Understanding Gyroplane Flight Controls.

Vance

Gyroplane CFI
Staff member
Joined
Oct 30, 2003
Messages
18,357
Location
Santa Maria, California
Aircraft
Givens Predator
Total Flight Time
2600+ in rotorcraft
I spent some time with 35 NTSB accident reports that had final reports dating back to the beginning of 2017 as a part of what John Rountree is trying to do to reduce accidents and reduce insurance rates.

https://www.ntsb.gov/_layouts/ntsb....?queryId=ae9844d0-2462-4c71-81af-4bcd6f5893e3

I found that using the final reports reduced the ambiguity of the reports and led to a clearer understanding of the accident chain.

The average age was 61.5 and the average flight time removing two outliers was 81.5 hours.

Five involved student pilots.

Two were control failures.

Twelve were takeoff accidents.

Eleven were landing accidents.

I felt twenty four of them had to do with a misunderstanding of how the flight controls of a gyroplane work.

It seemed to me like this would be a good place to start in preventing accidents.

Please post a constructive divergence of opinion if you have one.

In my opinion after liftoff the cyclic manages pitch and direction of flight. Pitch is what controls airspeed and the lateral cyclic position is what introduces bank and bank manages the direction of flight.

The cyclic does not control the direction of the aircraft before liftoff.

The throttle controls thrust. More thrust at a specific indicated airspeed increases altitude. Less thrust at a specific indicated airspeed reduces altitude. Bank requires increased thrust to maintain altitude at a given indicated air speed.

The rudder pedals steer the aircraft during the takeoff roll. They do not steer the aircraft once she is airborne and are used to manage yaw once she is flying.
 

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Address the take offs - was it performance issues or winds? or bad planning?
Landings? were they emergency or the result of take offs after bad preflight planning?
 
Address the take offs - was it performance issues or winds? or bad planning?
Landings? were they emergency or the result of take offs after bad preflight planning?

Takeoffs appeared to me to be primarily poor procedure, a lack of planning and a misunderstanding of what the controls did and how a rotor worked.

In my opinion the landings were poor skills, poor planning, and a lack of understanding about how the controls worked.

That is why I posted the link, so people could look for themselves.

I was surprised the reasons for so many of the accidents were so simple and so few.
 
not surprising that accident occur : example you forgot the main control : the throttle
The throttle controls thrust. More thrust at a specific indicated airspeed increases altitude. Less thrust at a specific indicated airspeed reduces altitude. Bank requires increased thrust to maintain altitude at a given indicated air speed.
 
...The cyclic does not control the direction of the aircraft before liftoff....

Vance: In my experience, I found that the cyclic CAN control the direction of my gyroplane on the ground, when they are fairly well up towards, or @, flight speed. This is w/ the cyclic w/ in the range of from fully back, or any distance forward up to the usual level flight position.

This is once the rotors are beyond the initial start up rpms supplied by the prerotator, and in the acceleration portion leading up to & including full flight rpms, while still "glued to the ground". Any tilting of the cyclic left or right moves the machine off in that direction on the runway. I didn't experiment w/ doing so abruptly, only gentle input.

This gyroplane (Sport Copter) has the usual castering nosewheel, which has no steering input involved by the N.W., just as your Predator is.

This movement is quicker as the ground speed is higher. It appears to me to be the same whether on pavement or dry lake bed surface. I haven't tried this on grass.

Tilting the cyclic while taxiing when the rotors are spinning fiercely, is a disconcerting feeling. It simply feels unnatural. In the air, this type of command input banks us into a turn, & feels natural.

A few times, I attempted to input a gentle, opposite rudder pedal movement to counter this, but "in the seat of my pants", this immediately created the sensation that I was close to toppling over, due to all the rotor mass spinning, tilted off in one direction, while I was initiating a command to steer the machine in a differing direction.

