Xenon Mast Failure

[OzGyro]

Hi All

Just found this on the Yanky forum, shall be very interesting as to what is the final outcome on this one.

http://www.rotaryforum.com/forum/showthread.php?t=26829

http://www.gyro24.com/forum/viewtopic.php?f=13&t=231

Cheers
Darren

[FLYNOTE]

Eina !!! If something like this happens we all jump like hell, throw a cat amongst the pigeons and start speculating on how good or bad the different constructions are. ! This also brings the materials that the machines are built in to the fore again.Chrome-alloy aeronautical 4130 steel, tig welded vs stainless steel, vs chrome alloy, stainless steel frames . Here is the factories report ;Text Celier Aviation

Hi everyone,

I appreciate the focusing on that. We got the full set of photos and report. Indeed, it is yes a low experience pilot typical error, with a very bad and strong blade flappping. The machine was on static. All of us know the potential kinetic energy stored in a rotor.
We feel sorry for the guy, but we are already getting organized to help him rebuilt the machine. This is a good point since the beginning with Xenons, it is always repairable. Our today statistics are i think the very best in the gyro world: 127 machines flying, 0 fatality, 0 injury... 100 RST (turbo Celier Aviation engines), not a single failure due to normal use and maintenance. Today is +30 000 hours cumulated on this turbo (by the way re-certified).
About the mast, i would like to remind all that we have passed the very strict certification in Poland, where physical testing is requested by independant laboratory. The mast holds exactly 10 500 kg of force traction including the back and cyclic force of the rotor, and the interaction with the fixation points to the cabin. It means you have around 21G force capacity at 500 kg total TO weight... Enough strong ??? And YES the mast is designed to brake at a special point right at the top of the cabin, above such an impact force, simply to protect the occupants. It did always work when necessary. A blade flapping, depending on the violence of change of rotor angle, the precession effect mixed with the gyroscopic effects CAN generate such forces and more...
The machine is not so badly damaged as some people here speculate, and according to the customer wishes, could be fixed in a matter of 5 days at our factory. Again this is the winning design of the Xenon, that will not let a broken bird on the side.
We therefore, encourage people to be taking their time to get a proper and quality training, to never rush for a take-off, to respect the machine and its limitations. Then we can all fly safe and in peace. Thanks for your attention.

Raphael Celier

[saraf]

First of all there is no factual information here. What we have is a sales pitch for the aircraft without a serous look at the failure. There are some numbers he quote which I question 500kgs or 1100LBS as a total take off weight is this really their max take off weight? The other number of 30,000 hours on the (Turbo) what is the total hours on the actual air frame? How many Aircraft are in the fleet? What is the highest number of flight hours on one Aircraft? And what were the flight perimeters during these hours? Was the take off weight less than the 1100 hundred pounds?

I also think that you should always consider if it is wise to have parts break off? This poises a greater risk to the pilots and innocent by standers. The usual is to have a progressive absorption of an impact through the controlled collapse of the components while they absorb as much of the load as possible without the total fracturing off of the component. Through design you hope that the metal components while twisting and bending are absorbing the shock and that within these components you have stronger items to prevent a total collapse unto the cabin, so that the out side components are taking the shock and are allowed to collapse to a point where it then stops bending and forms a roll bar, cage to protect the pilot and passenger. This of course is all to a point and some accidents are just not seviourable and these components will only do so much.

When we talk about the release of parts, do think about the rotor system and lets say you at a fly-in or air show you are getting ready for take off and you mess up on the prerotation, you start to have blade flapping and the air craft design releases this 28 foot rotor blade spinning at say 300 rpm out of control into the spectators along the run way. Or should the same thing happen and the air craft design starts to collapse, the aircraft rolls over, the blades are destroy yet still attached to the aircraft. The pilot and passenger are help out of the wreck and leave with their heads hung low because of and embarrassing mistake where the pilots ego repairs over time and the aircraft is rebuilt and put back into service with extra training for the pilot.

What works better for you?

And by the way mentioning all different types of metal don’t help with the actual investigation. It comes down to what happened? What fail during this incident? Was it a design failure yes or no? If the failure was not supposed to occur then look at the parts that fail and determine what needs to be done to accomplish the strength requirement it maybe a redesign of the entire unit.

And then again it may be and increased size of the part or a new stronger material .If you use a welded frame it is of no use talking about materials that can’t be welded. Don’t talk about its strength this is only a smoke screen to cover a design flaw. For instance aluminum has a very broad range of strength from 6061 @ 45,000 lbs/sq/in to 7075 @ 125,000lbs?sq/in however if you decide to weld these components and have a mechanical failure you may find the weld was not done properly so for us to say that this is the strength and compared to 4041 this is the strength and compared to 4130 or stainless steel this is the strength has nothing to do with the situation
So you have to look at the facts and decide for yourself.

