Fatal - AutoGyro MTOSport D-MTMZ, near Hildesheim airfield, Germany 21 JUL 2021

[Martin W.]

There is absolutely no reason a properly installed propeller blade will come out of the hub. The testing done for checking the clamping strength of the blades into the hub in Part 23 as well as in ASTM standard is way beyond what the propeller will ever see. However, no one can protect a user from themselves. If they over or under torque bolts, don't setup the pitch the same before torque, don't safety wire properly, use the same nylocks over and over again, don't use nordloc washers properly if applicable. All these things create potential failure points. Of course in this case it may be also delamination of the prop blades as well from a bird or FOD strike or from defect
BTW, I have heard of a few 2 blade wood props coming off just the same. No more, no less. Wood expands and contracts with change in heat and humidity and you have to maintain torque much more frequently. When they don't, out goes the prop

Thanks. I am curious what might happen to a prop if some cargo or heavy camera etc was to exit the cockpit and hit the prop of a pusher gyro . The only cases I am familiar with are helicopter tail rotors and were very destructive.

 

[knussear]

Seems unlikely - I fly the same machine - and have seen many like it. I have never seen one without rear mag switches.

Found another photo - and it looks like maybe it does NOT have mag switches in the rear. MTMZ photo

 

[Abid]

Found another photo - and it looks like maybe it does NOT have mag switches in the rear. MTMZ photo

That's crazy. Instruction w/o engine kill switch for the instructor. I'd never skip that

 

[gyroplanes]

Thanks. I am curious what might happen to a prop if some cargo or heavy camera etc was to exit the cockpit and hit the prop of a pusher gyro . The only cases I am familiar with are helicopter tail rotors and were very destructive.

I watched as something went through the prop of a Rotax powered trike. They managed to set down before the runway's end. A quick look showed a missing prop blade. The prop was an early model and the impact severed the hollow blade in two. The part of the blade went through the wing (sail?) and the engine auto quit when it almost left the mount and was hanging by wires, cables and hoses. Scratching their heads they were wondering why when the student said "Hey where's my goggles" The goggles were those seemingly one-piece green soft plastic with clear lenses worn over regular glasses often.
I rode my motorcycle down the runway and off-to-the-side I found whacked goggles and the missing blade fragment.
A lost prop blade occurred at Farringtons once. The prop was an early IVO with the "glued" on ring at the prop base grip.

 

[Resasi]

Found another photo - and it looks like maybe it does NOT have mag switches in the rear. MTMZ photo

How on earth can you tell from that photo?


Just one more reason I chose Warp Drive for my prop. They are seriously tough.

 

[Timothy Terbolt]

How on earth can you tell from that photo?

The MT-03/Sport normally have the rear-seat mag switches positioned behind the throttle - there are no switches present in that location in the photo. The aircraft also does not have a wheel brake in the rear seat for the instructor (there is no brake lever mounted on the throttle lever) , which would also suggest that it doesn't have much of an "instructor pack" fitted.

The earliest MT-03s had a stick and pedals for the rear seat, the rear throttle was an option. They didn't have a wheel brake or mag switches in the back. I recall that rear-seat mag switches were added as an option as they were a requirement for the UK market, they didn't appear to be a regulatory requirement in Germany at the time.

 

[knussear]

How on earth can you tell from that photo?


Just one more reason I chose Warp Drive for my prop. They are seriously tough.

They would be mounted right behind the rear throttle where the headset connector is sitting. Compare it to the white one in this photo with the same red gyro (D-MTMZ) where you can see the mag switches under the red protectors.

 

[Tyger]

That's crazy. Instruction w/o engine kill switch for the instructor. I'd never skip that

Interesting. There's no back-seat engine kill on my M-16, nor was there on any of my instructors', IIRC. The potential need for one did not occur to me before now.

 

[Resasi]

As a remote ie placed some way from the student, it does become important...as an unfortunate Instructor of mine found out when I had inadvertently left the mixture lever in the wrong position and he was in the back as the engine was sounding rather poorly right after TO.

Luckily he is a calm and thoughtful man, his instruction/queries/exclamations were intelligible and all was resolved before the situation became too uncomfortable.