This feeling is just like after landing on the ground in higher wind speeds and making a turn on the ground, & when the machine becomes broadside to the wind direction w/ out banking the rotor disc into the winds. I once had one of my main wheels rise up off the ground in that situation, as I was stationary on the pavement, the beginning of a tipover. I immediately shoved the cyclic toward the oncoming winds, & the tire went back onto the ground. Scary!

That unsettling feeling of applying opposite rudder pedal to the direction of the rotor disc being tilted while they are up to, or near flight speed, is the same sensation I felt while flying while being balanced only w/ the right main wheel on the ground, in a slow right turn, on a dry lake bed, where no obstacles are present while doing so.

That feels as if I was right on the edge of being slammed to the ground as that right tire tucked under from the weight of me, the rotors, & the rest of the machine.

Balancing on the left main wheel in a slow left turn feels completely natural. The machine "feels right", just like cruising in the 45-55 mph range in straight & level flight does.

It feels like the gyro is on rails. I suspect that natural feeling is directly related to the torque forces of the engine/prop. Does anyone suppose the direction that the rotorblades spinning is also in that explanation?

I felt the sensation of being one w/ the machine in those situations. Very much akin to cruising on a motorcycle @ moderate speeds, where the smells of the landscape, the sound of the engine, & the amount of airflow on you is just right!
 
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Tilting the cyclic while moving on the ground w/ the rotors up to or @ flight speed has no apparent use on a airport, but I have used it to maneuver around a small, low patch of sagebrush I was headed toward while accelerating to take off A/S on dry lake beds. It still feels unnatural compared to using the rudder, but I added it when the rudder input was looking to be too little, too late as that clump of sage brush was "rushing toward me!

Tilting the rotor disc to avoid the sagebrush was then hoping to also become airborne b/4 reaching the clump, w/out resorting to pumping the cyclic aft to hop over it.

POOR PLANNING: Too hot of air temps (resulting in high D.A.), coupled w/ heavy machine, heavy pilot, too much fuel onboard, & taking off too near vegetation on the desert playa...
 
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Thank you for your input Kevin.

I have not flown a gyroplane that steers with the cyclic during the takeoff roll.

A common error that low time students make is to use right pedal and right cyclic on the takeoff roll when there is a wind from the left.

In my experience it leads to a slide to the right as soon as she lifts off.

I teach and practice that the gyroplane steers with the rudder when she is on the ground and with the cyclic as soon as she becomes airborne.

With a wind from the left most gyroplanes I have flown will need right pedal to remain on the centerline as they accelerate on the ground and left cyclic as soon as they lift off to remain over the centerline. I make a guess as to how much left cyclic to use in anticipation of the effect of the wind and if I lift off straight I know I have guessed correctly.

I feel a good example of a misunderstanding of how the flight controls work is the Cavalon crash in Nephi, UT 6/18/2019.

The pilot’s description of the event seems to me to be inconsistent with my understanding of how the gyroplane flight controls work during takeoff and his response seemed inappropriate.

“The pilot reported that, during takeoff, he rotated around 55 knots and that the gyroplane instantly yawed left about 45°. The pilot reported that he was "behind the power curve" and that the gyroplane could not climb or gain airspeed. The gyroplane began to descend, the pilot turned left, and the gyroplane landed hard and rolled to the right side. The pilot added that he believed that the gyroplane initially yawed left during the climb because of the "P-factor due to [a newly installed] more powerful engine" and that he failed to add right rudder input to correct. He added that it was his first test flight with the new engine.”

This is a pilot with 83 hours experience in a Cavalon at the time of the accident.

In my opinion the challenges for accident prevention training are how do you identify the misconceptions and how do you reach the pilot and alter his perception of how a gyroplane is controlled.
 
A roll command to the rotor will produce a yawing tendency on the ground to the extent that the center of the rotor is not directly above the aircraft's yaw axis. On the ground, this yaw axis is the main wheels (as long as they have enough weight on them, and friction with the surface, not to simply slide sideways). With Bensen-style tri-gear, the mains are pretty close to the rotor's center, so this yawing tendency will be weak.

