Can anyone share some thoughts with this guy's

[SARAF]

Re: Xenon Gyro
by FlyingDoc » Wed Mar 30, 2011 3:39 pm

If it wasn't for the integrity of the Xenon cabin, and the four point harness, I don't think I would be writing this!

What happened! Pre-rotated to my normal 250-270 RPM with the engine at 2500 RPM. I had switched off the solenoid at 90 RPM ( my normal practice.) pushed the Pre-rotator lever forward, pulled the stick all the way back, and applied engine to 4000, checking that the rotor RPM came up again to 270, increased engine power to 4400, nose came up, held nose and increased power, then noted an "unusual" vibration! ( this was not an engine, or rotor vibration, nor a wheel one) I was just considering pulling power, when the craft lifted off the ground, and then "all he'll broke loose!!".

The rotor struck the ground on the left, then we ( myself and my trusty Xenon) proceeded to tumble down the runway, we tumbled four times (I suppose 3,5 times) as we came to rest upside down! Still in the harness I was able to push the button, fall to the ground (roof) and proceeded to exit the craft asap!!
I should point out the weather was clear with a 5 - 10 kph crosswind from the south, I was using 08.

As I said, besides a small cut on my left thumb, I am fine, ( other than the fact that my craft is a pile of composite and aluminum)
(tried to attach an image but having hassles with the iPad)
Alan



Posts: 56
Joined: Fri Feb 15, 2008 9:58 am
Location:

[RotorTom]

Blade flap.

[SARAF]

I doubt it

"quote"

What happened! Pre-rotated to my normal 250-270 RPM with the engine at 2500 RPM. I had switched off the solenoid at 90 RPM ( my normal practice.) pushed the Pre-rotator lever forward, pulled the stick all the way back, and applied engine to 4000, checking that the rotor RPM came up again to 270, increased engine power to 4400, nose came up

[birdy]

I doubt it

If he did have the said RRPM then i dout it too, but im thinkn he didnt, and flaped the blades.
Why else would it shake like hell then strike the ground on the left side?

[Fl90]

definately sounds like flap.

[SARAF]

then noted an "unusual" vibration! ( this was not an engine, or rotor vibration, nor a wheel one

[helicopter ed]

This unfortunate happening baffles me a bit. For nosewheel to come up, your rotor was ready to fly, and 250 to 270 increase to 300+ very quickly when loaded with power and speed. It definitely rolled left and that is a definite low rotor RPM problem. I taught all my hundreds of students to watch the rotor, not the tach. When you cannot see a blade, and it is a round disc, Go for it, it will never flap. Sorry for your loss. I have been through it. My best friend mid aired me. and lost him. and two beautiful flying machines. I was lucky, You were lucky. Count your blessings...

[Chuck Roberg]

Need a little more information. Such as is the mast still intact or did it break free.

[PTKay]

Pre-rotated to my normal 250-270 RPM with the engine at 2500 RPM.
As a fresh Xenon trainee I would say it is not possible
to get 270 rpm on the rotor with 2500 rpm on the prop.
But maybe it is a different prerotator installed on this machine.

I would bet for rotor tachometer failure (false positive readings)
and subsequent blade flap.

For nose wheel to come up, your rotor was ready to fly,

To lift the front wheel in the xenon 120-150 rpm on the rotor is enough,
when you keep the stick full back.

On the ground you need not more than 5kg force to lift the nose by hand.

But I trained on the newest version with the flexible prerotator shaft.

[BEN S]

ST1100 motorcycle, I looked down at the cluster and it said I was going 55, so as I was on the highway, I increased my speed to 65. Problem was I was zipping by people so fast I couldn't read a license plate number! It turned out I was looking at the tach NOT the speedo. (doing 130mph by the time I figured it out!)
What is the pilots experience with this machine? Are the numbers accurate? Why would he know them? I was taught to fly the machine not the numbers, I don't even have a rotor tach. If I did I wouldn't be watching it anyway.
Too bad about the rig.
Ben S

[Passin' Thru]

Assuming the numbers are correct, It sounds like all was well before forward movement. The problem occured during forward acceleration.

Assuming blades turn to left as viewed from below.

Initial autorotation is achieved as machine tilts back.

Great viberation experienced during forward acceleration.

Advancing blade takes the lift but teeter seizure prevents eqalization.

Disc rolls into retreating blade until stricking ground.

Without further information, That would be my deduction.

The centrifugal blade teeter locks failing to release could cause cause such a scenario .
After further consideration, I suspect the locks to be the most likely suspect.

[PTKay]

The centrifugal blade teeter locks failing to release could cause cause such a scenario .
After further consideration, I suspect the locks to be the most likely suspect.
There are no locks on Xenon rotor.

Of course, the rotor could have been replaced for another type.

When delivered, it didn't have them.

And yes, the prerotator is the old type.

http://www.microlighters.co.za/download/file.php?id=7665&sid=669371a07f20a72e8f8291193dafbc2e

[Passin' Thru]

[QUOTE=PTKay;414752]There are no locks on Xenon rotor.

Of course, the rotor could have been replaced for another type.

When delivered, it didn't have them.

And yes, the prerotator is the old type.

[QUOTE]

Interesting ... I thought I remembered it having them, My bad.

It certainly seems like something interfered with blades' advancing - retreating lift equalization.

[willisbr]

There's a big difference in reacting and considering. You can't do both at the same time. An unusual vibration should have been met with a reaction to pull the throttle immedtiately. A consideration sounds a bit too late whether the aircraft rotated or not.

[Gyro_Kai]

If I remember correctly, then flying RRPM is more in the vicinity of 350 for one person. Paul, what do you say?
Of course the blades could be longer, there are several blades sizes available.


Kai.

[PTKay]

We were flying 350-360 RRPM level.
400 hard bank.

[Steve_UK]

Hi



*If* the machine in question is the machine shown in the above photo then this would be a 914 Turbo powered example - very few have this engine.


I am *not* suggesting this had anything to do with the incident, just trying to add a little more potential insight.

Regards


Steve

[PW_Plack]

...then noted an "unusual" vibration! ( this was not an engine, or rotor vibration, nor a wheel one

With all due respect, it is not possible to say definitively what a vibration was not caused by, until you have proven definitively what it was caused by.

If this pilot claims to have ruled out the wheels, engine and rotor, what is left to vibrate? Would it be safe to assume a Xenon is not prone to aerodynamic flutter at takeoff speeds?

If the rotor hit the ground before the entire machine started rolling, then what are the possibilities other than blade flap or mast failure? Those possibilities would have to account for enough force to drive the rotor into the ground.

[PW_Plack]

As a fresh Xenon trainee I would say it is not possible
to get 270 rpm on the rotor with 2500 rpm on the prop...

On the ground you need not more than 5kg force to lift the nose by hand...

Paul, 2500 RPM on the prop with a 914 (2.27 ratio?) is 5,675 engine RPM, close to engine redline. If it's possible at all to prerotate to 270 rotor RPM, it should be possible at full power.

As far as lifting the nosewheel with 5 kg force, it sounds like you tried it with nobody in the cockpit. If there was only 5 kg on the nosewheel with a pilot in place, the machine would sit on its tail when empty.

[PTKay]

Paul, 2500 RPM on the prop with a 914 (2.27 ratio?) is 5,675 engine RPM, close to engine redline. If it's possible at all to prerotate to 270 rotor RPM, it should be possible at full power.

PW, my mistake. Sorry.

For me from my Lycoming experience prop RPM=engine RPM :(

What happened! Pre-rotated to my normal 250-270 RPM with the engine at 2500 RPM.

In the original post, as quoted above, it says clearly engine 2500 RPM.
At this power I could hardly reach 150 RRPM before tilting the rotor
back, taking advantage of prop wash and reving the engine up.
Only then I got about 270 on the RTS engine and started rolling.

I just checked the manual for RST I am flying,

You start prerotation at 1800 engine RPM and increase gradually
the lever until you reach 150 RRPM, ten tilt back and start reving up.
It says you should reach 280 RRPM at 3000 RPM.
If the gears are the same, it would mean app. 220 RRPM at 2500 RPM.

But I repeat, it is a different machine.

[Fl90]

you can get a machine off the ground before the rotor is ready.....and the description was what it feels like.

[PTKay]

As far as lifting the nosewheel with 5 kg force, it sounds like you tried it with nobody in the cockpit. If there was only 5 kg on the nosewheel with a pilot in place, the machine would sit on its tail when empty.

PW, of course, my mistake again.

Nevertheless, with the rotor at 270 RPM I had to tilt rotor forward
when still on brakes to keep the nose wheel down.

[MAK]

We are all still in the dark about the cause of this accident. I will update you all if I receive any further information. The mast did break (just above the cabin) during the rolling and laid about 30 metres from the craft with the rotor still attached. The pilot was experienced and had a lot of hours on his Xenon and I tend to trust the figures he quoted.
My Xenon gets airbone @ 300RRPM. The best take off technique for me is hitting 60Mph @ 300RRPM, then the Xenon fly itself away from the ground, no roll to the right (We fly from the right). Only after take-off does the RRPM increase to 350. Obviously this happens quickly.
I know a blade flap sometimes feel that you are getting airborne and the next moment you are being flipped over, but I don't think the nose of the Xenon would have lifted if the RRPM was low.
We pre-rotate to +- 180 RRPM and then apply power and the nose only lifts @ about 250 RPM with the stick full back.
The aircraft having rolled 3 or 4 times doesn't look good and we are gratefull that he got out without a scratch. A nice testimony for the strenght of the Xenon cabin that are still fairly in tact.

Eben ek sal jou op hoogte bring as ek iets meer weet.:yo::yo:

[PTKay]

I checked the manual again and found an interesting warning:

When the machine is not properly loaded (flying solo) do not prerotate over 200 RRPM
to avoid the risk of loosing control on the ground.

At the moment I have nobody to ask for explanation, but I certainly felt
the "weight" of the rotor on the stick and every little move was causing
unintended jerks of the cabin.

But there were two of us giving a proper mass to the machine
and Raphael was correcting my every mistake.

[PTKay]

you can get a machine off the ground before the rotor is ready.....and the description was what it feels like.

So, it would support the theory of wrong (too high) RRPM readings?

[Fl90]

I don't know about readings. A tach is something to look at, but I trust my butt more.

[Resasi]

Sorry to hear about this accident, glad that you got out OK.

