Fatal in France

C. Beaty

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Juan de la Cierva, the brilliant Spanish pioneer of rotary wing flight, had encountered and solved most of the problems of gyroplanes in the 1920s/1930s.

Cierva solved the problem of propeller thrustline offset by tilting the engine/propeller combination to provide CLT and used differential tailplane incidence to eliminate propeller torque problems.

Now, 90 years later, those same problems go unresolved because the present day pattern is supplied by Bensen.

In Bensen’s defense, over-reflexed wooden rotor blades that prevented flight at much more than 60 mph and a high speed, low torque engine that didn’t produce much torque roll made a Gyrocopter fairly benign. Even so, a Gyrocopter was prone to torqueover and buntover in unskilled hands.

Horizontal stabilizers are essential to any flying machine but when used as a “fix” for design errors are in the same category as false teeth and wooden legs.

Gyroplanes evolved by byguess and bygosh “designers” continue to be lethal.

That’s why BJ Schramm’s statement; “look at the designer” is so relevant.
 

EI-GYRO

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Re the 'look at the designer' argument, Magni may score higher than we
think.

The Magni designs probably originated in the mind of Jukka Tervamaki, who
is a qualified aeronautical engineer.
 

Vance

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My Opinions and Observations.

My Opinions and Observations.

Vance,
I have not flown a MT but I have flown a Magni M-16, and it will nose up if you add power. This is not a question of opinions, is a fact. Besides, any gyro which pitches down the nose when adding power it is an unstable gyro. The Ela pitch its nose up. I guess that the MT would do the same thing. I’m totally sure that they don’t pitch down when you add power, Vance. I’m not going to discuss about if they are slight HTL or not: they are stable gyros because when you add power they pitch its nose up. Their HS is working perfectly compensating the HTL (overcompensating in the Ela’s case).

I have talked about this question because is a big misconception to think that shutting down power in the top of a bell shaped maneuver you will avoid PPO. In the Magni’s case this is uneventful. In the Ela’s, it is worse to pull back the power because is overcompensating and it will nose down too much (which is not very good if you are in a low g situation). Probably it is not a coincidence that all these accidents in short final has happen with the power at idle..

My opinion is totally divergent from yours. I’m going to put the things in this way: It is impossible to have a drag over if there is not a concurrent low g situation. This is a fact too, at least if we are talking about Ela’s. And this is the case in this thread. I’m an Ela pilot with a lot of experience in this aircraft and I can ensure you that it will not drag over in a normal 1 g flight situation.

Of course it can drag over in a very low g flight condition. If you want to discuss what is the cause of the control loss in this case you can. However my point is that all sustained 0 g situations conduct to a total loss of control. I know that you don’t believe that is possible to have sustained 0 g situations in a gyro. My answer to that is that more than half a second is a sustained 0 g situation, and unfortunately It is possible to have 0 g situations lasting enough to conduct to accidents.

JAL, I’m not talking about PPO. I’m talking about a 0g event that produces a loss of control. No 0g implies no loss of control: nothing happens.

It is very simple: every gyro control problem starts with a very low g situation.

Any way I understand your point about the forces acting on the pod that can trigger the drag over. However the control authority of the rotor will able to counteract this effect, except in too low g situations.
I agree with you and Chuck when you say that the HS is ineffective in a heavy side slip. However I totally disagree with the concept that in that case you will be flying a pure HTL.

The HS is still in its place under the effect of the propeller blow, Sir. Your explanation about the way in which the HS gives stability is nice. However there is an additional factor: our HS (Magni, Ela or MT) are providing a true negative lift, which compensates the HTL. That means that if you have power in a side slip you are not in the same situation than a HTL without HS. If you drop all the power to idle, then there is not HTL (no power no thrust).

You are flying MT’s. Please do the following test: at a secure flying altitude at cruise speed trim the gyro and don’t act on the stick. Then low the power to 3500 rpm and look what happens. Then come back your first power setting and you will get initial flying condition: cruising speed at leveled flight. Now add more power, say something like 5200 rpm.

I guess than in the first case your gyro will pitch its nose down (and in the second it will pitch up). This is important, because it dictates what you should never do to recover a low situation: reduce power.

These are my two points: 0 g is the main cause of control loss and we have to use the power in the opposite way that everybody thinks to recover very low G situations in these kind of machines.

Ferran
Without power it is impossible to have a Power Push Over (PPO). By definition power is required for a power push over.

Ferran brought up center of gravity in relation to thrust line as though he had measured it. I didn’t ask him to discuss it; I asked him to share the numbers.