OTOH, with tailwheel gear, the mains (hence the yaw axis) are well forward of the rotor's center. The result is that (1) the yawing tendency will be stronger and (2) the turn will be in the opposite direction than would be the case in flight. E.g., right stick will produce a left yaw. This could get fun in a Little Wing or other tailwheel gyro. Ground loop, anyone?

For my money, trying to yaw a gyro on the ground using the stick is playing with fire. If the gyro tilts up on one main in response to the side-stick, it will capsize once the its tilt angle exceeds the available rotor tilt (usually about ten degrees). It's a sickening feeling when your airframe tilts 12 degrees to the left, and all the right stick you've got isn't enough to keep the rotor from pulling you the rest of the way over... Bang!
 
Thank you Doug; as always well reasoned, well written and instructive.

I witnessed a tip over as you describe and it looked like it was in slow motion.

There were no gyroplanes with tail wheel gear in the 35 accidents I was looking at.

I suspect that is because they are rare and not because they are safer.
 
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A roll command to the rotor will produce a yawing tendency on the ground to the extent that the center of the rotor is not directly above the aircraft's yaw axis. On the ground, this yaw axis is the main wheels (as long as they have enough weight on them, and friction with the surface, not to simply slide sideways). With Bensen-style tri-gear, the mains are pretty close to the rotor's center, so this yawing tendency will be weak.

OTOH, with tailwheel gear, the mains (hence the yaw axis) are well forward of the rotor's center. The result is that (1) the yawing tendency will be stronger and (2) the turn will be in the opposite direction than would be the case in flight. E.g., right stick will produce a left yaw. This could get fun in a Little Wing or other tailwheel gyro. Ground loop, anyone?

For my money, trying to yaw a gyro on the ground using the stick is playing with fire. If the gyro tilts up on one main in response to the side-stick, it will capsize once the its tilt angle exceeds the available rotor tilt (usually about ten degrees). It's a sickening feeling when your airframe tilts 12 degrees to the left, and all the right stick you've got isn't enough to keep the rotor from pulling you the rest of the way over... Bang!
Exactly what I was going to say, after talking to a mate who fly's a little wing. He uses the cyclic to steer via yaw on the ground but as you say in the opposite direction. I was considering buying it so he was telling all about it.

wolfy
 
I feel a good example of a misunderstanding of how the flight controls work is the Cavalon crash in Nephi, UT 6/18/2019.
The pilot’s description of the event seems to me to be inconsistent with my understanding of how the gyroplane flight controls work during takeoff and his response seemed inappropriate.
This is a pilot with 83 hours experience in a Cavalon at the time of the accident.
In my opinion the challenges for accident prevention training are how do you identify the misconceptions and how do you reach the pilot and alter his perception of how a gyroplane is controlled.

These statements assume you have a willing subject to work with. The accident pilot may have been perfectly able to explain in a quiet classroom. or behind a computer at a desk, how his flight controls work. As you yourself can. Then with no experience on the aircraft he was flying (this was the very first flight for this Cavalon pilot with the newly fitted 915 motor according to his own NTSB statement).

Like many before him and many since they screw the pooch. Why? Not because they can't or don't understand XY or Z but because their experience is NIL and so their terms of reference are sub optimal.

Cyclic and throttle relationship is fine for elements of a basic flying course but once more beware the snags when we try and shoehorn everything under one phrase or set of actions. During the ground roll throttle/thrust is absolutely giving you acceleration and airspeed.

All these things combine to allow me the opinion that seat time is valuable and at times regulation is needed to save some from themselves.
 
For example I suspect this guy knows how to fly but can easily get snagged... see our slow fly past..

 
I'll make the same points I've made before to no avail.