I can say that I am grateful for finishing my training on a bare bones machine with no RRPM indicator and no prerotator. Learning rotor control by blade sight pattern and feel has certainly made me feel safer.

It does not however cope with component failure, which still could be a possibility in this case.

[birdy]

( this was not an engine, or rotor vibration, nor a wheel one
The stick wont move during blade flap if its on the stopper.
He said he felt a vibe, but reconed it wasnt engine [ too low a frequency maybe] wasnt a trye and he thought it wasnt blade vibes, coz the stick wasnt moveing.
It cant wen its on the same stop the blades are tryn to force it past.

[Passin' Thru]

( this was not an engine, or rotor vibration, nor a wheel one
The stick wont move during blade flap if its on the stopper.
He said he felt a vibe, but reconed it wasnt engine [ too low a frequency maybe] wasnt a trye and he thought it wasnt blade vibes, coz the stick wasnt moveing.
It cant wen its on the same stop the blades are tryn to force it past.

Those were my reasonings for suspecting the flopper stoppers, but they say the Xenon don't have flopper stoppers?:noidea:
If he had forced it off with the blades too slow, the stick would have been violent shaking, same if he had out run the blades. If the info he gave is accurate, I am back to thinking something was interfering with the teeter movement.
Perhaps we'll hear more later.

BTW: Cierva's first gyro had no provisions for teetering, or advancing - retreating blade lift differiential and it rolled over exactly as this one is discribed.

[bones]

Im learning lots here, i only got about 400hrs in one but man this is good stuff :)

[Dmorris]

Maybe I'm overlooking something but where is this gyro located and who is the owner/pilot?

I have the same pre-rotator and I start my takeoff roll at 200 RRPM's. Don't think mine would go much past 200 at 2500 RPM. I can get approx. 225 RRPM at 3000 RPM's but seldom ever push it past 200.

[Steve_UK]

The accident was is South Africa - the registration was ZU-EXU - the factory construction number is

CAI 030 70T - ie Xenon #030 built circa 2007

Is your machine of a similar age ?


Steve

http://xenongyroblog.blogspot.com/

[Steve_UK]

Hi Dave

Appears yours is similar - a 914 Turbo Xenon too, Xenon #038 from November 2007.

Regards


Steve

http://xenongyroblog.blogspot.com/

Steve

[Dmorris]

Steve,

You are correct I took delivery of mine January 2008 and it has a Rotax 914.

[birdy]

If he had forced it off with the blades too slow, the stick would have been violent shaking,
Pete, the stick cant shake if its already on the stop, but the blades will make the machine shake.

[Passin' Thru]

If he had forced it off with the blades too slow, the stick would have been violent shaking,
Pete, the stick cant shake if its already on the stop, but the blades will make the machine shake.
True, but what I'm saying is IF it wasn't the stoppers and he forced it, Then the stick would be beating him.

[birdy]

Fair enuf Pete.
Thinkn these quite a few holes in ol mates 'testemony'.

[Fl90]

one thing about it, the machine is wrecked. If the pilot doesn't know why, or isn't honest with himself.....it won't be the last time.

[MAK]

I have posted my coments a while back but for some reasons the moderators are not allowing my post.
I saw the pictures of this accident and the mast did come off during the rolling of the gyro and was about 40m from the gyro after the accident with the rotors still attached. Mast broke just above the cabin as can be expected during a roll. The accident is a real testimony to the structural strenght of the Xenon and the fact that it didn't catch fire like a lot of the accidents we had lately in South Africa.
It is an experienced pilot and he bought one of the first Xenons in South Africa and has been flying it for a couple of years and I would trust the information he provided.
The cause of the accident is a mystery to us all and I will inform everyone as soon as we have more information.
The Xenon starts to fly at 300RRPM and only picks up to 350RRPM once airborne. I know if you have a blade flap it feels as if you start to fly and the next moment roll over. I dont think the Xenon's front wheel will lift at take off if the Rotor RPM is too low as this pilot has explained his experienced. Only once at about 250 to 270 RPM does the front wheel of the Xenon lifts, not before.

[PTKay]

I have the same pre-rotator and I start my takeoff roll at 200 RRPM's. Don't think mine would go much past 200 at 2500 RPM. I can get approx. 225 RRPM at 3000 RPM's but seldom ever push it past 200.

Dave, exactly my observations here,
in agreement with the manual.
one thing about it, the machine is wrecked. If the pilot doesn't know why, or isn't honest with himself.....it won't be the last time.
In the interest of all of us flying, all the educated speculations
and every way of explaining, what really happened,
is sincerely welcomed.

[RotorTom]

Assuming he is totally accurate in his description ... the only other thing that occurs to me is that the mast could have failed. The mast support brackets on the older machines had a tenancy to crack. Most of us have replaced them.

[MAK]

One of the leading instructors in South Africa discussed this with the owner and this his words:

"I hate speculating but I think Alan and I agree that he fell victim to the dreaded 'High Speed Blade Flap'."

He also continue to discuss the dangers of take off in the new age side-by-side gyro's on our local forum:
http://www.microlighters.co.za/viewtopic.php?f=20&t=15604

It is scary to me that something like this can happen to an experienced Xenon pilot.

[birdy]

He's pretty close to the money, cept for this bit,
I have often heard pilots say that the wind must have thrown them over on takeoff. The wing tip speed (lift generating portion) of a typical rotor is in the region of 650km/h or 400mph at typical flight speed. A cross-wind of at least this speed will be required to throw it over. Anything less will push the gyro off course downwind but will not flip it over - or am I wrong here?

And he's one of your leadn instructers???

[willisbr]

A forward push on the rotors can unload them when trying to keep the nosewheel down. But we all do this. Even when balancing on the mains. I suspect a good push forward could screw you up. Two things I do: apply power gradually so my nose doesn't pop up abruptly and need to be slammed back down with a hard forward, and keeping bladed loaded while keeping nose lightly and the ground. It's gotta be smooth. This isn't a new phenomenon.

[willisbr]

What I mean above is we all balance on mains or keep nose wheel down while gaining airspeed. A push forward can unload rotors. We see rotor rpm decay by pushing stick forward on full stop. Forward stick and a slammed throttle could kill your rotor rpm and pop!

[MAK]

He's pretty close to the money, cept for this bit,
I have often heard pilots say that the wind must have thrown them over on takeoff. The wing tip speed (lift generating portion) of a typical rotor is in the region of 650km/h or 400mph at typical flight speed. A cross-wind of at least this speed will be required to throw it over. Anything less will push the gyro off course downwind but will not flip it over - or am I wrong here?

And he's one of your leadn instructers???

Birdy

Remember he is talking of the moment just before lift off, not if you are standing still with your rotor turning and not angled into the wind scenario.
Perhaps then you can answer the question that I have also been wondering. If you take-off and the moment just before you rotate, say 50-55Mph and RRPM just below 300, say 290RPM (Rotor tip @ 300Mph), what sort of a cross wind is required to blow you over, not make you drift off centre line, but actually blow you over?

willisbr

I am of the opinion that once the front wheel came up and as long as you keep it in the air and not push it back onto the runway (even with stick forward to just balance it on the main wheels) firstly there are no risk of unloading the rotor and secondly it is safe to apply full power. The key for me has always been that once the the front wheel has come up it must stay off the ground at all times to ensure positive rotor RPM. Am I wrong here in assuming that this is a fail safe method to avoid a blade flap?

[Fl90]

I find it odd that all the information is given on rrpm and engine speed yet no indicated speed is given. If all this happened at 20-40 kph or at 60-80 kph, makes quite a bit of difference.

Also, the technique used makes a difference. If a short/soft field take off, to get it off the ground then level the craft till desired climb speed. Or, a long run out so you're coming off the ground at trimmed speed.

[willisbr]

Mak every aircraft and configuration is different. For instane, in an RAF flying dual...since that's what we have been talking about (side by side enclosed), the nose is lightly placed back on the ground until 55-60 then rotate. Lightly. It's not a go cart. Don't need a firm plant on the ground. What I meant earlier is don't flatten the disk. Full back to putting the nose wheel back down lightly is just a few degrees. Ive seen a few videos of how people are taking off in xenon. Either it was a pilot thing or maybe or all xenon. But I've seen them prerotate and then slam the stik back as they apply full power. The nose pops up immediately and then he pushes the stick forward. This immediate back and forth must not be a good thing in my opinion. If this is the intended procedure, I again suspect that pulling back and then reacting to the nose by pushing the stick forward without a load may unload them and flap them. Sort of like a PPO but on the ground.

[birdy]

Remember he is talking of the moment just before lift off, not if you are standing still with your rotor turning and not angled into the wind scenario.
MAK, you can flap blades at any ground speed. From 0 to TO speed.
If the RRPM isnt up to the airflow, theyll flap.
But theres much more chance of loosen it at speed.


If you take-off and the moment just before you rotate, say 50-55Mph and RRPM just below 300, say 290RPM (Rotor tip @ 300Mph), what sort of a cross wind is required to blow you over, not make you drift off centre line, but actually blow you over?
If you dont stick into the side gust, it wont take much at all. Im not go'n to put a number onit, but it can be much less than your cruise speed.
If your in the situation you described, and a gust of bout 20 kts hits you from the side, the airflow the rotor sees is comen from that side, so the teetering action changes orientation to accomidate. IOW, the side of the disc that the xwind is hitn gets higher, allown more air under it and changen the teetering orientation further till the RTV is pulln the machine over to the side. All you gota do is stick into it and its a non event, just like a FW.
I know a 20kt breeze under the nose of the WASAs rotor at standstill with me sitn init and idleing [ 914]is enuf to push the machine backwards. So if theres enuf lift from just a 20kt breeze to do that, it wouldnt take much more from the side, uncorrected, to tip one over on TO.
Most of my TO rolls are no wider than the mains, with shrubbery under the rotors, so iv got to keep it streight, xwind or not.
And you cant keep it streight if you dont 'fly' it streight on the TO roll. [ stick n rudder]

As for the nose popn up, theres alota variation in the positioning of the mains in relation to the COM.
And every 2seater has the added difference of big changes with n without a passenger, so the nose is go'n to come up at greatly vairying speeds.
You cant hava blanket ruel that says if the rotors are lifting the nose off, its ready for full power.
Thats how it should be, but sum mains are so far forward it takes buggerall to lift the nose up, and the rotors may not have the rpm yet for full power.
Keepn the nose wheel off will give you the best RRPM gain, but just coz its off dont mean they are ready.
The standard RAF main position is too far forward.
One big bloke or two up will add weight to the nose, but your not far from flapn blades ina stock RAF if you got to WOT soon as the nose pops up.