We don’t know the cause of “all these accidents” and I didn’t know we knew the throttle setting on this particular accident in France.

I won’t discuss this particular accident because I know so little about it.

I feel Ferran may also be confused about a drag over; particular in a slip.

I feel Ferran is misusing the language again by redefining sustained as a half second. I suspect most well designed gyroplanes could manage a half second of zero Gs. I would define a half second event as a transient condition.

I have not flown an ELA so I don’t know anything about its flight characteristics. I have flown an M16 Magni near the gross weight limit and the one I flew pitched down at 40kts when adding power and pitched up when power was reduced.

There are many dead gyroplane pilots who did not get there beginning with a sustained zero G event even as Ferran defines it. I feel Ferran’s assertion that a sustained zero G event is the only way to get into trouble in a gyroplane is dangerous.

I feel Ferran’s fantasy that he can feel the approach of a non recoverable event is invalidated when experienced pilots crash a gyroplane. I suspect Ferran has no idea how close to a non recoverable event he has come. I feel a successful outcome of a maneuver does not necessarily indicate that it is safe.

In my opinion a “sustained zero G event” is not a necessary part of the accident sequence in a gyroplane.

In my opinion any gyroplane with the center of pressure below the center of gravity has a tendency to roll in a slip. I flew with low time gyroplane certified flight instructor in an MTO Sport and in my opinion it rolled when he demonstrated a slip to descend at 60kts indicated air speed. I felt we were near the limit of his ability to command the disk to counter the roll. We were probably sustaining more than .6 Gs even by Ferran’s definition of sustained in the gusty conditions. I asked the CFI about it afterword and he claimed it was a completely safe maneuver.

It is a lovely day and I am off to fly with my friend Bob.

Thank you, Vance
 
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C. Beaty

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Re the 'look at the designer' argument, Magni may score higher than we
think.

The Magni designs probably originated in the mind of Jukka Tervamaki, who
is a qualified aeronautical engineer.
The rotor system was designed by Tervamaki, a former Bensen employee.

The low slung Ferrari look with 12 inches* of thrustline offset seems to have originated with Magni.

*That number comes from measurements taken in Australia.
 
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Doug Riley

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Jukka Tervamaki is a real engineer -- the kind with a university degree and relevant work experience. He also wrote the first analysis of PPO that I can recall reading -- in the PRA magazine, about 1975. The gyros he built that formed the basis of the Magni had higher, smaller cockpit pods and longer nose-gear legs than the present-day Magnis.

Using a H-stab to counter the effects of a fuselage that's trying to pull the nose down is pretty standard stuff in aircraft design. Its done on boat-hulled amphibians such as the Lake and Seabee. These craft are, of necessity given their mission, both very HTL and very low-aerodynamic-center designs.

Many helicopters have a fuselage shape that tends to cause nose-tucking at high speeds, so their H-stabs are designed to create a down-force, too.

In my opinion (and Chuck Beaty's, obviously), creating a HTL, low-aerodynamic center fuselage for no reason more urgent than car-like styling is a questionable value choice. I'd be inclined to lay out the aircraft so that it flies the best, and educate the customers that this isn't a car and therefore shouldn't look like one. It's safer for the newbies to get rid of car-thinking as soon as possible anyway.

Clearly, however, the styling sells. If a designer is going to go the "flying sportscar" design route, though, he has a moral obligation, IMHO, to explore and deal with all the consequences (especially those that can kill somebody).

Recent crashes strongly suggest that this testing-and-correction has NOT been accomplished on some Magni clones, and that experienced pilots are going down as a result.
 

EI-GYRO

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Given that, to date, the Magni machines have not suffered the problems encountered by the 'clones', it may be that the term 'Magni-clones' perhaps
should be dropped.

It has always been my impression that there was more interaction between
Magni and Tervamaki than just the sale of a partial design.

I notice that the agency for Magni in the Nordic countries appears to
include a guy named Jukka.
 

C. Beaty

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The very different behavior of a Magni from its lookalikes comes entirely from its overbalanced rotor.

The Magni rotor has its CG well forward of its aerodynamic center. Behavior isn’t much different from a nose heavy FW airplane.

An upward gust, acting on the AC of the rotor, torsionally twists the blade nosedown, no different from a cyclic control input that tilts the rotor disc nosedown and heads it into the relative wind.

A disturbance that tilts the airframe is resisted by the rotor.

A cyclic control input by the pilot is resisted for the same reason, leading to a heavy stick. The rotor responds to cyclic input with greater lag; the offset between spindle tilt and rotor disc producing an opposing moment in the control system.