The gyro accident rate is orders of magnitude higher than the FW rate for hours flown or new student starts.
FW have been teaching people to fly with a very high success rate and have taught tens of thousands more students than gyros.
Anywhere gyro training differs from FW training therefore should be examined VERY closely.

The three areas that I see that are most divergent from FW are:
1. Not as much ground school resources.
2. Limited availability of local instruction leading to cramming lessons and limiting time with an instructor in the next seat.
3. Teaching with crow hops.

Issue number 1 has recently been addressed with things like the Gyropedia program and Tim's US ground school course and those will certainly help.
Issue 2 remains a problem as most gyro instruction seems to be crammed into a week vacation at the instructors location and pressure on both student and instructor for student sign-off. Contrast this to the way most FW students learn with little time pressure and an airport near their home and they get signed off when ready and even after sign-off to solo will be back with flying with their instructor very shortly working on XC flight etc. So the instructor is constantly catching problems that develop.

I will come back to number 3 in a minute.

A huge cause of take-off and landing accidents then is what Vance posted above and is basically doing the wrong thing with the controls at the wrong moment. Hence Vance started this post about what the controls do.

Vance you can spend hours pedantically explaining things to someone on the ground, in this forum or in fight about which control does which and they may logically have a perfect understanding of it. Likely can repeat it back verbatim. YET THE FACT REMAINS THAT THEY ARE NOT MOVING THE CORRECT CONTROL IN THE CORRECT DIRECTION AT THE CORRECT MOMENT.

WHY? WHY? WHY?

Phil said it above- Not because they can't or don't understand XY or Z but because their experience is NIL and so their terms of reference are sub optimal.

Every sport is about muscle memory and sight picture. A ski racer going 80 miles an hour does not logically think about what he has do with his legs to make the next gate any more than a pilot logically thinks about what he does with the stick- If you are landing and drifting left your eyes see that sight picture and your brain tells your hand to move the stick right and it happens in a millisecond because you have done it that way a thousand times.

So why are low time pilots NOT moving the flight controls correctly in that millisecond- I believe it is not quite as Phil said their experience is NIL - it is because their experiences are contradictory. WHY?

BECAUSE OF CROW HOPS.

Crow hops- the one main difference between FW instruction with it's great safety record and Gyros with their terrible safety record.

In a crow hop you are teaching them to do all sorts of things they should not do in a regular take-off and landing. Not use full power- not climb out immediately at Vy, not fly a stabilized landing approach, not flare and feel the gyro settle- So you are building in all sorts of sight picture and muscle memory combinations that you do not want them to do in regular flying. It is no wonder that when flying on their own they move the flight controls in the wrong way at the wrong time becasue you have built into them many different and unnecessary experiences. They will for certain be slower to recognize deviations from correct flying.

If you always fly a stabilized pattern you will be quick to notice and correct any deviations whether by wind or control movement.
If you always do EXACTLY the same thing on take-off the same- but it some take-offs you are taught to reduce power for a crow hop and others not you will not recognize getting into a bad spot until it's too late.

Last time I mentioned this you explained you did crow hops cause it saved time- Please see item no. 2 above.

Last time I mentioned this someone else (who had been taught with crow hops) blithely replied crow hops are an essential skill of gyroplane flying- WHY? What is essential about them?

I've got a thousand hours and have flown all over and have never had to do one. I could certainly do one today but that is with tons of experience.

Rob
 
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I'll make the same points I've made before to no avail.

The gyro accident rate is orders of magnitude higher than the FW rate for hours flown or new student starts.
FW have been teaching people to fly with a very high success rate and have taught tens of thousands more students than gyros.
Anywhere gyro training differs from FW training therefore should be examined VERY closely.

The three areas that I see that are most divergent from FW are:
1. Not as much ground school resources.
2. Limited availability of local instruction leading to cramming lessons and limiting time with an instructor in the next seat.
3. Teaching with crow hops.

