was trained by one of the most through, rigid flight instructor I know and held a Sport Pilot, Gyroplane rating.

I had another client that with 15 hours of dual instruction on the day I was going to sign him off for his proficiency check ride do a touch and go in The Predator, center the cyclic and open the throttle. I have no doubts that if I had not been there he would have accelerated faster than the rotor and hit the tail.

Gyropedia has some thoughts on this that may prove helpful.

My feeling is that the American Ranger is one of the easiest gyroplane for pre rotation and takeoff out there.

I don't know if a warning gadget would be helpful.

I feel we have a desperate need to solve this mystery and come up with a solution.
 
How do you teach rotor management? Sorry, but did I really just read that?

I had the misfortune to drive a modern car on a recent trip. So much unnecessary junk on it, it was unbelievable. Little flashing lights to tell me when to change gear, irrelevant messages popping up on the screen where the dashboard used to be, little beepers and buzzers going off for god knows what reason, flashing arrows on the wing mirrors to warn me something was coming – and all totally pointless. Never mind the engine switching itself off when it felt like it! All any of it achieved was distraction from the most important priority of watching the darn road. The parallel with modern gyroplanes was unavoidable.

Teach people to fly the rotor blades without the junk – it really is that simple. They can always add the toys afterwards if they want, because they’ll know how to fly properly without them. Regardless of the occasional brain-fart, it’s beyond belief that in this supposedly enlightened age, people are apparently qualifying without the ability to recognise the onset of blade flap, or how to deal with it. It’s basic for crying out loud! They’ll be taking their family and friends along for joy rides with a huge piece of fundamental skill missing. How long before a passenger gets hurt? Yet we go along with it because a salesman decided to modernise training and old-school rotor handling isn’t trendy enough. Look where flying by numbers has got us. Sorry to get mad, but these stupid accidents make me bloody furious. We should be better than this by now.

Back in the sixties, Ken Wallis wrote ‘The practise of aerodynamic spin up [as opposed to using a mechanical pre-rotator] gives more “feel” for autorotational principle than a thousand words.’

Out of interest, how many new pilots would know how to fly without pre-rotator and tach (regardless if they can reach the blades or not), how many could actually put it into practice?

It’s too depressing to go through it all again (this topic resurfaces every few years, and Marion’s not here to share the burden anymore). Pick the bones out of this https://spinningonthewind.com/short-hops/ it’s all there – the hows and the whys – even how to do it with a factory-built.

There’s no mystery, Vance, honest. The solution is in the Bensen method where it’s been all along. It’s just not trendy, that’s all.
 
How do you teach rotor management? Sorry, but did I really just read that?

I had the misfortune to drive a modern car on a recent trip. So much unnecessary junk on it, it was unbelievable. Little flashing lights to tell me when to change gear, irrelevant messages popping up on the screen where the dashboard used to be, little beepers and buzzers going off for god knows what reason, flashing arrows on the wing mirrors to warn me something was coming – and all totally pointless. Never mind the engine switching itself off when it felt like it! All any of it achieved was distraction from the most important priority of watching the darn road. The parallel with modern gyroplanes was unavoidable.

Teach people to fly the rotor blades without the junk – it really is that simple. They can always add the toys afterwards if they want, because they’ll know how to fly properly without them. Regardless of the occasional brain-fart, it’s beyond belief that in this supposedly enlightened age, people are apparently qualifying without the ability to recognise the onset of blade flap, or how to deal with it. It’s basic for crying out loud! They’ll be taking their family and friends along for joy rides with a huge piece of fundamental skill missing. How long before a passenger gets hurt? Yet we go along with it because a salesman decided to modernise training and old-school rotor handling isn’t trendy enough. Look where flying by numbers has got us. Sorry to get mad, but these stupid accidents make me bloody furious. We should be better than this by now.

Back in the sixties, Ken Wallis wrote ‘The practise of aerodynamic spin up [as opposed to using a mechanical pre-rotator] gives more “feel” for autorotational principle than a thousand words.’

Out of interest, how many new pilots would know how to fly without pre-rotator and tach (regardless if they can reach the blades or not), how many could actually put it into practice?

