Fatal Gyro Accident in Putnam County, Fl

[Philbennett]

I see another AR down in Utah from the pic it looks like a new 915 unit? What the hell is going on? We profess and teach the safety of these things ...

Funny old world but never-the-less... I got this on my YouTube channel:-

This is bad advice. I could not convince my dad to properly raise the nose and balance on the mains. Doing it correctly requires skill and feel. He preferred to keep the nose wheel on the ground until around 60mph, and then lift like an airplane. His technique killed him yesterday. Rotorflap on takeoff probably caused a rudder strike and rudder damage, and then what appears to be the loss of the rudder between 50-100 feet of altitude, resulting in complete loss of control. I will post video of his crash later on rotary forum. Proper technique is to balance on the mains to keep the rotor accelerating and loaded, without letting the nose get too high. It requires skill and feel, and not everyone is capable of this.

 

[Doug Riley]

Yes, it's terrible advice. But somehow it seems to have crept into the training syllabi used to teach people to fly fast Euro-tub style gyros. These are not FW planes, and should not be flown like one. The only exception might be gyros with true full-RRPM prerotators, such as the McCulloch J2.

This distinction goes all the way back to the 1930's. Amelia Earhart flew a gyro as if it were a FW, and had some upsets. Johnny Miller OTOH did vertical-descent landings, as well as loops, and did not have upsets. He knew how a gyro worked and how it wanted to be flown.

Is gyro flying safe? IMHO, there is insufficient real engineering and testing done on many models, even the obscenely expensive ones. The fact that we have $100K+ craft for sale as completed, new aircraft, but that will roll over in the air and crash if slipped, is proof that some designers are merely eyeballing their layouts and skipping over the basics. A craft sold for mere recreation by low-time pilots should be designed highly idiot-resistant.

We still don't have numerical data on exactly what happens, and what can be done about it, when a teeter-hinged autogyro rotor is exposed to a negative disk angle of attack. What we have instead is shattered wrecks, a few grainy videos, some back-of-an-envelope calculations, and lots of anecdotes. This sort of "black hole" of ignorance existed for subsonic FW planes up to about WWI, but it hasn't been true for them since then. We can't say the same for small autogyros.

Some would consider this state of ignorance "dangerous." It certainly demands extra caution and self-education to achieve reasonable safety. But even then, you are still riding a bike in city traffic.

 

[dinoa]

Could the high power and thrust to weight ratio have something to do with it?

 

[Philbennett]

I don't know what has happened here [Utah accident not the FL one, although I have no idea whats happened here either!] . What I do know is that I do not know a single instructor of gyroplanes that advocates some form of FW "rotate" to get airborne.

I know plenty of people that suggest a flatter disc attitude at certain RRPM to reduce aerodynamic drag and to promote a cleaner take off attitude but that does not and can not either sail the rotor blades nor lead to any rotor to bodywork contact because of the mathematics of forward airspeed and RRPM driven tip speed make it impossible.

 

[fara]

Hi Guys:
Its a very sad day. The accident in Utah though is on video. There is more video than you may see on TV or youtube. There are also on ground pilot eyewitnesses. We are cooperating with NTSB and facts will eventually come out. We don't ourselves have the whole picture yet

About putting the nose wheel down and go to 60 mph to liftoff unfortunately I know first hand this was being taught by some instructors a while back (2014/2015) and they happen to be AutoGyro dealers at the time. Though I knew AutoGyro absolutely did not recommend that way of taking off. But that's another story. Simple fact is rotors have to be loaded on takeoff or in the air. If you unload them, you have an aircraft without wings with rotors flapping around

 

[Philbennett]

You suggesting that the filmed element of the take off was the second bite of the cherry and something happened ahead of that film?

 

[fara]

You suggesting that the filmed element of the take off was the second bite of the cherry and something happened ahead of that film?

That video is longer than what you see. NTSB has the whole video. That's all I know

 

[Philbennett]

Rog. Just there seems to be an early view that focuses upon the take off and blade sailing/rotor/rudder contact but the unstick seems pretty clean in that film and usual blade sailing leads to disymetry of lift, rotors hitting teeter stops and a roll over. The aircraft doesn't seem unduly fast either. Just saying from what I can see...

 

[Vance]

I don't know what has happened here [Utah accident not the FL one, although I have no idea whats happened here either!] . What I do know is that I do not know a single instructor of gyroplanes that advocates some form of FW "rotate" to get airborne.