There have been reams of nonsense written about the heavy stick stick of a Magni based on a faulty Italian to English translation in the manual, titled “Frictionizing the controls” which should have gone something like; “reduce backlash while minimizing pivot friction.”

The heavy stick of a Magni is definitely not caused by binding of control linkages.

I don’t have the foggiest notion of whether overbalance was a deliberate design decision or that’s just the way things ended up. I do know that Tervamaki was employed at Bensen during a time when Bensen was experimenting with overbalanced rotor blades.
 

birdy

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Now, 90 years later, those same problems go unresolved because the present day pattern is supplied by Bensen.
I don't think you can blame ol Benson.
I think its the modern ' looks are everythn' mindset today.
If it looks sexy, its gota be good.
Back wen men were men, looks didn't come into it. It had to work first.

Think bout it, wots the first, most common comment you hear wen sumthn new comes out.
Youll never hear 'that will fly well.'
But you will hear the words "wow" and "sexy" among other fake crap.
 

C. Beaty

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Birdy, it’s like buying an electric can opener; no woman would buy an electric can opener that looked like a 1920s sausage grinder no matter how well it worked.

A gyro need not be ugly but it should look like it was meant to fly rather than go 200 mph down the autostrada.
 

birdy

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A gyro need not be ugly but it should look like it was meant to fly rather than go 200 mph down the autostrada.
Duno wot an autostrada. is, but ugly is only skin deep.
Besides, I cant see the ferel wen im sitn init. :)
Merry Xmas mate. :)
 

ferranrosello

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Ferran brought up center of gravity in relation to thrust line as though he had measured it. I didn’t ask him to discuss it; I asked him to share the numbers.

Sorry, but I don't know the exact numbers. My only point is that Magni has a higher Trust Line than Ela.

I feel Ferran may also be confused about a drag over; particular in a slip. Of course I can. But you could be confused too.

I feel Ferran is misusing the language again by redefining sustained as a half second. I suspect most well designed gyroplanes could manage a half second of zero Gs. I would define a half second event as a transient condition. Are you sure that all "well designed gyros" will endure a 0g situation lasting half a second? I simply don't know. Anyway, here I'm not talking about how much has to last a 0 g situation to produce a loss of control. I'm sure that half a second is enough to produce the tip-over a gyro that is performing a heavy side slip. If the gyro is performing a normal coordinated flight, I believe that the required time to lose control will be longer... however i don't know.

I have not flown an ELA so I don’t know anything about its flight characteristics. I have flown an M16 Magni near the gross weight limit and the one I flew pitched down at 40kts when adding power and pitched up when power was reduced. I have flown a Magni M16 and my experience is totally different. Maybe my memory is failing, or that the test conditions were different. I did the test with free stick. Anyway, I guess the a Magni pilot can tell us what is the real behavior.

There are many dead gyroplane pilots who did not get there beginning with a sustained zero G event even as Ferran defines it. I feel Ferran’s assertion that a sustained zero G event is the only way to get into trouble in a gyroplane is dangerous. You are right, there are other ways of getting killed flying a gyro, like hitting wires. My point is that all accidents that have happened because of a loss of control have started with a very low g situation. I’m pretty sure that if all gyro pilots avoided commanding low g conditions lots of fatal gyro accidents would never happened.

I feel Ferran’s fantasy that he can feel the approach of a non recoverable event is invalidated when experienced pilots crash a gyroplane. Sorry if I'm giving to you this idea. I have the same limitations that all other pilots. What I'm avoiding is getting in pilot commanded low g situations. I suspect Ferran has no idea how close to a non recoverable event he has come. I feel a successful outcome of a maneuver does not necessarily indicate that it is safe. I don’t know how to explain this. I'm not talking about a "single" maneuver. I'm talking about a lot of them, (hundreds or thousands?), Vance. And I have always felt in total command of the situation. I know, because I have done it, than in an Ela the limitation in side slip is because you run out of pedal. I have never run out of lateral stick (which would trigger a drag over). Of course there is an air speed limitation to conduct side-slipes.