[t-bird]

Is this not the second Xenon accident where the mast broke off after blade flap ?

[MAK]

Birdy

Perhaps you don't understand what I am getting at and you are just stating the obvious re xwind and rotor management.

What we are referrring to is often you hear a gyro pilot say after a roll over that everything was normal, he was tracking centre line (so obviously he was angling his rotor in the wind and compensating with his rudder), he got airborne and the next moment he rolled over. His comments afterwards is it was a huge wind that blew him over and the poor guy is not even aware that he had a blade flap.
What we are saying is from that perfect take-off setup of tracking centre line by compensating for the wind it must be a huge wind/gust to blow you over.

On the take-off procedure/rotor & power management I am talking Xenon specific (I think the M24 is the same). I know the RAF has its own technique and procedures.

As most of us here in South Africa are trained on machines with good pre-rotators (almost everyone pre-rotate to at least 180RPM) we know that we have our shortcomings on rotor management during take-off and might not be aware / manage it as well as someone that got his training on a machine that can only pre-rotate to say 100RPM.

t-bird

From the photos of this accident it is more likely that the mast broke off during the rolling of the gyro, not because of the blade flap.

[t-bird]

Or the Gyro started to roll because the mast started seperating and broke off when it hit the ground ?

[bones]

Or the Gyro started to roll because the mast started seperating and broke off when it hit the ground ?

Think about it, if the mast separated wouldnt it just leave the machine, if it broke i doubt it would pull a machine over, especially if he was in the air

[MAK]

t-bird

If you know the Xenon mast construction / attachment and seen the photo of the broken mast you would understand.

[t-bird]

Sound like a similar accident

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

[Steve_UK]

Hi

The German BFU accident summary says the following in a brief summary document ref
BFU RX004-10


From:
German
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Event:
Disorder without injuries
Date, Time
31.07.2010, 11:09:00 Clock (local)
City, State:
Freiburg, Germany
Damage to Aircraft:
Slightly damaged
Source: Source:
Application Number:
BFU RX004-10
During acceleration, the rotor began to beat and the rotor mast broke off.
Aircraft: Aircraft:
Structural Screws 0 bis 2250 kg

Pattern:
Celie Aviation - Xenon 2 '
Crew Crew
0 0
0 0
0 0
Passengers
0 0
0 0
0 0
Mode: Mode:
General Aviation - education - training
tion - Other Flight


Steve

[JetRanger]

If the mast separated and the rotor came off at full throttle, and the machine rolled over (which the German one didn't a.f.a.I.k), surely it would roll over onto the right hand side assuming that the prop turns anticlockwise as it does on most pusher-types. Why would the rotor and machine end up on its left side - or are you suggesting a partial break which pulled the machine over then seperated? :noidea: ...somehow don't think so.

[bones]

If the mast separated and the rotor came off at full throttle, and the machine rolled over (which the German one didn't a.f.a.I.k), surely it would roll over onto the right hand side assuming that the prop turns anticlockwise as it does on most pusher-types. Why would the rotor and machine end up on its left side - or are you suggesting a partial break which pulled the machine over then seperated? :noidea: ...somehow don't think so.

If partail separation, if the top of the mast went to the left, what would happen to the right push rod? it would get shorter, wouldnt it, and by doing that it would be pulling the rotor to the right, so if anything it would cancel out everything, and then it would tear off over the back

[birdy]

Perhaps you don't understand what I am getting at and you are just stating the obvious re xwind and rotor management.
Obviously i dont get wot your sayn MAK. :(

If your already off the ground [ just left it] and are powering upwards, and you suddenly get tiped over sideways,........ hell, im buggered if i can figure wot you [he] did rong.

Iv been 'traped' ina mountain valley for 20 mins, in VERY unpleasant conditions.
A strong SEer [ 5o kts and up] was blown over the north/south valley, and the turbulance was crazy. Watchn the vegitation for clues of wind direction i could see out one side trees standn calm as, out the other they were be'n striped of limbs, so it was impossable to read/predict flow, and with gusts as sort n hard as this, you can imagine how hard it was to stay in control. Full backstick, full forward, WOT, idle and everythn in between, but never once did i feel i was loosen control. Never came close to be'n inverted.
All im sayn i gess, is that if you dont correct, your go'n in, simple.

[birdy]

BTW, in your post 46, you said;
Remember he is talking of the moment just before lift off, not if you are standing still with your rotor turning and not angled into the wind scenario.
On the ground or off it, the result is the same, only the impact intensity will change.

[bopflyer]

"Is this not the second Xenon accident where the mast broke off after blade flap ? "

Hi all, around eight weeks ago a Xenon here in New Zealand had its mast ripped out and tail damaged when the pilot encountered blade flap while backtracking after landing to do another takeoff. Sorry but thats all the details I know.

[PTKay]

"Is this not the second Xenon accident where the mast broke off after blade flap ? "

Hi all, around eight weeks ago a Xenon here in New Zealand had its mast ripped out and tail damaged when the pilot encountered blade flap while backtracking after landing to do another takeoff. Sorry but thats all the details I know.

So it looks like Xenon is prone to blade flapping as any other gyrocopter,
needs attention while taxiing and on take-off, but generally will not
flip over or slice the pilot with the rotor, but rather get rid of the
mast and stay still standing on the ground.

In such taxi flapping incidents other gyrocopters usually flip over with all
the nasty consequences.

[Master Roda]

The mast seperating from the aircraft is not good no matter how you look at it.
If it was actually designed this way then I don't agree with it...AT ALL.
The blades can walk around and go through the cab if the mast becomes detached.
This is like a motor mount detaching and the prop going through the cab (happened before).
"other" gyrocopters are generally open cockpit. That's bad in any roll over. enclosed gyrocopters are typically strong enough to hold up to a roll over. They are not however able to withstand a heavy impact.....none are. The occupents usually don't survive anyway.

Make sure your mast is attached with proper hardware....look for cracks in the mast or brackets,etc. Many fixes have been made to several different aircraft because of this.

Please pre-flight your aircraft every time you fly. You may catch something before it becomes catastrophic. I have.

Jon

[Master Roda]

I forgot to mention.

A worse event would be the mast or rotors detaching and hitting innocent people. This is one of the reasons why we use safety wire and multiple restraint methods. Retaining all fixtures to the aircraft is most important.

Jon

[birdy]

Hi all, around eight weeks ago a Xenon here in New Zealand had its mast ripped out and tail damaged when the pilot encountered blade flap while backtracking after landing to do another takeoff. Sorry but thats all the details I know.

WTF is go'n on ere????
Whos instructn these people?
Sum instructers need a good eductaion, AFTER theyv had their @ss kicked.
And if its not the instructers, then its these "pilots" that need slapn.
For f$#^k sake, it aint rocket science.
Wouldnt matter wot machine they were in, these people seem to have the unbelievable ability of drown'n ina f%^$n shower.

[bmoore2156]

I have never experienced the high speed blade flap that I am reading about in this thread. The only flap I have EVER had was rrpm less than 100 on a windy day.
Have I just been very lucky? The brand of Rotors make a difference? Or just taking off by the numbers and building the rotors up slow enough?
It sure doesn't sound like you have much time to fix the problem before S!!T hits the fan.
Brad

[Dmorris]

Brad,

Just keep doing it by the numbers and you'll never experience blade flap.

[Passin' Thru]

WTF is go'n on ere????
Whos instructn these people?
Sum instructers need a good eductaion, AFTER theyv had their @ss kicked.
And if its not the instructers, then its these "pilots" that need slapn.
For f$#^k sake, it aint rocket science.
Wouldnt matter wot machine they were in, these people seem to have the unbelievable ability of drown'n ina f%^$n shower.

Birdy, you're a hard man, but by golly you're right! I agree 100%.
The only way you'll ever experience "high-speed blade flap" is if you accelerate forward quicker than your blades can come up to speed.

When your forward speed starts catching up with the retreating blade to the point the retreating blade stalls, The advancing blades zooms up and then dives down the retreating side of the disc, you're in deep doo-doo!

Just from reading some of the take-off techniques discribed in the past couple of years right here on this forum, I shake my head and wonder what in the world I'm missing?? IF what I read is accurate, its a wonder we haven't heard of more roll-over accidents.

Brad ask; Have I just been very lucky?
No Brad, at least not in that respect, it sounds to me like you've learned something about blade management!

[Resasi]

If you do not know what blade flap/ blade sailing is, and have never been aware of how the stick and rotor behave at the onset, you will have a very nasty surprise if, or when it happens.

Depending on circumstance it can come on very quickly and very violently. The stick forces can be extremely high, and rotor blade contact with ground or airframe will generally be costly either to pocket or person, or both.

Not to have instructed the student in it is rather like being instructed in a fixed wing aircraft and never been taught about spins. In primary training I always demonstrated spins, then had my students do them and learn recovery from them. It gave them first hand experience in exactly what to do when they happened, and confidence in their ability to master them.

The need to actually do them was removed from the syllabus in the US and I certainly appreciate the fact that some aircraft are more difficult to recover from spins. Just as some gyros it could be dangerous to actually demonstrate blade flap. One doesn't spin a large transport plane or deliberately flap RAF blades, but, it isn't a bad idea to get into a small training aircraft, or single seat gyro and get some instruction in the phenomena if you can.

Blade flap/ blade sailing can be demonstrated on a windy day when just sitting in a single seat gyro without even taxiing, so it is not hard to get an idea of what it is, how it feels, and what to do to avoid it. It should be part of your training.

[Heron]

Nose goes up, mast starts separating, vibration occurs . . .
Mast tilting back increase AOA and ship jumps in the air . . .
Mast wobbles and goes left tilting the body and hiting the ground . . .
Not pilot´s fault!
What happened to the stick during the event? No mention of hard forces . . .
thanks
Heron

[Steve_UK]

Hi

"Hi all, around eight weeks ago a Xenon here in New Zealand had its mast ripped out and tail damaged when the pilot encountered blade flap while backtracking after landing to do another takeoff. Sorry but thats all the details I know. "


I understand a rotor blade touched the ground during ground handling - the aircraft has since been repaired and is back flying again.