Issue number 1 has recently been addressed with things like the Gyropedia program and Tim's US ground school course and those will certainly help.
Issue 2 remains a problem as most gyro instruction seems to be crammed into a week vacation at the instructors location and pressure on both student and instructor for student sign-off. Contrast this to the way most FW students learn with little time pressure and an airport near their home and they get signed off when ready and even after sign-off to solo will be back with flying with their instructor very shortly working on XC flight etc. So the instructor is constantly catching problems that develop.

I will come back to number 3 in a minute.

A huge cause of take-off and landing accidents then is what Vance posted above and is basically doing the wrong thing with the controls at the wrong moment. Hence Vance started this post about what the controls do.

Vance you can spend hours pedantically explaining things to someone on the ground, in this forum or in fight about which control does which and they may logically have a perfect understanding of it. Likely can repeat it back verbatim. YET THE FACT REMAINS THAT THEY ARE NOT MOVING THE CORRECT CONTROL IN THE CORRECT DIRECTION AT THE CORRECT MOMENT.

WHY? WHY? WHY?

Phil said it above- Not because they can't or don't understand XY or Z but because their experience is NIL and so their terms of reference are sub optimal.

Every sport is about muscle memory and sight picture. A ski racer going 80 miles an hour does not logically think about what he has do with his legs to make the next gate any more than a pilot logically thinks about what he does with the stick- If you are landing and drifting left your eyes see that sight picture and your brain tells your hand to move the stick left and it happens in a millisecond because you have done it that way a thousand times.

So why are low time pilots NOT moving the flight controls correctly in that millisecond- I believe it is not quite as Phil said their experience is NIL - it is because their experiences are contradictory. WHY?

BECAUSE OF CROW HOPS.

Crow hops- the one main difference between FW instruction with it's great safety record and Gyros with their terrible safety record.

In a crow hop you are teaching them to do all sorts of things they should not do in a regular take-off and landing. Not use full power- not climb out immediately at Vy, not fly a stabilized landing approach, not flare and feel the gyro settle- So you are building in all sorts of sight picture and muscle memory combinations that you do not want them to do in regular flying. It is no wonder that when flying on their own they move the flight controls in the wrong way at the wrong time becasue you have built into them many different and unnecessary experiences. They will for certain be slower to recognize deviations from correct flying.

If you always fly a stabilized pattern you will be quick to notice and correct any deviations whether by wind or control movement.
If you always do EXACTLY the same thing on take-off the same- but it some take-offs you are taught to reduce power for a crow hop and others not you will not recognize getting into a bad spot until it's too late.

Last time I mentioned this you explained you did crow hops cause it saved time- Please see item no. 2 above.

Last time I mentioned this someone else (who had been taught with crow hops) blithely replied crow hops are an essential skill of gyroplane flying- WHY? What is essential about them?

I've got a thousand hours and have flown all over and have never had to do one. I could certainly do one today but that is with tons of experience.

Rob
Thank you for your input Rob.

I don’t know what avail you are looking for.

The goal of this exercise for me is to find a way to improve the accident rate for gyroplane with an annual advanced flying course.

I told John from the beginning that it would be difficult to identify weaknesses with a written test. I have often been surprised at the answers I get when I ask simple questions during the written pre-solo test and am trying to figure out a way to expand on the value I find in that.

It amazes me how few gyroplane pilots read and follow the Pilot’s Operating Handbook for their aircraft or fill in the V speeds during their phase one testing.

The written test I am imagining will only help to direct and focus the flying portion of the training.

Most of my clients initially have a hard time with power for altitude and pitch for airspeed. They know it intellectually but don’t feel it and when they are above the target altitude they lower the nose.

Because there are so few gyroplanes and gyroplane instructors I found I needed to create most of my own teaching aids.

The majority of my CFI mentors are fixed wing flight instructors.

I liked the teaching aids that I used when learning to fly Robinson Helicopters.

My fixed wing ground schools were not as good.

Gyropedia addresses this to some extent and Phil is working to better address the USA market.