Regards
Eben Snr

[Vertical Tango]

Raphael, please stop with your usual BS.
Please get a proper account from the pilot of his take-off run, i.e. altitude he was taking-off from, length of his rotor, pre-rotation RPM at the moment of starting his t/o run, full power immediately or progressive etc.... We are qualified enough then to decide if it was blade flapping or not.
For those not familiar with the Xenon, the mast still attached to the rotorhead on the picture is probably only half of its total length. The other half is probably still in the fuselage and it snapped as it protudes out of the top of the cabin. There is no particular point in the length of the mast where it is designed to break but logically it should occur where there is no fastening anymore. The cabin is very strong and where it occured in this case is very logical.
On the stats quoted, Raphael sells the RST and RT models. The only differences between the 2 are the engines. The RT is the standard 914 and the RST is a 912 with a non Rotax Turbo. The way Raphael explains makes everyone believe that he is the designer of the RST ("turbo Celier Aviation engines") which is not true. Hence the +30,000 Hrs mentioned are not in Xenons if they have been done at all by anyone in any aircraft.
Eben queried the weight of the machine: If I am not mistaken, in SA the Xenon is rated for 525 / 550 Kg depending on the length of the rotor and cheek plates at the rotorhead attachment. My Xenon has an empty weight of 306 Kgs. The difference is like always, for pax, fuel and luggage.
Why I have posted this note : I own a Xenon and I am satisfied with the design and its strength. Apart from the demo Xenon in SA, I am the only one who has built a Xenon here and I know how it is put together. However I get angry when Raphael is taking any opportunity to advertise how great he is and often twist figures instead of giving valuable and constructive comments on the subject in discussion. Basically he has missed an opportunity to shut up.

[t-bird]

Sorry I don’t understand how a blade flap without hitting anything could result in a mast breaking.

“A blade flapping, depending on the violence of change of rotor angle, the precession effect mixed with the gyroscopic effects CAN generate such forces and more...”

[mak]

Eben Snr

Just a few comments and to try and answer a few of your questions.

And by the way mentioning all different types of metal don’t help with the actual investigation. It comes down to what happened? What fail during this incident? Was it a design failure yes or no? If the failure was not supposed to occur then look at the parts that fail and determine what needs to be done to accomplish the strength requirement it maybe a redesign of the entire unit.

I agree 100%, the designer should not comment till after the investigation is complete and then rectify any problems if needed.

If you use a welded frame it is of no use talking about materials that can’t be welded.

Not sure what you mean by this, the mast is one continuos piece, there are no welds on the Xenon's mast or frame.

if you decide to weld these components and have a mechanical failure you may find the weld was not done properly so for us to say that this is the strength and compared to 4041 this is the strength and compared to 4130 or stainless steel this is the strength has nothing to do with the situation

Again, no welds, so the only determining factor as Raphael mentioned will be the type of material and obviously their strenght.

you start to have blade flapping and the air craft design releases this 28 foot rotor blade spinning at say 300 rpm out of control into the spectators along the run way.

I am not a very experienced pilot, but I have never heard of a blade flap @ 300RPM. Usually we start to fly @ 300RPM. Can a blade flap happen @ 300RPM??

Through design you hope that the metal components while twisting and bending are absorbing the shock and that within these components you have stronger items to prevent a total collapse unto the cabin, so that the out side components are taking the shock and are allowed to collapse to a point where it then stops bending and forms a roll bar, cage to protect the pilot and passenger.

I agree with you, just remember the cabin of the Xenon has a designer roll cage (strenght and shape) incorporated behind the seats right under the mast. The rotors would hit the ground and absorb most of the energy long before the gyro would roll over onto the roll cage. As can be seen from the photos, the rotors had a big impact with the ground. In most cases where rotors have a ground strike (especially during blade flap where rotor RPM is relatively low), only the one rotor have a lot of damage (as it is taking the most force of the rotor energy) and the second rotor blade a lot less damage as there is almost no energy left (I know my second blade was almost serviceable after a much highter RPM ground strike than a blade flap rotor RPM). I do believe the mast only seperated after the rotor blades struck the ground and absorbed all the energy and because of this force the mast broke (as Raphael said this as a "safety feature". He explained this to us on our visit to the factory when we collected our gyro, so I know it is not just a story he is making up now). In my laymans opinion, I can't see the mast break just due to a blade flap, but maybe due to a ground strike due to a blade flap.

I also believe that this rotor and mast, after taking most of the force and impact, then seperating, rolling and skidding along the ground won't have a more serious effect on bystanders than an uncontrollable gyro losing direction @ 50MPH and rolling and tumbling towards them.

The other number of 30,000 hours on the (Turbo) what is the total hours on the actual air frame?

The Turbo was only introduced +- 18 months ago and not all machines run on the turbo, so the airframe hours should be quite a bit more.

How many Aircraft are in the fleet?

The last time I heard, 107 were flying across the world.

What is the highest number of flight hours on one Aircraft?

I stand to be corrected, but this is close to 1000 hours.

And what were the flight perimeters during these hours? Was the take off weight less than the 1100 hundred pounds?

Don't have this info.

The one positive thing from this accident for me as Xenon owner: I haven't seen a gyro (in my limited flying years) not roll over during an uncontrolled blade flap. Normally they roll over and sometimes eventually tumble. I think the credit for this Xenon not rolling over must go to the mast seperation and the much wider wheel base of the Xenon.

Eben, as you said

What works better for you?

, either the mast and rotor coming off during accident and gyro staying upright or rolling and tumbling in gyro with rotor and mast in tact.

Preferably neither.

My laymans 2c worth

[Gyronaut]

I am not a very experienced pilot, but I have never heard of a blade flap @ 300RPM. Usually we start to fly @ 300RPM. Can a blade flap happen @ 300RPM??

You are right Mak, blade-flap happens when the advancing blade (into wind) "flies" while the retreating blade (with wind) stalls.

We know that a 10m rotor 'flies' at approx 110RPM (+120mph)

At 300RPM the tipspeed is + 350MPH - so unless you are standing on the ground in a 230MPH headwind the retreating blade won't stall - thus no blade-flap.

of praat ek alweer nonsense?