Steve

http://xenongyroblog.blogspot.com/

[bones]

Nose goes up, mast starts separating, vibration occurs . . .
Mast tilting back increase AOA and ship jumps in the air . . .
Mast wobbles and goes left tilting the body and hiting the ground . . .
Heron
Thats one tricky mast to be able to "wobbles" in 2 different directions, and still have the strenght to drag a wide wheel based machine over on its side :blabla:

[JohnR]

I doubt if the shaft driven pre-rotator on the Xenon was ever designed to to meet a 250 rpm pre-rotation figure as quoted. An angled output shaft,universal joints and a splined couplings some considerable distance from the right angle gearbox all combine to restrict the safe transfer of energy at high rotor speeds.

I pre-rotate to a maximum of 180 rpm releasing the solenoid before 50. To achieve this I require an engine rpm around 3000, by this time the brakes are straining its time to go?

[birdy]

Blade flap/ blade sailing can be demonstrated on a windy day when just sitting in a single seat gyro without even taxiing, so it is not hard to get an idea of what it is, how it feels, and what to do to avoid it. It should be part of your training.
Zactly Leigh.
You dont have to risk damage to your machine to show sumone just how destructive it is if left unchecked.
Like Leigh says, just get ol mate to sit in his machine ona windy day, with bout 50 rrpms up, and ease the stick back** so's itll flap, Wen the stick starts to push against his push, get him to EASE it forward.
Then its a very simple explination of wot will happen if he did this at speed, and times the stress level on components by 100s.

**Wen i say let the stick back, i dont mean to the back stop.
wenever im getn sumone go'n and they are likely to flap blades, i make sure they dont let it touch the back stop.
If its just off the stop, then the control systm has sum room to move while waitn for ol mate to chop power and EASE the stick forwad without stressn anuthn.

Remember, the blades have to FLY into a lesser AOA path, you can force um.

Nose goes up, mast starts separating, vibration occurs . . .
Mast tilting back increase AOA and ship jumps in the air . . .
Mast wobbles and goes left tilting the body and hiting the ground . . .
Not pilot´s fault!
How do you figure that to NOT be the pilots fault Heron??
F*** me drunk!!!, if he gets blades flapn that violently, and lets it go till it rips the mast off, who else is there to blame?

Bloodyell Bones, its a good thing you didnt let me have my way with your Exenon, i coulda riped the mast out with all them Gs and killed us both. ;)

[Heron]

Hold your horses both of you! Dam it! :)
Mast tilts back on cracking (not pilots fault)
Ship gets airborne from AOA increase (npf)
If there is still connection to lift the ship, than it is easy to turn it do the torque side (npf)
After the blade hits de ground . . .anada ball game . . . (npf)
Where did you miss the power of the rotor to lift the entire machine, not only flip it to its side?
I did no say it happened . . .it is a theory . . .and may be wrong!
Get it
Heron (listening to Dueling banjos)

[birdy]

Hold your horses both of you! Dam it!
No chance Heron.
Im sick to death of people who dont take responsability for them selves.
It pisses me off that the first thing to be faulted after an incident like this is the manufacturer.
And you wunder why there are buggerall gyro manufacturers?
Im f**ked if id sell you anythn Heron.

I did no say it happened . . .it is a theory . . .and may be wrong!
Well, your theory or not, dont take any responsability off the 'pilot'.
Masts dont just break off.
Frignell, we are all doomed if that was the case.

IF the mast broke, then its very likely it had suffered previous abuse, without inspection, or had excessive time on it.
But to come out first up n say the mast broke [ blameing the maker], and thinkn this takes any responsability off the pilots shoulders is utter crap.

Tyre kickers should stick to kickn tyres.

[bones]

Well i was gonna say something like that but i think you said it better.

[Heron]

Very Aussie . . .
Instead of discuss a theory lets dance with the aborigenes and get all excited.
I was not blaming anyone, you are and by the way 100% sure of your findings . . .give me a break!
No fair dinkum mate!!!
Lets get drunk around the bonfire sometime and get at each others throat, rolling on the floor like two old fags . . . :D
I just want to know if that scenario is possible and can happen . . . ??
thanks
Heron

[Fl90]

rolling on the floor with you, like two old fags. No, no, that scenario is not possible and won't happen.

[Heron]

Ok . . .one old fag then . . . :eek:
Heron

[Graeme Monro]

Very Aussie . . .
Instead of discuss a theory lets dance with the aborigenes and get all excited.
I was not blaming anyone, you are and by the way 100% sure of your findings . . .give me a break!
No fair dinkum mate!!!
Lets get drunk around the bonfire sometime and get at each others throat, rolling on the floor like two old fags . . . :DI just want to know if that scenario is possible and can happen . . . ??
thanks
Heron

Birdy is not that old!

Graeme.

[birdy]

I just want to know if that scenario is possible and can happen . . . ??
Sure Heron, anythns possable, but unlike you, id blame the violent blade flapn leadn to mast failure on the pilot.

Instead of discuss a theory lets dance with the aborigenes and get all excited.
WTF do you smoke Heron?

Lets get drunk around the bonfire sometime and get at each others throat, rolling on the floor like two old fags
Im all for grabn you by the throat Heron, but if you even hinted at taken to the next step, you wont see the next sunrise. THAT, i can garantee, no matter how old i am.

[Heron]

So . . .Am I gonna be your bitch? :D
Again the word blame, where is the blame Birdy?
He could have flapped that thing all the way to the junkyard for all I know . . .
I am 60 . . .not flattering to you have me as a bitch, in special forcebly . . . ;)
Over aged rape? :)
Heron

[maulonir]

Were up post #82, IMHO RotorTom got it on post #2. Rotor Flap.
This thread is now discussing theories for the sake of discussing theories which is fine if you have nothing better to do I guess.

With regard to what the pilot reported, it's difficult to expect an accurate recall of rotor speed, Engine RPM, IAS etc from a pilot thats just been tossed down the runway in a Gyro, so unless there was a black box recorder on board we will never really know how accurate the figures quoted were.
This is especialy true when youv'e just turned big $$$$$$ into scrap and your looking to find a cause that doesn't include you stuffing up.
No one is immune from making mistakes.

[birdy]

Heron, hava natha smoke.

This thread is now discussing theories for the sake of discussing theories which is fine if you have nothing better to do I guess.
Only one putn up theories is Heron, the rest are speculaten, with only fuzzy facts from the pilot to go on.

No one is immune from making mistakes.
Zactly.

[Heron]

What happened! Pre-rotated to my normal 250-270 RPM with the engine at 2500 RPM. I had switched off the solenoid at 90 RPM ( my normal practice.) pushed the Pre-rotator lever forward, pulled the stick all the way back, and applied engine to 4000, checking that the rotor RPM came up again to 270, increased engine power to 4400, nose came up, held nose and increased power, then noted an "unusual" vibration! ( this was not an engine, or rotor vibration, nor a wheel one) I was just considering pulling power, when the craft lifted off the ground, and then "all he'll broke loose!!".

If all was normal for him, why did the ship lifted off?
No mention of stick slap or abnormal movements.
What kind of vibration it was?
Hell breaking loose will be the normal situ, when control is lost . . .
Just did not get the 90 rpm thing with the solenoid . . .?
The presented facts are the fulcrum of our discussion, theories welcome and needed. Pilot further input will help!
Heron (no smoke here for a while)

[EI-GYRO]

I think he just high-speed flapped.

But... is it possible/likely that the prerotator remained engaged, producing the
strange vibration when the stick was pulled back. ?

Viewing a number of videos on Youtube, over the last while, mostly MT-03s,
it seems to me that the takeoff technique is often sloppy, and over-enthusiastic
in the attempt to shorten the takeoff roll.

Usually, you have 4x takeoff length available, so why crowd the blades.??

My 2 cents, value doubtful in the current economic conditions.

[Heron]

El Gyro
That could slow down the rotors to the point of flapping at high speed, he was about to take off . . .good catch!
Heron

[Fl90]

Either way, if you want to entertain the notion that the mast broke before anything else happened, there would still be a big stick reaction....unless the stick was being held firmly on the stop, where there would be no feel for anything in the rotor. That being said, he wouldn't have felt the onset of flap in the stick. So, back to flapping the blades. Ohhh ya, that was said a loooong time ago.

[Heron]

Can´t change parameters . . .
If the mast broke, the stick connection was messed up, no leverage, but he would feel it!
Most likely it broke on ground impact.
Probably the feel was mushy if the mast broke on take off . . .
I saw flapping a couple of times but never had it while at the stick. One time it was so fast the we only heard the thump, blade hiting the top bolt on the + Tail.
So . . .it will be registered as blade flap and loss of control with ground strike on the sequence causing a rollover?
thanks
Heron

[BEN S]

Heron, besides beating a dead horse to death until he dies and then killing him some more, how can you make a statement like this with your experience level in gyros?
Unless you haven't updated your profile...When I had 7.5 hours I couldn't positively control P.I.O much less extrapolate HOW a broken mast would feel on someone else's machine!
Do you always have to play devils advocate or are you just trying to increase your post count? (This was rhetoric....you don't actually need to answer it...)
People might take you a bit more seriously if you didn't make such comments.
Ben S

[Heron]

Sorry Ben, I expressed my opinions . . .
Will refrain from posting.
thanks
Heron

[ckurz7000]

I have talked to several pilots after they had an accident of the non-fatal pilots fault kind. Most rolled over because of blade flapping, one because he did a three point landing at about 50 kts and didn't have the nose wheel straight, another ran out of fuel, etc. None of them -- not a single one -- admitted that it was his fault. When asked right after the accident, they came up with pretty hair raising theories why it happened.

Several of the pilots would eventually come around and understand the mistake they made. In some cases this took a couple of beers and some talking, in others it took months. Some don't want to hear of it to this day.

All I'm saying is that the pilot's perception of how an accident happened is by no means the way it really happened.

-- Chris.

P.S.: And I haven't seen anything like this "high speed blade flapping" that guy Len theorized about in his post on the other board mentioned in the beginning of this thread.

[JAL]

This thread is done to death but purely to fan the ambers of a waning fire I would like to suggsest the following:

I have read on this very forum reports that the Xenon mast is designed to fail on impact to protect the passengers and the integrety of the capsule. Now this to me sounds like a desirable design function.

However is it possible it comes at the price of mast failure if the pilot inadvertably flaps the blades. As this situation exclusively occurs on take off and on the ground that when a pilot flaps the blades lt bends, loosens or even breaks the mast and the gyrocopter ,lurches the direction of the mast and rolls over ( my guess the direction of rotation ). As the mast is designed to shear in the crash, in the subsequent investigation no-one ever can determine what happened first.