In my opinion any gyroplane with the center of pressure below the center of gravity has a tendency to roll in a slip. Totally agreed. However if you are flying in 1 g you have full control authority to deal with this tendency. The problem is when you reduce the g, load, what implies a reduction in the control authority. I flew with low time gyroplane certified flight instructor in an MTO Sport and in my opinion it rolled when he demonstrated a slip to descend at 60kts indicated air speed. I felt we were near the limit of his ability to command the disk to counter the roll. We were probably sustaining more than .6 Gs even by Ferran’s definition of sustained in the gusty conditions. I asked the CFI about it afterword and he claimed it was a completely safe maneuver. Are you saying that the CFI was doing a side slip moving the stick to the opposite side of the slip (is the only way to get command problems…)? Sorry, but I cannot believe that. In a right side slip is the pilot who tilts the rotor to the right. If there is a rolling tendency (something that has not been demonstrated) the pilot will have to get rid of some right stick. Anyway 60 kts is out of limits to perform any side slip. The approach speed should be something like 60 mph or 95 km/h, far away of 60 kts (112 km/h)

It is a lovely day and I am off to fly with my friend Bob.
Thank you Vance. Enjoy your flight day.
 

Vance

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“Are you sure that all "well designed gyros" will endure a 0g situation lasting half a second?”

If I intended to write that I would have written it Ferran. I suspect most people flying a gyroplane in turbulence have experienced an uncomanded 16 foot drop indicating to me a low G to zero G event lasting a half second or more.

At one time I imagined that all low g events were stupid pilot tricks and I could avoid that problem by not being stupid. I have since experienced several environmentally generated low G events.

I feel understanding this is important because I have heard people who fly unstable gyroplanes say that they feel safe as long as they stay away from low Gs and fly inside the aircraft’s limitation.

I have not found a way to accurately predict turbulence.

“Are you saying that the CFI was doing a side slip moving the stick to the opposite side of the slip (is the only way to get command problems…)? Sorry, but I cannot believe that. In a right side slip is the pilot who tilts the rotor to the right. If there is a rolling tendency (something that has not been demonstrated) the pilot will have to get rid of some right stick. Anyway 60 kts is out of limits to perform any side slip. The approach speed should be something like 60 mph or 95 km/h, far away of 60 kts (112 km/h)”

I am not sure what you are asking Ferran. As we approached the airport at 1,300 feet AGL I returned control of the aircraft to the CFI because I usually don’t land other peoples aircraft. I had just wanted to get the feel of an MTO Sport and I could do that at altitude. The then pilot in command of the MTO Sport at 60kts indicated airspeed pointed the nose to the left and moved the stick to the left as the gyroplane tried to roll right in gusting conditions. We had not even entered the downwind and were making a non standard pattern entry. We discussed slips, pattern altitude and non standard pattern entries in our debrief and he felt slips were hazard free in an MTO Sport, pattern altitude was unimportant and non standard pattern entries were fine in a gyroplane. He is not someone I would fly with again.

Some of us are not familiar with your slip limitations Ferran.

”Thank you Vance. Enjoy your flight day.”

I did have a great flight although Bob didn’t show. Direct would have been a 44 nautical mile flight round trip to San Luis Obispo. Somehow through jubilance and abandon it became 213 nautical mile flight.

It was four hours and thirty four minutes of flying for what should have been an hour or less flying direct. I gave three people their first flight in a gyroplane.

Thank you, Vance
 

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Vance

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From the MTO Manuel

From the MTO Manuel

Side Slip in Gyroplanes
Excessive side slip has to be avoided at all means. Side slip can be safely performed the degree which is necessary for proper runway alignment for landing within limitations. Excessive side slip starts at a point where de-stabilizing effects of the balance out or even supersede the stabilizing effects of the stabilizer. Pilots being gyroplanes, especially those with fixed wing experience may not be aware of these limitations. When exceeding these limitations, be it by imitating ‘professionals’ or habits and control schemes from fixed wing aircraft, the gyroplane may enter where it is not recoverable any more. As the pedal control is rather sensitive and is crucial in high-performing gyroplanes, pilots should develop a feeling for side ‘automatized feet’ in order to maintain aerodynamic alignment and to compensate power-induced yaw couplings by anticipation as a conditioned reflex.
A note to training facilities and flight instructors: Due to their reduced stability, gyroplanes require active control to enter, stabilize and neutralize side students perceive natural discomfort in side slip. Depending on the situation, students erroneously make a wrong control input or freeze, especially when overchallanged,
stressed, or surprised by the situation. In our opinion flight training should focus necessity of correct alignment, the training of recovery procedures, and the development the right reflexes. Intentional side slip training as a normal procedure is considered critical as there is no instrument to indicate ‘safe’ boundaries. An experienced pilot from an imminent change in control response when limits are approached. however, may unknowingly or inadvertently overshoot the limits, especially when overly focussed on the touch-down zone and coming in too high.
Side slip may be performed as a part of the emergency training only, and within boundaries. The student must be briefed
to use gentle pedal input for initiation and stabilization
initiate side slip at or below 90 km/h and maintain air speed by using his perception speed, respectively speed sensation (for want of a working air speed indication)
not to rely on airspeed indication in side slip
never to perform abrupt control stick input into the direction of motion (to chase faulty speed indication)
It is highly advisable that the instructor remains light on the controls at all times.
 