It’s too depressing to go through it all again (this topic resurfaces every few years, and Marion’s not here to share the burden anymore). Pick the bones out of this https://spinningonthewind.com/short-hops/ it’s all there – the hows and the whys – even how to do it with a factory-built.

There’s no mystery, Vance, honest. The solution is in the Bensen method where it’s been all along. It’s just not trendy, that’s all.
Good Afternoon Shirley Jennings.

I have used the arm strong prerotator on The Predator once just to experience it.

Getting buckled in and plugged in was problematic with the rotor getting pretty slow before spooling back up.

The blades came up nicely and the takeoff roll was surprisingly short.

The Predator uses an electric starter for a pre-rotator that might see a hundred rpm in no wind conditions so my clients do have some experience getting the rotor up to speed with the wind.

What it is that I don’t know how to teach is: Follow the procedure.

People will do fine for a while and then they start short cutting the check lists and pushing the edges of the envelope.

These mishaps are so preventable it makes my head hurt.

As it is now most of my clients feel I spend too much time on rotor management.
 
Fara:
You see my point exactly, and I do not know how you can teach it either.
In the euro style machines. Pilots are taught/demonstrated to prespin to a certain number (example: 200 rrpm) then disengage the rotor and pull the stick to full rear position and apply full throttle and go. Once airborne, level off and gain airspeed and then initiate a climb at certain airspeed and away we go..
The problem I see with this, is if they are complacent or delay at applying throttle, the rotor can and may decrease rpm. Or if in a strong or gusting headwind the rotor may not be able to absorb the energy and be flapping into the teeter stops. The rotor is responding and flapping and compensating for dissymmetry of lift as it should, it is just that the flapping angle exceeds the designed control limits and that is what is initially felt in the control stick ( the lil bump).
There is nothing wrong with the way you launch a new Euro style machine; as long as everything goes correctly. Other than the Pilot may not understand the correlation between relative wind and angle of incidence to the disk and the rotor rpm and centripetal forces or coning angle in the blade and flapping to compensate for dissymmetry of lift.
In the Old school/Classic style machines you could hand start and nurse them up to about 70'ish rpm and then (each machine and rotor manufacture was slightly different) pull the stick back and start working slowly to gain rrpm. As the RRPM increased you could add a little throttle and increase the relative wind/taxi speed. Once above a certain number you could apply full throttle. It is basically the same, other than the pilot learned to visually recognize rotor rpm. This skill is lost in the newer style machines.
I have never heard it talked about, but you could get into an inflight blade flap condition that progressed to the point where the retreating blade impacts the rudder. It has very rarely happened and is never discussed. It is however discussed as we are discussing it here; in the takeoff/getting airborne in a gyro setting.
Once again, I don't know how you can teach it in the newer machines with the procedures you have to launch.
And it does not matter, in a few years nature will overtake us Ole Schools farts anyway. The classics will only be talked about and viewed in the museums and photographs.
 
Teeter stops for the teeter stops?

I guess you could position little spring-loaded plungers poking through holes in the teeter stops, with an electronic sensor to detect plunger movement, and use it to fire a warning light if things got too close.

We could program a PIC to compare airspeed and rotor RPM through a lookup table, and trigger a warning if the ratio between the two values got out of whack.
Paul, I guess I wasn't clear, but I was pointing out that we have such a device on every gyro already.
 
"1: Prerotate with stick forward either at standstill or moving slowly forward........"

Moving forward with the stick forward does nothing. Just uses up runway.

If you see folks doing that, it is probably just a hangover from prerotating by hand, where you would advance very slowly with a very small amount of backstick to get the rotors 'over the hump' in calm conditions.
 
In the end data always outweighs theory no matter how good it sounds.

Interesting sentence.

Outweigh, perhaps, replace, no.

The problem is that they can't properly use the data because they don't have a proper grasp of the theory, within which the data makes sense. Data on its own is just numbers.
You can bypass the theory with POH numbers and procedures, and it mostly works if the pilot follows it.
We read about the results when they don't.

Your POH should produce results similar to the Magni, in theory(mine). Better than the other competition, anyway.

Rotor handling and rotor flap can be easily demonstrated on a static rig in a light breeze. Done it with a Bensen gyroglider tied down.
The problem is that it may be forgotten over time without practice. But it should produce a reflex action to push the stick forward.
 