This would probably result in very few fatalites as it happens on the ground at lower ground speeds as it is purely the result of the pilot trying to ram to much air through the rotor at too slow of a rotor speed.

If the shear point is designed well then it will never fail under the operating limits of the aircraft but it would be designed to fail outside those limits or it would be just a gimmick.

Blade flap would result in exceeding those limits so technically the mast should fail or its not doing its job.

I really dont know this is just information I have gathered from posts on the Xenon on this forum over the years, whether this is actually the case I am only speculating.

Jordan

[willisbr]

There is a theory that beats most: Even if he can't put his finger directly on what happened...I bet he doesn't do it again.

Now how does that help us? It doesn't. :laser: [thread]

[JetRanger]

I think he just high-speed flapped.

But... is it possible/likely that the prerotator remained engaged, producing the
strange vibration when the stick was pulled back. ?



:first:

I agree 100% with EI-GYRO - pre-rotator may have remained engaged, prevented the rotor from reaching optimal flying speed - result: High-speed blade flap.

:yo:

The machine in question has 'barber-pole' tape on the prerotator shaft for a reason... so you can glance back and see that it has stopped turning once disengaged. Didn't see the pilot mention this anywhere.

Hopefully the investigation will be conclusive and we can put this topic to bed before the image of Birdy and Heron rolling around the campfire sticks in my mind. :eek:
:lol:

[Resasi]

During the 'beating to death of the thread', if any points came up that might be of future assistance in any reader avoiding such a problem, then it can be said that some good has been achieved.:)

[bones]

:first:

I agree 100% with EI-GYRO - pre-rotator may have remained engaged, prevented the rotor from reaching optimal flying speed - result: High-speed blade flap.


Even if and thats a bloody big IF, it was left engaged, dont know how the hell he would have done that, cause you would need 3 hands, but if it was still engaged the bendix has an over run system, so it would just free wheel.

There is no way, and ill put my left nut on this, there is no way, that poxy little shaft will stop a set of 27' blades from spinning up, as long as they were above the 200rrpm.
the book says and i have done heaps of times, 200rrpm will stand FULL power and not flap, i have done it from about 175rrpm, not a hint of flapping.
NOW if he was a habbitual guage watcher, and the tacho was wrong, he nailed it from say 150rrpm, they is a chance he flapped them, however if he was taught to read the rotors he would have known they werent up to speed.
How ever if the front wheel came up the blades were taking the wind, so there is a lot of things not adding up.
But if the front wheel came up and then he put it back on the ground(rotors not loaded) and left it on full noise, then yes he would have flapped them, because they would not be spinning up, but the AS would be going through the roof.
Either way it not the machines fault, a machine will just as easily crash as fly, its up to the person holding the stick to decide what happens, but its all too easy to blame someone/thing else, than to admit they f*cked up

he cant have the cake and eat it too, either one thing or the other, cant have both sorry.

[birdy]

I agree 100% with EI-GYRO - pre-rotator may have remained engaged, prevented the rotor from reaching optimal flying speed - result: High-speed blade flap.
If it was left engauged, [ and driveing] he'd have had the benifit of partial power to the rotor, which equals higher rrpm gain and much less likely chance of flap.
If the pinion was just stuck in mesh, the itd just make abit of noise, not retard rrpm gain.
Either way, im betn we'll never know coz it seems to be pilot error plus pilot shiftn blame, so we aint likely to hear from him again on this subject. :(

[WHY]

Would like a little clarification on "high speed blade flap". As I understand this, the term high speed is referring to the speed of the gyro and not the rotor because if the rotor was at high speed it would not flap. Is this correct ???

Tony

[Passin' Thru]

Tony, you do be korrect!;):peace:

[WHY]

Hi Pete

Thanks for the confirmation, the reason I asked this was, ---the first time I heard the term "high speed stall" as sometimes occurs in racing, it was hard for me to wrap my head around how this occured, but finally got it.

Tony

[EI-GYRO]

Just for clarity, I only meant to suggest that a stuck prerotator might have
caused the strange noise/vibe. I dont believe it slowed the rotor or such.

I think it was a high-speed flap, pure and simple.

It could be argued that the lack of experience in spinning up a rotor without
a prerotator is robbing the current students of the ability to determine whether
they are pushing the rotors too hard.

If students practised hand-starting rotors, even on a static rig, I suspect we
would see less of these takeoff errors.

Perhaps it should be part of the syllabus.

[Passin' Thru]

I think it was a high-speed flap, pure and simple.

It could be argued that the lack of experience in spinning up a rotor without
a prerotator is robbing the current students of the ability to determine whether
they are pushing the rotors too hard.

If students practised hand-starting rotors, even on a static rig, I suspect we
would see less of these takeoff errors.

Perhaps it should be part of the syllabus.

I agree with Fergus on this. Hand starting is not much fun, but one certainly developes an intimate relationship with rotor blade behaviour!:D

[Rotormouse]

It could be argued that the lack of experience in spinning up a rotor without
a prerotator is robbing the current students of the ability to determine whether
they are pushing the rotors too hard.

If students practised hand-starting rotors, even on a static rig, I suspect we
would see less of these takeoff errors.

Perhaps it should be part of the syllabus.

Exactly Fergus!!! :first:

But horrors, no - it's 'old fashioned' to hand start, and the 'new generation' have to have all the whistles and bells to over-complicate matters. Sad thing is, it's their loss, but they don't know what they're missing coz they're not taught what they're missing. All us quaint old fashioned folk need is a piece of string!
All wrong - but as we fly homebuilts we don't actually know anything, do we. :rolleyes:
Please feel free to join me in banging our heads against the brick wall of ignorance. Or maybe that should be arrogance.

[Resasi]

Yes the old 'Armstrong' method for starting both engines and rotors, certainly has served some of us well... and provides a degree of cardiovascular benefit to boot.:)

I must confess to have been a little confused when first told about a sight picture, or rotor blur, when getting up towards the point at which I could begin to fully open the throttle without a rotor tach, but one does pick it up quite quickly.

[Ghetto Wash]

It could be argued that the lack of experience in spinning up a rotor without
a prerotator is robbing the current students of the ability to determine whether
they are pushing the rotors too hard.

If students practised hand-starting rotors, even on a static rig, I suspect we
would see less of these takeoff errors.

Perhaps it should be part of the syllabus.

I don't get it. Keep in mind that everything I know about gyros could be put in one sentance.

Are you saying that if there is rotor flap you would feel it in the resistance when hand starting the rotors?

[birdy]

Are you saying that if there is rotor flap you would feel it in the resistance when hand starting the rotors?
Wen your showed how to hand start rotors, [ with wind] you get a very clear idea of how advancing and retreating blades react at different rates to each other and why theres a teeter hinge. And because of the low rrpm, you can 'see' wots happening.

[MAK]

I agree 100% with EI-GYRO - pre-rotator may have remained engaged, prevented the rotor from reaching optimal flying speed - result: High-speed blade flap.
If it was left engauged, [ and driveing] he'd have had the benifit of partial power to the rotor, which equals higher rrpm gain and much less likely chance of flap.
If the pinion was just stuck in mesh, the itd just make abit of noise, not retard rrpm gain.
Either way, im betn we'll never know coz it seems to be pilot error plus pilot shiftn blame, so we aint likely to hear from him again on this subject. :(

Birdy, you are right you will not hear from that pilot because as far as I know he is not on this forum. He is currently away on a four week holiday anyway so perhaps when he return and reflected on this he might give us some more insight into what happened. I see everybody is blaming the pilot for this accident already, but I just want to remind everyone that this is an experienced pilot (perhaps not as experienced as Mr B... sorry Mr Perfect) but definately not a newbie like myself with only 300hours. Not that I am saying an experienced pilot can not make a mistake, but everyone is talking like they know this pilot and that he doesn't know how to manage his rotor.
Can anybody predict or tell me what will happen if the bendix get stuck in position and perhaps seize and start to run out of sinc with the main ring gear.
We had a problem with our pre-rotator (see separate topic on here) and the bendix and main ring gear started to run out of sinc. This caused huge stick vibration, fortunately still while my wife was busy pre-rotating at about 150 RPM and she could abort. We have the flexible shaft and not fixed one as on this gyro.
I am not a very technical guy (so you guys can correct me if I am wrong) but I don't think a stuck / seized bendix (for what ever reason) and its supporting structures can handle the forces being exerted on it by a 200 or 300RPM rotor, something has to give, I know ours couldn't handle it.
I am not saying it is not pilot error, just cut the guy a bit of slack until the investigation is complete.
For someone then to make a stupid statement / insinuation that because this pilot is not posting, even though he is not on this forum, he is guilty just shows his negative / accusing / stupid mentality.
Anyway, I am zone outbound from this forum, just can stand the negative attitude of some "fellow" gyro pilots.
I can just say that some postings on here is not a good advertisement for newbie gyro pilots or new wannabe gyro pilots. Remember these forums are the first thing wannabe gyro pilots see and I can tell you it doesn't always give an aspiring first impression. If you have anger management issues go and take it out somewhere else, not on this forum, or come visit me and I will resolve it for you.

[Resasi]

Are you saying that if there is rotor flap you would feel it in the resistance when hand starting the rotors?

Rotor flap occurs when there is too much air passing through the rotor disc for the angle of attack that is being asked for by the pilot in his manipulation of the control column. It generally occurs at a rotational speed somewhat in excess of that achieved in the initial stages of a hand propelled start.

The resistance first felt when hand starting rotors is a sum of various forces. Inertia, parasite drag, induced drag to name a few, none of these immediately concerned with rotor flap at this early stage, under normal circumstance. (This however does change when had starting rotors in high winds, and the velocities that occur in the early stages of a greater magnitude)

Blade flap is generally encountered as previously stated, when the amount of back stick/ rearward movement of the control stick is too great for the wind speed of the air passing through the rotor disc. It then creates a situation with the rotor blades where the angle of attack and teetering action of the rotor blades, caused by the lifting blade on the advancing blade side and descending blade on the retreating blade side causes them to collide with the physical stops that limit blade movement.

This collision flexes the blades creating a situation where that blade flex can cause a collision between the outer section of the blade and the ground behind the gyro and/or the tail, with usually catastrophic results, as the forces concerned contain large amounts of kinetic energy

Forgive this rather lengthy and convoluted attempt to explain, I am sure others can put it more simply. Rotor aerodynamics, I find, rather more complex than fixed wing aerodynamics.