I know plenty of people that suggest a flatter disc attitude at certain RRPM to reduce aerodynamic drag and to promote a cleaner take off attitude but that does not and can not either sail the rotor blades nor lead to any rotor to bodywork contact because of the mathematics of forward airspeed and RRPM driven tip speed make it impossible.

In my opinion a two blade semi rigid gyroplane rotor becomes divergent when the critical angle of attack of the retreating blade is exceeded.

There are many ways to achieve this.

Contributing factors are not enough rotor rpm for a given indicated airspeed, disk angle and turbulence.

Reducing the disk angle to reduce the drag allows increased aircraft acceleration and decreases rotor acceleration.

In my opinion reducing the disk angle to reduce the drag puts a pilot closer to trouble.

Reducing the disk angle to balance on the mains is a very different thing and a nice way to listen to what the gyroplane wants for a successful takeoff.

In my opinion the best practice for takeoff is to follow the procedures outlined in the Pilot’s Operating Handbook for the particular make and model you are flying.

 

[Philbennett]

Your opinion is an opinion, mathematics are absolute and the rationale for your view on the ability to reduce the disk angle while balancing upon the mains, you just didn't relate that to maths. However if you recognise the maths of the situation you might appreciate you can do it at other times.

 

[Greg Vos]

In my opinion a two blade semi rigid gyroplane rotor becomes divergent when the critical angle of attack of the retreating blade is exceeded.

There are many ways to achieve this.

Contributing factors are not enough rotor rpm for a given indicated airspeed, disk angle and turbulence.

Reducing the disk angle to reduce the drag allows increased aircraft acceleration and decreases rotor acceleration.

In my opinion reducing the disk angle to reduce the drag puts a pilot closer to trouble.

Reducing the disk angle to balance on the mains is a very different thing and a nice way to listen to what the gyroplane wants for a successful takeoff.

In my opinion the best practice for takeoff is to follow the procedures outlined in the Pilot’s Operating Handbook for the particular make and model you are flying.

What ?

 

[Vance]

Your opinion is an opinion, mathematics are absolute and the rationale for your view on the ability to reduce the disk angle while balancing upon the mains, you just didn't relate that to maths. However if you recognise the maths of the situation you might appreciate you can do it at other times.

Please share with us the infallible math you are using Phil.

 

[Vance]

What ?

I don't understand your question Greg.

 

[Philbennett]

Please share with us the infallible math you are using Phil.

Well it was a serious point actually. I'm not sure to what extent you may or may not agree with any of this but it was discussed to some extent on another thread with talk of tip speed ratio i.e. the speed of the rotor at its tip v the speed of the aircraft as read from the ASI.

If you consider your very own point made just a moment ago:-

In my opinion a two blade semi rigid gyroplane rotor becomes divergent when the critical angle of attack of the retreating blade is exceeded.

There are many ways to achieve this.

Contributing factors are not enough rotor rpm for a given indicated airspeed, disk angle and turbulence.

Suggests that you have some recognition of the same, yet there are a mixture of issues in your view.

If we deal with what actually creates the issue of blade sailing in your two blade teetering rotor; it is merely because the flapping required in the rotor to "equalise" the disymetry of lift is constrained by the teeter stop, that gives some feedback via the stick and because its onset is very fast [usually because the pilot has pulled the stick back creating more alpha to flap out and rotors have become slow] the aircraft rolls due to disymetry of lift [now unable to have been equalised via normal flapping/teetering [language] action of the rotor] and the aircraft thrashes itself to some form of damage on the ground.

The alternative is the rotors are very slow but so is the airspeed [ground speed] and the rotors smash the tail to pieces.

I can not find a case where the combination is such that the rotors have flapped, the aircraft didn't roll or the blades were fast enough to get airborne but we had smashed the tail to pieces and then we fell out of the sky. [if someone can point to an investigated accident that contradicts that view please refer me to the report].

That doesn't happen because once the rotor has accelerated it will keep doing so to flying speed as long as the tip speed ratio is favourable.