Bring any memories Vance?

A memorable ride, a memorable gyro, to my mind the Dreadnought of Gyros. She’s a Queen Vance. Sweet, responsive and honest. Loved every minute...but there was an instance where the instructor was not in control of the situation.

As for the accident victims my heart goes out to them both.

 

[Kevin_Richey]

Does anyone else recall seeing a photo in any links to this accident of a prop hub w/ three sheared-off prop blade roots?
I thought I'd looked @ a photo that I'd enlarged, but cannot find it on any of the news links now being shown....

 

[Kevin_Richey]

That hub bar clamp that Autogyro uses appears to be undamaged. Just as if the rotor was cleanly cut off @ that end.

 

[Abid]

Interesting. There's no back-seat engine kill on my M-16, nor was there on any of my instructors', IIRC. The potential need for one did not occur to me before now.

Brakes fail for instance. The instructor needs to be able to immediately shut the engine down. Student applies sudden power overpowering the instructor and many other scenarios. I have my engine kill switch guard up every time a student starts the gyroplane

 

[SARAF]

Blade section attached to aircraft

 

[DASBUR]

Blade section attached to aircraft

In the helicopter world we determined 20 years ago that extruded rotor blades were not the best choice. Back then the extruders were not able to extrude that thin of a profile in anything other than 6063. Not sure if that has changed or not. It was discussed here a while back someone was having a fretting problem with extruded blades between the aluminum spacer blocks and the blade. I remember thinking at that time that this setup was not the best. About a week ago I saw a video of someone assembling blades that looked like the one in the picture. they were greasing the surfaces of the spacers.. I assumed that that was done to stop the fretting. I think a better way for a root attachment would have been a solid spacer with full contact to the blade bonded to the blade with a doubler system to distribute the bending load more evenly through the root of the blade. The last bolt there was a shear point. There is a lot more bending and flexing going on with blades than you think.

Doug

Just my uneducated opinion

 

[Brian Jackson]

In the helicopter world we determined 20 years ago that extruded rotor blades were not the best choice. Back then the extruders were not able to extrude that thin of a profile in anything other than 6063. Not sure if that has changed or not. It was discussed here a while back someone was having a fretting problem with extruded blades between the aluminum spacer blocks and the blade. I remember thinking at that time that this setup was not the best. About a week ago I saw a video of someone assembling blades that looked like the one in the picture. they were greasing the surfaces of the spacers.. I assumed that that was done to stop the fretting. I think a better way for a root attachment would have been a solid spacer with full contact to the blade bonded to the blade with a doubler system to distribute the bending load more evenly through the root of the blade. The last bolt there was a shear point. There is a lot more bending and flexing going on with blades than you think.

Doug

Just my uneducated opinion

Do helicopter rotors experience firing pulses the way a propeller does? Or does the transmission tend to smooth out that wave pattern?

 

[Abid]

In the helicopter world we determined 20 years ago that extruded rotor blades were not the best choice. Back then the extruders were not able to extrude that thin of a profile in anything other than 6063. Not sure if that has changed or not. It was discussed here a while back someone was having a fretting problem with extruded blades between the aluminum spacer blocks and the blade. I remember thinking at that time that this setup was not the best. About a week ago I saw a video of someone assembling blades that looked like the one in the picture. they were greasing the surfaces of the spacers.. I assumed that that was done to stop the fretting. I think a better way for a root attachment would have been a solid spacer with full contact to the blade bonded to the blade with a doubler system to distribute the bending load more evenly through the root of the blade. The last bolt there was a shear point. There is a lot more bending and flexing going on with blades than you think.

Doug

Just my uneducated opinion

Helicopter rotors have to deal with huge power pulses. Apples and Oranges and really not relevant. And this accident I highly doubt has anything to do with extruded rotors. We have seen composite rotors throw apart and kill people as well on gyroplanes and it all depends on design and construction method of specific rotors.
This problem has happened before on AutoGyro rotors in 2011. They came out with rotor system 2 as a result and somehow set their life to 2400 hours when rotor system 1 had trouble at 700 hours. I asked Averso how can they set the time to 2400 hours. Averso's answer to me was if AutoGyro rotors can be set to 2400 hours, theirs would be to 3000 hours but they don't believe it is dealing with reality. Their clamping plate design is different and a bit strange in my opinion. It does not touch through the whole blade surface and creates a potential flexure point for the blade. Why? I never understood that. I am guessing this is rotor system 2 on this machine.

