accidents.. areas to avoid your advice

SandL

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When I went from fixed wing to gyros the first thing I did was get back copies of PRA mag and UK mags and read all I could paying special interest to prevoius accidents.
Above all else I did not want to wrap up my machine and thought that most "accident types" had already happened to others. So if I activly avoided those areas where others have been caught bofore maybe I can learn and keep my gyro in looking like a gyro. I also read forums such as this one.

So I hope this thread will act as a description of accident types from peoples memory and experience.
please pass on your advice and experience relating things to avoid

most classic accidents seem to fall into one of this list, maybe I have missed some

neg G PIO, PPO torque over
flight behind drag curve
brittle fuel sight tube becoming detatched in flight
other "engineering" and build issues
design issues (eg rudder too small, no HS, HTL leading to PIO)
cabin door opening in flight
hypothermia
tools left on the engine going throught the prop
low level flight into wires
self training
flying whilst intoxicated
engine failure over unfriendly terrain
gyro runaway during thrust check
non castoring nose wheels
first flight test flying of a new gyro
wire strike
medical issues
pushing ahead too fast on training
flying fast down wind refering to ground speed not airspeed.

anymore classic accident areas to avoid ?
 

ferranrosello

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I would like to know if someone has any reference about an accident or aircraft damage caused by overloading the rotor.

Do you have any referece?

Ferran
 

ckurz7000

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Overloading the rotor is pretty hard to do, Ferran. The margin of safety prescribed by Section T is usually more than you can get by pulling a tight turn, which gets you at most up to 2.5 g or thereabouts. The only way to overspeed the rotor would be at high density altitudes pulling a lot of g's. Never heard of such an accident.

-- Chris.
 

ferranrosello

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Yes, Chris, this is what I believed...

But are you sure that is not possible to overload a rotor? Imagine that you are flying very fast.

What would happen if you pull the stick as fast and as hard as you can?

I know that this is not the way to control any rotor. But I´m trying to understand something that by now I´m not able to understand.

Ferran
 

WaspAir

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Imagine that you are flying very fast.

What would happen if you pull the stick as fast and as hard as you can?
Don't expect the rotor to over-g itself. It's not like a separate elevator that can command a fixed wing to very high sustained loads. Rotors tend to fall through and won't sustain high loads.
 

WaspAir

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For the list:

poor rotor management in take-off run / spin up

P.S. Did we get poor weather decisions in there yet? I know of a perfectly airworthy A&S18A that was flown into a hillside on a night cross-country in foul weather.
 
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birdy

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What would happen if you pull the stick as fast and as hard as you can?
If you pulled back that fast youd get cyclic stall. [ not rotor overload]
But, if you kept the rate just below the CS rate, youd just fall through till they caught up. Thats the inherant safty in rotors.
 

Doug Riley

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Jim Vanek experienced progressive cracking of the hub of his Skywheels blades. Jim is famous for looping gyros -- a maneuver that obviously requires a rapid pull-up. So he sort of over-loaded them, although the designer probably didn't have looping in mind. A rotor that increases its RPM slowly when the disk AOA increases (i.e. because it's heavy) is more prone to this kind of over-loading than a light one that spins up almost instantly.

A couple people have had loose ropes fly up into the rotor, catch on a blade and wind around the mast. In one case, IIR, the culprit rope was the tow-rope of a gyroglider; in another, a rotor tie-down that blew out of the pilot's pocket; in a third, a Rotax pull-start rope that got free of the recoil housing.

A cyclic -- or precession -- stall is a stall of large portion of each rotor blade in turn during as it sweeps through a given portion (sector) of the rotor disk, e.g. between 7 and 11 o'clock. It produces a serious imbalance of forces across the rotor disk, resulting in destructive flapping.
 

SandL

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adding to the list of accident types

adding to the list of accident types

so we can add
weather
rough handling
ingestion of objects

so could we then say a flight like this has statistically little chance of a broken machine.

if you have good steady training, from a CFI are healthy, not intoxicated and the weather is good... (have removed fixed wing natural habits)
Then if the gyro is designed correctly, and a thorough preflight is done
a take off is performed, without flapping, not behind the drag curve with good lookout, flight is carried out avoiding PIO and PPO paying careful attention to airspeed and prepared for an engine failure so flight over friendly terrain only. followed by a landing into wind, stick forward before the blades slow, slow taxiing and shut down

in that flight would all the high accident statistics areas have been avoided ?

My thought is any deviation from that low risk flight profile increases risk.
Dont get me wrong I do not circuit bash I'm just looking at statistical chance and being aware that maybe deviation from totally safe needs extra risk managements eg on a cross country flight where terrain, weather, fuel and engine reliability come more into play. If I choose to go low level then I add wires, Terrain and weather can become more critical. so risk can be managed

I'm just thinking that a new gyro person could possibly see and avoid a poor flight profile, design and build it yourself, teach yourself, history of fixed wing takeoff behind drag curve etc we all know that person is very unlikly to complete an accident free flight. I'm thinking that if a new to gyros person could see real facts and figures it just might slow them down a bit and reduce accidents.

your thoughts and comments would be welcome
 

ferranrosello

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Sandl, I appreciate very much your interesting approach to reduce accidents.

My thought is that a lot of accidents are due purely to human error. So, the best way to reduce accidents is to put as many barriers as we can to these errors. This is the main sense of having procedures and a well-established safe routine practices when we are going to fly.

Talking about autogiros I have an additional concern: I believe we still don´t know perfectly what all flight limitations are.