Edited to add the quote from the prior thread in September on same subject:-

As you know, the divergence of the flapping angle is due to the stall of the retreating blade. Therefore the acceptable limit of tip speed ratio also depends on this angle.
Unfortunately, the angle of attack of each blade element changes periodically during rotation, which creates an hysteresis: Later stall and re-stall. The stall angles then become difficult to predict for me, and thus also the critical ratio of divergence.
But to give you an order of magnitude, I find that in a situation quite usual for our gyroplanes (A.o.A disk at about 20°, aerodynamic pitch of the blades at 3°, and assumed stall angle of 13°) the calculated divergence seems to appear to me as soon as the speed ratio of 0.2

If one accepts that number roughly then the average modern 2 seater pre-rotated to 200RRPM could see 40mph on the ASI before a problem occurred. If you also accept that the same aircraft will likely "wheel balance" at 300RRPM and 60mph becomes an issue. The paradox comes when you see an aircraft seemingly take off in a normal fashion at a normal attitude but then suggest that it had rotor to tailplane contact - which can only occur with slow rotors and large backstick inputs [assuming design]. You don't strike the tail with a flat rotor....and if its too flat you don't get RRPM and neither do you get airborne.

Elsewhere a view was given on the inability to keep the stick fully back on a Magni... well thats not technique thats just arm strength!

 

[EI-GYRO]

Bensen figured this out years ago, Ken Brock agreed. Balance on the mains and you will automatically assume the correct correlation between
speed and rotor rpm, and will takeoff in the correct attitude.
It is proper gyro takeoff technique, not rocket science. (
Your mileage may vary with other methods, but is not likely to improve, as training by numbers has clearly demonstrated.

 

[Vance]

In order not to further derail this thread I will start a new thread in theory of flight, aerodynamics about my opinions on how a two blade semi-rigid rotor works.

 

[fara]

Rog. Just there seems to be an early view that focuses upon the take off and blade sailing/rotor/rudder contact but the unstick seems pretty clean in that film and usual blade sailing leads to disymetry of lift, rotors hitting teeter stops and a roll over. The aircraft doesn't seem unduly fast either. Just saying from what I can see...

Its always best to wait and allow all information to gather before forming a view. Early guesses are working theories usually and many of them go by the way side and many seemingly unbelievable things become believable. That's just how it goes in aviation. God knows I have experienced that in many investigations of airplanes, trikes (microlights) fatal or serious accidents. I don't see gyroplane accidents being anything special in that respect.

But just as an FYI, we know someone in the US who has managed to have a flap right at the start of the takeoff roll hitting the rudder, damaging (actually chopping off) its top hinge and continue to takeoff and fly for 10 minutes and come back and land and only once in taxiway he turned is when the rudder leaned over.
And he had 2 years later another flapping accident where he continued to roll and rotor kept hitting and flapping probably 5 times and finally he stopped as gyroplane started to lose directional control a bit. Never rolled over. Just FYI. May be he should quit while he is ahead before your prescription of a definite roll over comes true

 

[Philbennett]

I hear you fara with the profile of the recent gyroplane victims over the last 4-6 weeks the majority seem to fit the older and less experienced gyroplane pilot and as you say the unbelievable can become believable.

All that said this take off didn't cause his LOC. Important to state so that the less confident don't throw everything they know about their own flying in the bin. The examples you relate where you have issues at the start of a take off roll are just insufficient rotor RPM's which requires very little intelligence to remedy. Probably also worth stating that the loss of rudder authority doesn't need to lead to LOC.[of course talking about the Utah accident here]

On the Florida accident did you find more wx data? As seems weather related.

City of Palatka weather record shows 3 mile visibility with mist around that time. By 6 pm onwards Palatka city was listed as fogged in.

 

[ultracruiser41]

Bensen figured this out years ago, Ken Brock agreed. Balance on the mains and you will automatically assume the correct correlation between
speed and rotor rpm, and will takeoff in the correct attitude.
It is proper gyro takeoff technique, not rocket science. (
Your mileage may vary with other methods, but is not likely to improve, as training by numbers has clearly demonstrated.

Agree! You can’t balance on the mains....if the rotor is not loaded.....simple as that. I balance on the mains in whatever gyro I’m flying!

 

[anthom]

These accidents are really tragic. My sincere condolences to the family.

I am currently training students in three types of gyros. The open AR1, enclosed Eclipse and Magni M24. All three have their individual characteristics. I teach wheel balancing on both the tandems, but the M24 has a problem of the tail wheel making contact with the RW if the nose wheel is kept up for any length of time. So I do not teach wheel balancing on it.

The reason I teach wheel balancing is so that the student gets to use all the three controls appropriately before getting fully airborne. It also ensures that the rotors at the right flight RPM,

This particular crash is like many others, where no witnesses were involved. So we'll just have to wait for the Safety report.