[birdy]

Forgive this rather lengthy and convoluted attempt to explain, I am sure others can put it more simply.
Simplicity is my specialty. ;) [ SCG]

For starters,
Rotor flap occurs when there is too much air passing through the rotor disc for the angle of attack that is being asked for by the pilot in his manipulation of the control column.,
is incorrect.
Its the differant AOAs of the advancing and retreatn blades that causes flap, not the AOA of the disc.
You can flap blades with the stick full forward if the wind is strong enuf, coz the reatreatn and advancn blades have greatly differeing ASs. [ AOAs]
Likewise, you can drop into a virtical decent with only 50% flight rrpms and NOT flap the blades, coz the AOA is bout equal all the way round the disc.

And,
It generally occurs at a rotational speed somewhat in excess of that achieved in the initial stages of a hand propelled start.
A rotor will / can flap at 1 rpm.
Any time the rotors teeter they are flapn.
Its only an issue wen they teeter so far as to touch the stops, with force.
This can happen if the machine is left unattended ina strong wind with the rotors untied and with no rpm, [ no matter where the stick is locked] and at flight rrpm, and every rrpm range in between.
But yes, it GENERALY happens wen the pilot feeds too much forward speed into them before the RRPM is up.

[Resasi]

Not only more simply Birdy, but more accurately.

Should have known better to start yapping on a skinful of booze late at night.

I now apologize for demonstrating my lack of judgement, airing my ignorance and thank Birdy for making those points so much clearer.

[grahamegertsch]

But yes, it GENERALY happens wen the pilot feeds too much forward speed into them before the RRPM is up.

Forgive the ignorant question - I'm a newbie trying to understand.

Does the blade 'stiffen' the faster the rrpm? Does the 'stiffness' of the blade then prevent flap?

[L_Butler]

The blades don't change characteristics. What changes is the amount and direction of the forces acting on the blades.

As the rpm increases the centrifugal force increases; this tends to flatten the disc. The upward force from the air is simply overwhelmed by the radial force from the spinning.

Larry

I know centrifugal force isn't real. The directional force concept is the point.

[Heron]

Flap is when the blade "recoils" like a spring, the excess wind bends the blade back and it is release when lift is lost on the retreating side.
The blade will hit the stops and bend the other way, lack of centrifugal force for the wind moment is one cause.
It will feed itself until the blades look like a giant serpent coiling up and down, hiting the ground or the tail if not properly designed.It looks like an S laying down . . .
it is a relation (ratio) between relative wind and rrpm(centrifugal stifness)
Or so I think.
Heron

[Passin' Thru]

Heron, you got it ALL WRONG!
You really need to go back and re-think what you just posted!
Think advancing - retreating blade lift differiential.
You started your last sentence correctly, and then blew it!:der:

[birdy]

Heron, you got it ALL WRONG!
You really need to go back and re-think what you just posted!
Think advancing - retreating blade lift differiential.
You started your last sentence correctly, and then blew it
Thanx Pete, i was wundern how i was go'n to tell Heron, but thankfuly you beet me to it. :)

Does the blade 'stiffen' the faster the rrpm? Does the 'stiffness' of the blade then prevent flap?
Sort of.
As Butler says, its the centruphical force that keeps them [ apparently] ridged.
But this has nuthn to do with flapn.
Yes, if the rrpm is too low for the lift provided [ AOA too high] then they will 'cone' excessivly. [ flexing the hub bar upwards]

Flapping is, the difference in lift between advancing and retreating blades, because of the different relitive airspeeds, wen there is horisontal airflow through the disc.
Flapn happens wenever there is horisontal airflow, wether your taken off, flyn or just prespin'n in wind.
The teetering hinge allows the advancing blade to fly higher n the retreating blade lower, equaly, compensateing for the unequal ASs, so the resultant lift between the two is equal.
Its wen the difference between adv and ret relitive AS becomes too high and the teeter hinge runs out of travel and the limit stops are contacted, wen the blade bar starts to force the stick/head/machine over and high stresses damage components that should be avoided.
This can still happen at high rrpm, with 'stiff' blades, if theres too big a difference in the two relitive ASs.

[bones]

Flap is when the blade "recoils" like a spring, the excess wind bends the blade back and it is release when lift is lost on the retreating side.
The blade will hit the stops and bend the other way, lack of centrifugal force for the wind moment is one cause.
It will feed itself until the blades look like a giant serpent coiling up and down, hiting the ground or the tail if not properly designed.It looks like an S laying down . . .
it is a relation (ratio) between relative wind and rrpm(centrifugal stifness)
Or so I think.
Heron

What f*cking drugs are you on........ seriously if this is what you think about this subject, i will definately not bother reading another bullsh*t comment you write.

[Resasi]

A point. In the UK 'blade sailing' is a term used when the blades are beginning to hit the stops and flex violently. Elsewhere others use the term blade 'flapping' when the flexing of the blade is beginning because it has reached the limits of teeter/flap and the stops are being struck

Perhaps causes a little confusion as the action of an advancing blade rising the the retreating blade descending, which is completely normal, is also 'flapping', or teetering, and how dissymmetry of lift between advancing and retreating blade in forward flight is normally coped with.

Perhaps blade sail is a more precise term.

Does the blade 'stiffen' the faster the rrpm? Does the 'stiffness' of the blade then prevent flap? The blades are able to be relatively light and flexible structures when compared with wings due to the fact that they do stiffen when rotated. But that does not affect blade sail/flap.

[Heron]

There are two movements (one really) with the same terminology, the regular teeter movement is also called flap.
When the movement is on a certain level (envelope) it will be strong and cause stick peculiar behavior, that is what we are talking about the "bad flap" that causes loss of control.
Remove wind (speed) flap goes way, if it was not way over the limit (too late now) blades will never flap if rrpm is in the optimal range no matter what speed the gyro is flying (or taxing), that is when we "firewall" the throttle to speed up on tak off.
When I said, or so I think, it meant I could be wrong and I am sick of people jumping like neandertals off a cave, and this will serve as a point of emphasis for our teachers, they will say: Heron . . .you are partially right my pupil, and so on and so forth.
Those are the forces at work: rrpm, speed for relative wind, blade centrifugal moment and stiffness versus air pressure. That is all folks!
Blade will rise so abruptly that the other one (not producing enough lift) can´t balance the act and let the hub bar hit the stops, causing excessive bending (flexibility), which in its turn will be self feeding if the pilot does not act, throttle back and stick aft. (mistake caught by Stan, the stick is moved forward)
ONe of the reasons DWs can´t be hand started, too much lift on the first stroke and flapping that will make all very awkward.
There! Now I am in the ball park.
Heron
Bones . .behave my friend, I may not be a gyro expert, but I deserve respect.

[StanFoster]

Heron- Not trying to be nick picky, but you said to throttle back and stick aft7m. Its stick forward when I was flying gyros. Maybe the ruules have changed? Ha. Stan

[Heron]

Good catch Stan, thanks!
It is forth with the palanca . . .
Heron

[StanFoster]

Heron- I knew you meant forward. I type stuff backwards once in awhile. Cheers to you and your beautiful country. Stan

[Heron]

When are you coming down? :D
Your mind is better than mine . . .can you remember what came out of that name discussion we had somethime ago about the flap term? I think "mast bump" was mentioned but not adopted . . .
Then Mr. Beaty had a nice explanation with drawings on the flap angle issue.
thanks
Heron

[Rocky]

Apologies for this long delay in posting my SECOND post on this matter, but I have been away from Johannesburg and will not comment further on this issue until I have had some time to actually inspect a few details. This could still be a few weeks as I will be traveling to Australia this coming weekend, but hopefully will get some time this week to get to the hangar.

I deliberately stopped at "Then all hell let loose" because that is exactly what happened....

I am very surprised by the amount of speculation this Forum can generate when no facts are actually available. I have also been surprised by "informed statements" when it has been obvious that the person has no Xenon flying experience.

What I can say is that the lift off to about 1-2 metres from the ground was normal...... then something very strange happened. There certainly was no rotor flap as the numbers were all in the right sectors.

I have no need to blame the manufacturer, as the craft was fully paid for, and I am self insured. If I did do something wrong I will be the first to say so.
Regards
Rocky

[Heron]

Thanks Rocky
We will be all ears when you can talk.
Heron

[Resasi]

Allan, once again glad you escaped with so little hurt, perhaps a tribute to the 'crash cage' and harness the Xenon is, and has. Glad also because you as the pilot involved can provide information as to what may have happened.

With regard to your statement I am very surprised by the amount of speculation this Forum can generate when no facts are actually available...

That there is speculation after any accident, aviation or otherwise should come as no surprise to anyone. It is a human trait. On any Fora that follow particular interests, people will speculate and offer opinions in incidents/accidents such as yours.

In the absence of feedback from participants, surviving or deceased, answers are sought by many to answer, either simple curiosity, the interests of safety for others pursuing/participating in that particular activity, by regulatory authorities, manufacturers, instructors, and or other operators of similar machines.

Many participate in the ensuing discussions, these ranging from idiots to the highly knowledgeable. Idiots muddy the waters and detract from the issue, others can and sometimes do contribute genuinely valuable information or insight on what might have happen.

With your posted experience, all we have to go on, you appear to be beyond a beginner or complete novice, and have flown multiple types of gyro, which can but help. Forgive me but I appear to have missed your first post on this incident?

I was however curious about the statement posted by Eban in the first post on this accident and presumably your words( this was not an engine, or rotor vibration, nor a wheel one)

With over 19,000hrs in flying machines I have experienced vibrations of some sort or another in a number of different aircraft, from gliders through single engine, multi engine, piston, turbine, land and sea. Some are instantly identifiable, most are not.

Highly experienced pilots have tragically misidentified/or not known the reason for a sudden vibration, sometimes with catastrophic results, (Captain in an airline I was with aborted a VC10 for a bad vibration at or near V1 at Addis Abbaba. A/C overan the clearway approx half the pax and crew died. Had he known the cause, a burst nosewheel tyre, given the location elevation and terrain ahead he might possibly have elected to continue with the take off and proceeded to either Nairobi or destination as a safer option.)

That you are not commenting further until more details can be ascertained is quite understandable. That you have posted further on the accident, laudable.

I am sure many would welcome finding out the cause of the accident, it can only help others.