In helicopters is accepted that is possible to break the aircraft by too abrupt control inputs. Talking about gyros it seems that they are magically immune to any problem in this case. But I believe that this is not the case, and that everyone flying an autogiro can kill himself by a too hard cyclic control input…

This question is seriously sensitive when we talk about fixed wing pilots flying gyros. They are used to fly with much wider control inputs than those required in a gyro…

This question is especially dangerous when we talk about autogiro capabilities to deal with very strong wings and turbulent air. This is not totally right. To do it safely we need a very accurate airspeed management, if not we can get killed easily.

Ferran
 

Steve_UK

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I'm not a pilot but have been lucky enough to fly in Mi-24 Hind, Mi-2, Mi-17, Lynx HAS3, Gliders, GA
Hi


""tools left on the engine going throught the prop""


add helmet ( ie tools or helmet ) coming off and going through the prop

bird strike ?

Ignoring MTOW - overloading ?

Running out of fuel ?

Fuel line blockage ?



Regards


Steve
 

birdy

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In helicopters is accepted that is possible to break the aircraft by too abrupt control inputs. Talking about gyros it seems that they are magically immune to any problem in this case. But I believe that this is not the case, and that everyone flying an autogiro can kill himself by a too hard cyclic control input…

Too agressive control inputs ina choppy can mast bump [ cyclic], bog the engine [collective], over speed the rotor [ collective] or loose TRE [ peddle].

Too agressive control inputs ina gyro can cause cyclic stall [ cyclic ], over coneing [ cyclic], torque over [peddle] or lateral drag over [ peddle].

Theres many weays for a pilot to stuff it up in both machines, tho the gyro is generally more forgiven.
 

Doug Riley

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SANDL, both PIO and PPO are the result of design defects. No student gyro pilot should need to worry about them. The fact that sudent pilots DO have to worry about them is a result of the prevalence of amateur and "copycat" designs.

Igor Bensen, a professional engineer, should have known better than to release (or keep on the market) a gyro design that was prone to these problems. He certainly knew how to fix them but, for various un-scientific reasons, double-talked instead of doing the right thing. We were left with a flawed "legacy," which remains today.

So, if you truly select a competent design, you can cross off PIO and PPO avoidance from your list of things a gyro pilot must consciously avoid.
 

Oskar

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Getting caught out by low level wind change and ending up with close to zero airspeed at 20ft.
Landing on a beach that looked like hard sand but was actually soft sand...
 

ferranrosello

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I have a question (of course a difficult one).

Our general knowledge is that to unload the rotors is very dangerous. It is dangerous for all kind of seesaw rotors, but it is probably most sensitive to gyros, because they have auto rotating rotors with a very special control system.

In spite of these notable limitations we know about it because of lots of tragic accidents that have happened. But all the explanations about this problem are related to PPO’s and PIO…

But with the new stable airframes, with good HS and centered or nearly centered propeller thrust lines, having an unloaded rotor is still a very risky situation suitable to end in a tragedy.

But my question is:

What is the behavior of these stable machines with unloaded rotors?

These are my thoughts on the matter:

I guess that at the beginning they will try to follow a 0g curve flying path… Can anyone imagine what would be the end of this flying path?

I guess that during this 0g curve the pilot can do nothing (no rotor trust, no control). And that the HS will keep the machine flying in the direction of the relative wind. It seems to me a non recoverable situation which has to end with the autogiro pointing directly down.

I guess that during this unloaded flight path the gyro will have to accelerate (because it is a 0g curve). And because of that at any moment, the rotor will start to flap back, and increasing the rotor disc pitch angle, which will reload the rotor.

At this moment the pilot will be pulling the stick against the rear stop (something natural because he wants desperately to raise the nose).

But I guess that during the 0g curve flying path the rotor will have lost a lot of rrpm. Now the rotor is reloaded but without enough centrifugal force to tighten the rotor blades…

I think that this picture could explain the last autogiro’s accidents in Mallorca and in Germany… The new gyros won’t PPO. But what are they going to-do?

Ferran
 
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Doug Riley

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Ferran, I can't speak specifically to accidents involving Euro-gyros. I've had a total of one flight in a Magni M-16, nothing more in such gyros.

A stable design SHOULD include a nose-up aerodynamic bias built into the airframe. That is, with zero rotor thrust, the frame should pitch up. This can be accomplished with a small amount of negative incidence in the horizontal stabilizer, just as it is in FW airplanes.

With such a built-in bias, the aircraft will still follow a ballistic trajectory when rotor thrust is interrupted, but the H-stab will rotate the nose up. If the pilot holds the stick still, the rotor will follow cyclically and re-establish a positive disk angle of attack.

What if the pilot lets go of the stick? With a Bensen-type gimbal head having excess offset and a rear trim spring, the rotor will tilt aft in zero G conditions.

It's still possible to interrupt flow to the rotor long enough to lose a critical amount of RRPM but, with proper frame design, doing so requires such a perverse, aggressive set of control inputs thta it is unlikely to happen by accident.

The other issue needing attention is engine torque. Large tail surfaces, perhaps with an anti-torque bias, immersed in the propwash, can solve this problem as well.
 

ferranrosello

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Doug, thanks for your very clear answer.

But... Can the airframe controls the rotor disc AOA when it is totally unloaded? In other words. The rotor disc cannot control the airframe attitude anymore. The HS can raise the nose. But Do you think that this is enough to rreload the rotor, that to say to change the rotor disc attitude?

Thank you very much for your help.

Ferran
 

cburg

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add...taking off with high speed pre-rotator enguaged...did it once...ok, but don't want to again.
 
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