Doug Riley

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I failed to heed this advice once when teaching a student in my tandem Dominator. The student was accustomed to FW ultralights.

I suggested that he gently feel out slips. He promptly yanked the stick to one side and stood on the other rudder pedal, at an indicated airspeed of about 75 mph. In the back seat, I felt as if the wind was crossing my face at 90 degrees to the aircraft's long axis. The aircraft banked gently but did not keep rolling. There was no instability or suggestion of instability.

I suspect that the Dominator's benign response to this over-control resulted from the location of the fuselage's center of aerodynamic pressure at or above the CG. This is a predictable byproduct of (1) placing the crew seats and frame high enough relative to the engine so that the CG is above the propeller thrustline; (2) limiting the side area of the fuselage, especially below the CG, and 93) using a tall vertical tail, which locates nearly half of the fin area above the CG.

Professional gyro designers in the Cierva tradition used such tactics as mounting a vertical fin above the rotor spindle, and adding large dorsal fin area just below and behind the rotor, to bring the fuselage's center of pressure higher and thereby reduce or eliminate slip-roll coupling. Winged gyros had a large dihedral angle, making divergent slip-roll coupling unlikely.

It's safe and inexpensive to test for slip problems with scale models in a breeze.

Vance is correct that you can't avoid all zero-G situations. You must design so that the craft can tolerate a turbulence-induced zero G event.
 

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I think, side-slip should be just plain forbidden in gyroplanes.

What is actually the need for a side-slip, when you can do a vertical auto-rotation descent to the necessary altitude over the runway to perform a perfect landing?

At touch down, to get out of crab, few inches over the ground, you can align with the runway.

Any other use of sideways flying is unnecessary in a gyroplane and should be avoided.
 

scandtours

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Side slips can be safely performed on gyros if we know how and ‘’when’’ (upwind? side wind? downwind?). It is trickier with two o.b. of course, and it has to be done at much higher altitudes. It’s like you are flying at the ‘back side of the power curve.’ .... Full power without results
When initiating a side slip by moving the stick right or left and use opposite rudder what happens? Did you ever thing about it? I did not n either, but let’s say in a left side slip, the blades are tilted to the left side and air speed from the left increases (left side of gyro) and wind forces will impact the upper surfaces of the rotor blades,(negative.)
It will not be exactly as image shows below.
Maybe I am wrong so, better follow manufacture’s manuals…
 

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PW_Plack

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I think, side-slip should be just plain forbidden in gyroplanes...What is actually the need for a side-slip?
Forbidden by whom, the government? Be careful with that path because the logical extension is, what is actually the need for a gyroplane?

I suspect that governments would include resistance to slip-roll coupling as a certification standard before they would pretend they could stop the maneuver with a regulation.
 

Doug Riley

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Paul K., perhaps a gyro used for hauling mail could be placarded against slips. But gyros are marketed as fun, maneuverable craft. They are so inefficient (from a commercial point of view) that fun maneuvering is probably the best use for them! If so, then prohibiting slips -- a common maneuver -- is inconsistent with the mission.

I believe that researching the problem, and designing it out if possible, is a more logical approach than teaching students to tiptoe around this and other "coffin corners."

A gyro in a level, or descending, slip is still moving forward much faster than it is moving sideways. I don't think we have to worry too much about the rotor disk achieving a zero or negative angle of attack unless, perhaps, the maneuver begins at the top of a "zoom" climb.

I've done slips during vertical descents without a problem. The gyro then has no forward airspeed, but it is falling like a brick, so its disk angle of attack is actually quite high in a vertical slip.

As with PPO, the main culprit in slip-roll coupling instability appears to be fuselage and tail design. There's no good reason to tolerate a design that creates such a problem in an otherwise tame maneuver.
 

birdy

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Paul, I can think of a dozen needs to slip, without getn a sor head.

As for ' air over the top', I don't think so.
Soon as the airflow changes from front on to to the side, the natural teeter action will compensate, no matter how fast you yank the stick.

As Doug says, just build the f$$$$n thing with functionality the highest priority, and aesthetics a distant last.
 
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