[Heron]

Good post Leigh, I just would remove the idiots comment in there, no need for it.
Heron

[EI-GYRO]

Well, the thread title was ' can anyone share some thoughts with this guy...' so we did. :)

Would be interesting if the wreckage tells us more.

[gyromike]

Good post Leigh. I would not delete the comment about idiots muddying the waters.
:)

[bones]

Rocky,
Sorry i just went back in the thread and couldnt find your other post.
Having just done another 50odd hrs in one of these in the last week or so, it got me thinking about this, and in your psot above it says you were "off" the ground, so that rules out (regular)rotor flap.

Edit i thought it through again and the issue i thought of wouldnt have caused a shake, it was more if the controls got locked?

[birdy]

Im glad youv got the balls to come back Rocky, this can only be a good thing. :)

What I can say is that the lift off to about 1-2 metres from the ground was normal...... then something very strange happened.
This still dont ruel out excessive blade flap.
In the rite [ rong] conditions, you can flap blades to the point of roll over even off the ground.

Im thinkn, the rrpm was too low, but not so low that they couldnt lift the machine.
If your blastn down the road with the disc near flat and at low rrpm, then pull back to lift off, the machine will lift off, but ecsessive teetering will roll it over, and the 'vibration' you felt as more n likely serious coneing caused by the low rrpm.

Its the only explination i can think of for the roll over after lift off and the unusual 'vibration'.

BTW, if you comen to OZ, drop in, youd be more n welcome. :)

[Rocky]