Some flight instructors in the US are embracing The Gyropedia system.

I have not yet had success with it.

I recommend Tim’s course for my primary students for the knowledge test.

It would be nice if there were more gyroplane flight instructors and I have felt the pressure of time constraints because most of my clients are from more than 200 miles away.

Recognizing that is not the same as doing something about it.

I have a good friend who went from teaching in gyroplanes to teaching in fixed wings because he could make a lot more money with a lot less trouble and expense teaching in fixed wing aircraft.

That problem is not likely to go away any time soon. Reducing the accident rate and reducing the insurance rates may help.

The average flight experience of the accident pilots after removing two outliers (4,010 and 990 hours) and the students is 98.9 hours. I don’t know how that could be addressed with a regulation.

I was not taught crow hops in modified RAFs, SparrowHawks, Dominators or in The Predator and I do not teach crow hops to most of my clients.

I fly a consistent pattern with a stabilized approach as much as practical wherever I instruct.

Different people learn different ways and sometimes I find crow hops a useful training tool.

Crow hops are a part of transitioning me into a client’s single place and transitioning them into their gyroplane.

Crow hops were part of flight testing in fixed wings for my father.

It does not appear to me that any of the takeoff accidents involved anything related to crow hops.

I don’t know if anything will come of this effort.

I find value it the process.
 
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In virtually all of the videos as well as reports of gyroplane crashes in the last several years, it appears that it is a take off procedure of a two-place machine. Most of these are attempts to take off b/4 the rotorblades are up to flight speed & ends up too nose high, too slow, & w/ no directional control as it ends up going over on it's side. Each time I think it appears that an airplane pilot tried an airplane-style take off by fire walling it, paying not much attention to carefully winding up that flying wing prior to lifting off.

An observation of crow hops: The rotorblades are already up to proper flight speed while balancing on the mains.

Since bystanders of the two-place gyros take-off can easily watch or video this, we have more/better reports.

The in-flight break ups of many of these two-place enclosed machines are less noticeable, but still raise lots of questions as to airframe/ rotorblade integrity, as well as instruction techniques as to what to do when encountering an unusual situation.
 
In virtually all of the videos as well as reports of gyroplane crashes in the last several years, it appears that it is a take off procedure of a two-place machine. Most of these are attempts to take off b/4 the rotorblades are up to flight speed & ends up too nose high, too slow, & w/ no directional control as it ends up going over on it's side. Each time I think it appears that an airplane pilot tried an airplane-style take off by fire walling it, paying not much attention to carefully winding up that flying wing prior to lifting off.

An observation of crow hops: The rotorblades are already up to proper flight speed while balancing on the mains.

Since bystanders of the two-place gyros take-off can easily watch or video this, we have more/better reports.

The in-flight break ups of many of these two-place enclosed machines are less noticeable, but still raise lots of questions as to airframe/ rotorblade integrity, as well as instruction techniques as to what to do when encountering an unusual situation.
An interesting observation Kevin.

Again going back to 1/1/2017 and looking only at the accidents with final reports of the 12 accidents the NTSB fits into the broad category of takeoff accidents only four fit your description.

There were only two gyroplane accidents that fit into the broad category of cruise and one was a control failure and one was a loss of situational awareness AKA controlled flight into terrain.

“The pilot reported that he had presumed the terrain he was flying over was flat but later realized he had flown into rising terrain.”

At this time there are no final reports in this date range of a breakup in flight.

Rotor management is what I use crow hops to teach.

I usually resort to using crow hops when people are having trouble balancing on the mains and the initial spin up procedure or when transitioning someone into a single seat gyorplane.
 
I've got a thousand hours and have flown all over and have never had to do one. I could certainly do one today but that is with tons of experience.

Rob
Couple of quick question Rob.

Are you a gyro Instructor?

Do you teach single seat students?

Answer those two and perhaps the debate can continue.
 
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