 

[Abid]

Blade section attached to aircraft

Is this from this particular accident machine or is it from rotor system 2. I hate the fact that the clamping plates do not touch the whole surface contour of the blade. To me that's really strange. Anyway without more factual data all I can say is that rust on the bolt shows it really was not maintained or inspected at regular intervals. That did not happen overnight unless these took a drink in salt water.

 

[Kevin_Richey]

Blade section attached to aircraft

The beginnings of that rust should have been caught years ago if the rotorblade attachment bolts had been removed & inspected regularly...although the rust likely did not cause the rotorblade to detach from that point. Regular inspection might have caught a crack developing there. The missing from the accident scene broken-off rotorblade photos ought to be equally horrific.

I shudder to see photos of departed rotorblades, because 15+ years ago, Jim Vanek was emphatically telling us in PRA Chapter 73 that extruded rotorblades aren't strong enough because of insufficient strength of 6063 architectural-grade aluminum that is extruded (screen doors & railings stuff).

He added that we would hear about extruded blades coming apart IN FLIGHT because they do not have the necessary strength/margin of safety for flying, & that it had already happened, but has been kept quiet. Criminal for those who did so.

 

[Abid]

The beginnings of that rust should have been caught years ago if the rotorblade attachment bolts had been removed & inspected regularly...although the rust likely did not cause the rotorblade to detach from that point. Regular inspection might have caught a crack developing there. The missing from the accident scene broken-off rotorblade photos ought to be equally horrific.

I shudder to see photos of departed rotorblades , because 15+ years ago, Jim Vanek was emphatically telling us in PRA Chapter 73 that extruded rotorblades aren't strong enough because of insufficient strength of 6063 architectural-grade aluminum that is extruded (screen doors & railings stuff).

He added that we would hear about extruded blades coming apart IN FLIGHT because they do not have the necessary strength/margin of safety for flying, & that it had already happened, but has been kept quiet. Criminal for those who did so.

Why do extruded rotor have to be 6063 Aluminum? Is that a rule or something or just a generalization? Averso rotors are not 6063. Are AutoGyro blade extrusions 6063? We unfortunately have also heard of fatalities with carbon fiber rotors. There is a lot bigger human factor in composite or bonded rotors relative to a process like extrusion. It just depends on design and quality control.

 

[Kevin_Richey]

I pointed out that 6063 was used years ago when we first started to hear of extruded aluminum rotors. I have no idea what Autogyro of Germany uses in their construction/extruded process.

What # of aluminum are Averso rotorblades, Fara?
The only failures (fatalities) I have heard of from carbon fiber construction have been of the balance rod of one rotorblade being flung out in flight (w/ horrible results to the pilots & passengers & their families), and not from breaking apart in flight.

But, I'm not on the insider knowledge track of rotorblade failures worldwide, as the gyroplane & rotorblade manufacturers are...as well as those w/ access to photos showing all of this not shown to the public.

I do know that this thread on our forum from a couple of yrs. ago delved extensively into crystallined aluminum (likely from being work-hardened) & rotorblades breaking off @ the point where the last outboard bolt held the rotors to the hub bar:

https://www.rotaryforum.com/threads/another-look-at-the-autogyro-mtosport-crash-of-11-september-2016-in-germany-d-mdoz.1143796/

If one reads that thread casting away the personality clashes between CFIs & other gyro flyers, it is chilling to compare previous rotorblade departures from the hub bar, whether catastrophic collisions w/ Mother Earth, or merely mild tip-overs while taxiing or slightly airborne impacts in ground effect.

I haven't heard in the 30+ years I've been involved in gyroplanes of ANY Skywheels, or Dragon Wings nor Sport Rotors having the hub bars or rotorblades depart in flight from material failure. I would expect that Denis Shoemaker's new aluminum Razor Blades to have the same robustness, since they appear to utilize the same material & construction process as DWs & SRs.