My Original post was on the South African Microlighters Forum and I think it was SARAF who copied som eof it across to this one...(for those that did not see it)
~~~~~~~~~~~~~
I have followed all the comments, and appreciate the input. Hopefully this will generate similar responses. As I have said, I have no problem with any comments, and if I did something wrong I need to understand. I still have lots of questions myself.

Sorry for the delay in the second post on my accident. I have been at the coast and wanted to look at a few things on the craft again.
In the first post I ended with " Then all Hell let loose"....

Basically to recap, Pre-rotated to my normal 250-270 RPM with the engine at 2500 RPM. I had switched off the solenoid at 90 RPM ( my normal practice.) pushed the Pre-rotator lever forward, pulled the stick all the way back, and applied engine to 4000, checking that the rotor RPM came up again to 270, increased engine power to 4400, nose came up, held nose and increased power, then noted an "unusual" vibration! ( this was not an engine, or rotor vibration, nor a wheel one) I was just considering pulling power, when the craft lifted off the ground, and then "all he'll broke loose!!". ....

What happened next was the nose jumped up high enough to be in-line with my line of sight. I immediatedly pushed the sticj forward to hold it down... this is did, (possibly too much!!) and we then somersaulted down the runway.

My normal procedure was to increase power gradually, usingthe runway. On my first solo in this craft, after doing dual with a 115kg instructor, who insisted on pushing Balls to the wall, I lifted off within about 10m, leveling off at about 20metres agl ,calmed down flew straight level down the runway and have never set "balls to the wall" again!!!!

Looking at the location, this started at a point on the runway (08 at Krugersdorp) just where the last hangar to the south of the runway ends. There was a 5-10Kph wind from the South.

So, what has puzzled me, is where did this "uncontrolled input" come from. The vibration that was felt just prior to lift off could have been the pre-rotator been engaged. However, I have inspected it now and there is no sign of any abnormal wear etc. It still rotates easily.

What does concern me is how easily the mast broke, where it broke and how thin the "webs" are in this double "H" section. The mast broke off at the first attachment point to the body. This is some 30mm below the cowling. There is no damage at all to the surrounding glassfibre cowling.

I have given this section of the mast to Braam who will have it inspected by a Fracture Mechanic.

Other than that I don't know what else. Just to say that until that nose rose so rapidly, and so high everthing was normal.

To the guys flying to Gariep, have a great time..I was really lookig forward to it, but I will now be in Australia (earning some money for the replacement craft!!!)
Regards
Alan

[Heron]

Rocky
Other than instruments, what was your perception of the flight to that point? Rotors on usual blurr mode?
You mentioned end of a hangar, was it possible that turbulence formed at some point?
To the pros:
What kind of forces can pull the nose up like that?
Is it possible that the rotor head did not tilt all the way back, for some reason and then got "disengaged" from whatever was holding it?
To me, the history tells: abrupt AOA change . . .
thanks
Heron

[Rocky]

Heron,
As I said, everything was normal, the only exception was that "strange vibration" I had felt. Lift off was normal and everything was going well until ......

Something caused the nose to "jump up" and I imagine my reaction to that was an over correction to keep the nose down.
Alan

[Rocky]

"end of hangars".... I mentioned that because the wind was gusting and the hangars do form quite a barrier to the south of the runway. However, after the incident, it was noted that the wind was changing to about 180- 190.
My initial gyro instructor was very pedantic on rotor management, and my first two lessons were spent totally on "wheel balancing" down the runway. He also insisted on flying "outside the cockpit", which I have been grateful for on a few previous occasions, when instruments have malfunctioned.

Alan

[BEN S]

There are others WAY more qualified to speak on such matters, but from a strictly logic tree point of view, can you definitively rule out that the mast wasn't cracked BEFORE you took off?
What was the flight profile of your LAST flight? how was the landing? Did you pull any extreme maneuvers? Do you keep the machine near salt water/high humidity conditions?
And lastly, can the fracture mechanic tell you if the mast broke then, or earlier?
I once broke my prop bolts and on closer inspection it turned out two of them had already been broken at some point earlier....
Thanks for sharing your troubles with us, it serves to make us all better pilots in the end.
Ben S

[Heron]

By ruling out options we can narrow the search.
Better forcus on that vibration, time of start and kind. I don´t know if its possible for a two blade rotor to get in to ressonance . . . (can it?)
The way you said machine got off the ground gave me the impression it was before due time, maybe I misinterpreted?
Heron

[Rocky]

Ben,
No, I cannot be sure it was not cracked or not.
My previous flight was a superb one, in fact one of my best in this craft. In fact a point I mentioned on my return that particular day.
I have never had a hard landing with EXU, in fact a lovely craft to land. I do not pull extreme maneuvers and I have always had the greatest respect for the machine. I fly in the Highveld, (Johannesburg), here in South Africa.
The fracture mech should be able to determine the mode of failure, and might be able to age but that is a long shot.
Alan

[Rocky]

Heron,
Explain "before due time"? Not quite with you here.

Our initial interpretation of the vibration was the bendix remaining engaged. This has happened on this craft before, on my second ever flight, with the instructor who recognized it. However I check this out yesterday, and couldn't find anything not normal.
Alan

[Rocky]

Heron,
Explain "before due time"? Not quite with you here.

Our initial interpretation of the vibration was the bendix remaining engaged. This has happened on this craft before, on my second ever flight, with the instructor who recognized it. However I check this out yesterday, and couldn't find anything not normal.
I noticed the vibration as I added power at about 40Kts.
Alan

[Heron]

The craft got airborne by pilot input, not some other event. It was a normal take off untill "the hell let loose" . . .
Could the pre-rotator slow the rotor down enough to cause violent flap?
That was my interpretation of high speed flap. Not flapping for low rpm for the given speed . . .we need terms!
thanks
Heron

[EI-GYRO]

If you had a prerotator remain engaged previously, which generated vibration,
it is not unlikely that his recurred, particularly if no damage was evident after
the first occurence, and no parts were changed.

But a hung-up prerotator, particularly one found undamaged, would hardly be likely to cause a machine upset.

I'm not familiar with the Xenon upper mast attachment, but presuming it to be
four bolts joining two facing flanged ends, then the failure of the rear (or front)
bolts could probably cause a radical pitch excursion, and the resulting tumble
complete the separation of the upper mast.

If my guess is way off line, my apologies.

Either way, it seems somewhat less likely to be a simple high-speed flap,
as it should be a ' balls to the wall' takeoff that would be more likely to
generate that.

Fair play to you for coming on here to discuss it.

If there is a question mark over the mast attachment, it would be better found this way, than by a fatal event.

[Rocky]

Heron, El-Gyro,
Guys, thanks for your input. Appreciated.
I have put some images on the South African "microlighters.co.za" forum for those that are interested.
Regards
Alan

[Heron]

Thanks Alan.
WE appreciate your candor.
Heron

[PTKay]

Link to the images:

http://www.microlighters.co.za/viewtopic.php?f=20&t=5037&start=510#p157018

Any comments to the fracture character.
Fatigue or impact overstress?

[Heron]

Thanks PTKay!

[bones]

All i got to say is i feel so much safer, in that cabin now, if thats not proof it works i dont know what is..
But still not sure of what could have caused it, the photos of the broken mast arent real good, will wait for the report.

[Fl90]

unusual vibration

craft lifted off the ground

nose pitched high

full stick forward

somersalted

In your words, this is the chain of events. Also, you considered pulling power, but never said you did. From the photos, it would apear there was considerable speed, especially to somersalt.

If this is incorrect, please correct the misunderstandingsI have.

Phil

[Rocky]

No. I was think about pulling power when i felt the vibration, but as the craft began to fly I didn't.
Yes, what I have tried to describe is the sequence in which things happened.
Alan

[Heron]

Vibration starts on take off run . . .speed and rrpm?
Ship off the ground should eliminate ressonance?
What forces would pick that nose up so sharply?
What was happening with stick?
thanks
Heron

[PTKay]

When you look at the images of the broken mast, you would
agree, that the mast started to brake in the rear part, on the bolt hole.

Before complete failure of the mast it would start to loose it's rigidity,
would become more flexible and could reach some previously
unknown resonance frequency and start to vibrate in an unexpected way.
Eventually the crack would open gradually tilting the mast.

If the mast broke in flight, (I mean IF), the mast would first tilt forward.
The control rods placed rear to the mast and parallel to it, would
keep the rotor plane in it's original position as before failure, but the
rotor thrust vector would move forward, and quite fast it would
be far in front of the CoG, hence creating a strong nose up moment.

This (hypothetical) scenario fits well the description of the chain
of events given by Rocky.


For me it was always an open question how Xenon copes with 2/rev
vibrations using a stiff mast fixed to strong and rigid cabin cage.

There is nothing to absorb those vibrations and fatigue cracks
are almost inevitable on such a point of stress concentration
as the first fixing bolt hole down the mast.

Just my $ 0.02...

[Heron]

Thanks PTKay
The two stronger forces at play, rotor and prop, swinging the cabin . . .
It sounds plausible.
Heron

[Vance]

When you look at the images of the broken mast, you would
agree, that the mast started to brake in the rear part, on the bolt hole.



I wouldn’t agree Paul.

The pictures are not enough for me to imagine the sequence.

I have done enough destructive testing to value a proper analysis and devalue a first impression based on a picture like this one.

I feel it will be useful to have a proper analysis done on the pieces and that seems to be in the works.

I hope that a sequence and time frame can be developed by the experts and an initiating cause developed.

This would be helpful for the other Xenon owners out there who may now feel uneasy about their mast.

This is a low time aircraft without a history of abuse so in my opinion fatigue failure seems unlikely.

I feel the fleet experience would have revealed a design defect like you describe already.

In my opinion the mast on the Xenon is a flight critical part and a failure would be hard to miss.

Unfounded speculation may arouse inappropriate fears.

Thank you, Vance

[Steve_UK]

Hi


The Xenon involved in the incident in South Africa was

ZU-EXU

c/n CAI 030 070T - Engine 914 Turbo

Built September 2007 - ie this is Xenon #030



I know of two other incidents this year ( of course there could be others )

In New Zealand a mast broke whilst taxing in after landing in early 2011 - this was

ZK-XEN

c/n CAK 034 71T - Engine 914 Turbo

Built November 2007 - ie this is Xenon #034


In Chile a fatal Xenon accident happened in March 2011

CC-PTP

c/n CAB 046 72T - Engine modified 914 Turbo

Built February 2008 - ie this is Xenon #046


Please note that there are very few Xenons with the 914 Turbo - perhaps less than 10 examples from the approx 130 Xenons built so far


I am NOT suggesting the three incidents have any common link, I'm just trying to supply some basic raw data.

I hope that the aviation authorities in Chile, New Zealand and South Africa investigate and share their findings among themselves and with the manufacturer too.


Fly Safe

Steve

http://xenongyroblog.blogspot.com/

[Resasi]

Vance your post is the epitome of good, clear, common sense.

Thank you for the additional statistics Steve.

There have been many excellently designed flying machines where some small design flaw has resulted in tragedy. These, when found and corrected going on to long, useful and productive lives.

The facts to date increasingly indicating such a possibility.

[Heron]

Where is the breakaway spot on the Xenon? What kind of system is used?
Heron

[PTKay]

Vance,

thank you for your fair explanation of the phenomenon.
It calmed me down a little before my next Xenon lesson next week.

Regarding the 914 regularity, it is really interesting.
Is it possible, that those engines have some particular
properties, like weight or resonance frequencies different
from the standard 912 or 912 RTS?

If you would analyse this case from pure statistical point of view,
there would be some reason to worry.

But every my professor, when I showed him some statistical results
confirming some significant effect on the trace concerned, asked me,
what would be the biological reason for such effect.

If I couldn't name one, he asked me to change the hypothesis and model,
and calculate again.

Statistics is said to be science... :)

[Resasi]

I may be displaying my ignorance, but is not most research dependent upon statistics?

As for small design flaws, all it took to bring down two De-Haviland Comets with total loss of life of all on board was windows that were designed with crack propagating corners that allowed disastrous explosive decompression at altitude.

[EI-GYRO]

If the New zealand event was not preceded by an obvious exceedance, ( bad flap, blade
ground strike, VERY heavy landing, or similar), it would be very scary.
Even if it was, it's still scary.

Any gossip, Steve, or must we wait we have forgotten about it when the report comes out ?

[Steve_UK]

Hi

Re the NZ incident - I am told that "the rotor blade touched the ground due to bad rotor management during ground handling"

Hopefully the official report will add more in due course.


Steve

[EI-GYRO]

Thanks Steve.

Just read Phil Harwood's book. Curious that wind-assisted rotor acceleration
from low-ish rotor speeds coes under the heading of 'advanced techniques',
rather than 'gyro 101' which is where it belongs.

[Fl90]

I've gotten machines off the ground before the rotor was at full speed. There is a vibration, then there is stick bump. Closing the throttle is the correct response, stick forward while leaving the throttle advanced, is not.

I still think it's flap.

Phil

[Heron]

The best parameter will be how the mast broke, that will give us a time frame to work with.
The kind of flap will be felt at the stick does it not?
Heron

[rick979]

Why are there so many gyro horror stories?

[birdy]

I've gotten machines off the ground before the rotor was at full speed. There is a vibration, then there is stick bump. Closing the throttle is the correct response, stick forward while leaving the throttle advanced, is not.
Ya spoton Phil.

[JAL]

How does the trim work on the Xenon.

If during the take-off run the pilot was holding forward stick in the wheel balance and when he got distracted by the vibration relaxed the forward pressure and if the gyro was out of trim it would result in the nose coming up very quickly, this would also mean that there was probaably a very rapid increase in AoA of the rotor disk, the gyro would have jumped off the ground and the blades may have momentarily ran out of teeter and hit the stops.

The precursor was probably the vibration which diverted the attention of the pilot during the final stages of the take-off run. Still doesnt explain the reason for the vibration or whether the accident and the initial vibration are directly related so you would want to make sure it is not anything to do with the mast.

[Heron]

Why are there so many gyro horror stories?
Rick979:
One for us is too many, it is usually a friend of acquaitance involved!
But . . .there are as many as in other flying crafts, maybe a little more due to a moving wing and the capability of low slow fligth and the alure of it . . .
Nothing to fear but . . .
Heron

[Heron]

JAL
that was my point when I said, got airborne before due time . . .
But he says it was a normal take off untill a couple of meters up and things got catastrophyc . . .
There is another flying surface that can change pitch, the HS coming loose . . . (?)
Heron

[birdy]

The precursor was probably the vibration which diverted the attention of the pilot during the final stages of the take-off run.
Taken off from a sealed strip can be worse than a ruf dirt one.
You cant 'see' the air.
He said it was gusting, and lea ofa line of hangers.
No reason to not suspect a horisontal gust hitn you, and you wont see it comen.
Just coz the soc is steady, dont mean the air 20' away is do'n same.

[Heron]

At least we got this separated in two options: pilot error and structural failure.
PIC error puts a dot on the story, that is it!
Structural failure will be funnier, lots of ifs and what nots.
Heron

[PTKay]

Could this shed new light on this discussion:

http://www.rotaryforum.com/forum/showthread.php?t=29970

[wdr_601]

At least we got this separated in two options: pilot error and structural failure.
PIC error puts a dot on the story, that is it!
Structural failure will be funnier, lots of ifs and what nots.
Heron

Inadequate pre-flight inspection and subsequently not finding the structural flaws (cracks as suspected0 IS pilot error.

[barnstorm2]

Why are there so many gyro horror stories?

Hello Rick!

Welcome to the forum!

I belong to several aircraft and motorcycle discussion groups and we all tend to spend a lot od time analizing problems and accidents.

Since this is a world wide medium, it tends to be a big stage.

Drama tends to get the attention online. My thead covering a non-dramatic flight over flood land a few weeks ago had almost no responses.

Flying experimental aircraft does come with risks but they can get a little out of proportion in the discussions.

Talking about problems is good because it helps all of us avoid them.

.

[Heron]

WDR
Not if the pilot can´t find it!
Taking a machine up and tearing it down is pilot error somehow, we are in a different enviroment.
Not the case in point . . .something strange happened according to the only witness, the pilot . . .can we say he is full of it?
Want to let go on a discussion, fine, but closing it down as PIC error is premature.
Heron

[birdy]

Want to let go on a discussion, fine, but closing it down as PIC error is premature.
Never intended to close it down Heron.
Im just adviseing on wot can happen. The only fault on the pilots part would be ignorance of the possabilities of turbulance.

[Heron]

Never said you did Birdy.
The short form always leave room for interpretation in our Forum.
What I said is: if this is pilot error, not a lot to discuss. He made a mistake that led to the event . . .his state of mind can never be fully understood, unless he recants his movements while at it.
If the cause is elsewhere, than we have to cover all corners and speculate about each one.
My theory about the increased AOA due to mast movement is open and what can happen in a situation like that. I think there is little a pilot can do, if his ship turned rogue on him . . .
thanks
Heron

[viggo hansen]

i have not heard about your problems at take-off with xenon.we have fly about 500 hours with xenon.take-off in all windy condition.i use to prerotate to about 250+-.when ready, release and same time full power.
Re: Xenon Gyro
by FlyingDoc » Wed Mar 30, 2011 3:39 pm

If it wasn't for the integrity of the Xenon cabin, and the four point harness, I don't think I would be writing this!

What happened! Pre-rotated to my normal 250-270 RPM with the engine at 2500 RPM. I had switched off the solenoid at 90 RPM ( my normal practice.) pushed the Pre-rotator lever forward, pulled the stick all the way back, and applied engine to 4000, checking that the rotor RPM came up again to 270, increased engine power to 4400, nose came up, held nose and increased power, then noted an "unusual" vibration! ( this was not an engine, or rotor vibration, nor a wheel one) I was just considering pulling power, when the craft lifted off the ground, and then "all he'll broke loose!!".

The rotor struck the ground on the left, then we ( myself and my trusty Xenon) proceeded to tumble down the runway, we tumbled four times (I suppose 3,5 times) as we came to rest upside down! Still in the harness I was able to push the button, fall to the ground (roof) and proceeded to exit the craft asap!!
I should point out the weather was clear with a 5 - 10 kph crosswind from the south, I was using 08.

As I said, besides a small cut on my left thumb, I am fine, ( other than the fact that my craft is a pile of composite and aluminum)
(tried to attach an image but having hassles with the iPad)
Alan



Posts: 56
Joined: Fri Feb 15, 2008 9:58 am
Location:

[viggo hansen]

i think to little air passing rotor at take-off,speed to low,rotor rpm to low and bladeflapping.

[JohnR]

SARAF

What happened! Pre-rotated to my normal 250-270 RPM with the engine at 2500 RPM.

I wonder if the meter indicating RPM is faulty, would explain why he got blade flap in the first place see below the 250RPM is not possible at those engine rev's.

Motor----------------------------------------2500 rpm
prop/driver pulley at 2.43:1--160Ø P.C.D-1028.8 rpm
Driven V belt,_66Ø P.C.D-------------------2493.8 rpm
allow 3% slip--------------------------------2419 rpm
R/A gear box 1:1----------------------------2419
driver gear at top_10 teeth-----------------2419
driven gear at top 120 teeth----------------210.6 RPM max
If the engine gear is box is 2.27:1 then---222.46 is the maximum

John