Good Afternoon Shirley Jennings.

I have used the arm strong prerotator on The Predator once just to experience it.

The blades came up nicely and the takeoff roll was surprisingly short.

What it is that I don’t know how to teach is: Follow the procedure.

People will do fine for a while and then they start short cutting the check lists and pushing the edges of the envelope.

These mishaps are so preventable it makes my head hurt.

As it is now most of my clients feel I spend too much time on rotor management.

I share Shirley's cry of despair, and your hurting head.

Glad you tried the armstrong method, Vance. Fun, ain't it?

My feeling is that folks would be more likely to follow the POH if they understood the theory and got the opportunity to feel the 'kick' of a flapping rotor.

If your clients feel you spend too much time on rotor management, show them the accident reports.

Adding a warning device may be proceeding further down the same road in the wrong direction.

Be interesting to see if it works, though. I would love to be proved wrong.
 
"1: Prerotate with stick forward either at standstill or moving slowly forward........"

Moving forward with the stick forward does nothing. Just uses up runway.

If you see folks doing that, it is probably just a hangover from prerotating by hand, where you would advance very slowly with a very small amount of backstick to get the rotors 'over the hump' in calm conditions.

EL- “moving forward with the stick forward does nothing”— that is true only to a certain extent.
Moving forward at a fast speed before the rotors have a chance to come up ( say 80 rpm) will induce flap if you are moving fast enough
 
I am no expert and have been observing and absorbing information at a rapid pace over the last year.
I have a tremendous amount of respect for the guys who know and appreciate those who graciously allow my stupid inquiries without ridicule.
I have a hard time understanding why the Blade flap could be an issue at any time “AFTER” conning of the rotors has taken place.
In a word-
You would have to try to get them to flap.
If you prerotate to 200 or below in a euro tub with the stick all the way back and move to full throttle-too quickly
There is a danger- I get that.
Once the gyro front wheel leaves the ground, the rotors are in effect conning and ready to fly. Progressively (few seconds) moving to full throttle allows the rotors to increase in speed to optimum.
The stick comes forward to arrest a nose high behind the power curve attitude and you fly away in ground effect to cruise speed and climb away.

it appears to me that after viewing many take off accident videos - in nearly 100% of those cases viewed, the accident would have been avoided by lowering the nose wheel.
In 2 of the cases viewed- clearly and aborted takeoff would have been in order.
Where have I missed the point?
 
Very formal, Vance – and a very good evening to you too!

You can never spend too much time on rotor management, the accident statistics are proof of that. Free-spinning rotors are the very heart of gyro flight and unique to our aircraft. Those blades are the boss and must be treated with due respect. If people think it’s not worth their time in learning properly then they need to go away and find another hobby. Gyros and impatience don’t mix.

This is a mindset that seriously needs to be addressed. Buy an aircraft and naturally they can’t wait to go out and fly. Fixed-wing, inert-wing no problem, open the throttle and off it goes. People really need to understand that that’s not going to work with the shiny new gyroplane they’ve just had delivered. Taking short cuts with a gyro will not have the desired effect. Like Fergus says, point them towards all the accident reports.

Everything is so over complicated these days, we can’t see the wood for the trees. Don’t get too bogged down with all the different POH – all gyroplanes have a rotor blade and that rotor blade will behave more or less the same, regardless of what flavour airframe is hanging from it. It’s impossible to write a procedure for every nuance of rotor handling, some of them are just too subtle to explain, but by repeatedly doing it for real with no other distractions, it becomes intuitive, second nature and applicable to all free-spinning rotor discs.

Yes, most two-seats are too tall to hand start but that doesn’t mean it can’t be taught. All that’s needed is a simple boom trainer attached to a car (front or back), with a few action cams in relevant places so they can review from different angles. It worked in the sixties so with all the kit available these days it should be a doddle to create fixed boom trainers, allowing students to experience real blade handling (including incipient flap) in a relatively safe environment. Cheaper than doing it in a two-seat, less risky and all they have to concentrate on is what the rotor blades are telling them. And it’s fun!

Two weeks concentrated manual rotor handling and aerodynamic spin-up practice up and down the runway in varying wind conditions – no instruments! Get them tuned into the rotors themselves, first and foremost, then an additional exercise every so often to reinforce. It will save them a set of rotor blades (at least), maybe several months grounded while their machine is rebuilt, and definitely many thousands of pounds/dollars/euros in repair bills.

Rotor handling is an art form, a real skill that comes with patience but not only that, it’s interesting and great fun to master. Perceptions need to be changed, and fast.
 

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In a word-
You would have to try to get them to flap.
If you prerotate to 200 or below in a euro tub with the stick all the way back and move to full throttle-too quickly
There is a danger- I get that.
Once the gyro front wheel leaves the ground, the rotors are in effect conning and ready to fly. Progressively (few seconds) moving to full throttle allows the rotors to increase in speed to optimum.
The stick comes forward to arrest a nose high behind the power curve attitude and you fly away in ground effect to cruise speed and climb away.

it appears to me that after viewing many take off accident videos - in nearly 100% of those cases viewed, the accident would have been avoided by lowering the nose wheel.
In 2 of the cases viewed- clearly and aborted takeoff would have been in order.
Where have I missed the point?

There are two main types of screwed-up takeoffs.

One is where things are ok until the nosewheel rises. Failure to limit the rise can result in over-rotation causing tailstrike and/or groundstrike.
There are a few examples of these on youtube. This is probably what you have seen.

The other main one is where the pilot fails to bring the stick back, accelerates down the runway, realises his mistake, and instinctively 'corrects' it
by pulling back the stick. This results in immediate destructive flapping. I have never seen this type on camera, although there are many verbal
eye-witness and pilot reports of this.

Most eurotubs don't allow prerotation with the stick back, which contributes to pilots forgetting to pull the stick back after prerotation.

Once the rotor is lifting the full weight of the gyro without problems, it is unlikely to encounter flapping, without some very rough handling.
 
Interesting sentence.

Outweigh, perhaps, replace, no.

The problem is that they can't properly use the data because they don't have a proper grasp of the theory, within which the data makes sense. Data on its own is just numbers.
You can bypass the theory with POH numbers and procedures, and it mostly works if the pilot follows it.
We read about the results when they don't.

Your POH should produce results similar to the Magni, in theory(mine). Better than the other competition, anyway.

Rotor handling and rotor flap can be easily demonstrated on a static rig in a light breeze. Done it with a Bensen gyroglider tied down.
The problem is that it may be forgotten over time without practice. But it should produce a reflex action to push the stick forward.

Well Greg is the mainly the instructor who taught these guys. So he is by no means a Euro instructor. And demonstration of a light flap is done for everyone by most instructors I know. I think this is a wrong impression by many that today’s instructors are not demonstrating the type of flapping you are talking about. All the ones I trained with did.
In our case all of these are from outrunning the rotor or not having enough rotor RPM on gusting day and all of takeoff. All pointing to not having enough Rotor RPM cushion. I know what Magni instructors in the US teach. They teach to have more rotor RPM before starting to move. There is more cushion to start with.
 
If you see folks doing that, it is probably just a hangover from prerotating by hand, where you would advance very slowly with a very small amount of backstick to get the rotors 'over the hump' in calm conditions.
Good point made there. If people have learned without pre-rotators then they inevitably begin with only the low RRPM’s obtainable by the ‘Armstrong’ method. And, these will also be governed by the type of rotors installed. Light rotors such as Dragon Wings are almost impossible to pat up though I have seen it done once, and even then a great deal of time and effort was taken.

Once the blades have been patted up as fast as they can be then the pilot moves slowly off with a fairly cautious angle of attack on the disc and feeds air into the disc gradually building up speed and disc angle to accelerate the blades smoothly, and avoiding any onset of blade flap/sail.

The wind speed when stationary plays an important factor, as it is possible in high winds...say 19-23kts to get blade flap/sail by simply bring the stick back too quickly before even moving. The important thing to keep in mind is the volume of air being allowed through the rotor disc for the rrpm at the time, and the variables are, the disc angle, RRPM, and airspeed through the disc, which itself is a function of the wind speed and direction and the gyro’s speed and direction.

Many pilots who learned without pre-rotators probably tend to rely less on the pre-rotator, or, tend not to use it to excess, simply to prolong its life, unless, they are trying to minimise take off distance.

If however a simple warning device can be made, it can only increase the safety margin.
 
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