Guimbal Cabri G2 crash Lelystad Airport

[Rotordent]

This morning on EHLE a Guimbal Cabri G2 has crashed . 2 pob. no casualities.
First reports suggest mast bumping.
According reports it must be the PH-WTWGuimbal Cabri G2 serial 1003ex F-WWHG, F-GXRU

[Flying Dutchy]

That is bad news, I have seen it flying several times. Mast bumping however does not sound really logical to me as the G2 has a 3 blade fully articulated head....

[ReverseFlight]

Rotordent, sounds like you are not a helicopter pilot. Where did you get your "first reports" from anyway ? Another non-pilot or journalist ?

Lesson 1 for you:
Mast bumping does not apply to fully-articulated main rotor systems.

[9Aplus]

Soft landing = Crash!?

Crash with Soft landing !?

or no crash at all...

I am confused :*

[stringfellow]

come on then what happened???????????

[Heliboy68]

From one of the Dutch News websites, it would appear that the accident, which occured on 31/7/2011, was a training flight. As a result of a heavy landing there was a tail strike.

Nieuws.nl - Helikopter zwaar beschadigd bij oefenvlucht (http://binnenland.nieuws.nl/653494/helikopter_zwaar_beschadigd_bij_oefenvlucht)

[Heliboy68]

Helicopter was on training flight and had heavy landing. Only details are 2 POB and tail strike. Too much aft cyclic maybe:uhoh:

[helihub]

The following is a statement from Bruno Guimbal who told me I can post this. He broke away from a holiday to participate in the complete investigation the day after the accident at Lelystad. I'm literally just cut/pasting the following from the email he sent me.
___________________________________________________________

I will not interfere with the official services report nor with our own manufacturer report, but this is a first set of facts :

- The two pilots (instructor + pilot starting his TR) were flying a full auto to the grass and they were satisfied until they decided to go around on short final to avoid a crossing taxiway in front of them,
- For some reasons, the power recovery did not occur. The engine was running after landing, and was run again and found in good condition, as the entire powerplant and main transmission, during investigation.
- The helicopter once bounced on the grass after the taxiway, then the pilot achieved a very smooth, level landing.
- At a very low RPM, the blades contacted the tail boom and one stroke it down to the internal shaft,
- The helicopter suffered no damage in its main, forward part, including landing gear and engine installation,
- One blade was found undamaged, another one with very minor repairable damage at its tip. The last one is damaged beyond repair but only on its trailing edge. The rotor was flying and controlled during final landing.
- The rotor head and transmission is undamaged since the tail transmission was unplugged through its splines.
- The helicopter was released to its owner the same day by the authorities. It is expected to be repaired soon at a (hopefully small) fraction of its cost.

We have two early comments :
- Because "mast bumping" was cited on the internet, we recall that this is meaningless with a semi-rigid rotor like the Cabri's one,
- During the Cabri certification testing with the authorities, extensive in-flight evaluation, with instrumentation, was conducted of rotor-to-tail boom clearance and were concluded as very satisfactory. Manoeuvres performed included hard landings at rotor speeds as low as 60% of nominal, and aerobatics well beyond the allowed flight envelope.

Helicopteres Guimbal will issue a set of recommendations in accordance with the airworthiness authorities.

I allow you to release the above with my name, but only in its entirety.

[tecpilot]

On the 17 may 2011 a Cabri in Germany got an full engine failure on comparable conditions during an exercise autorotation. The pilot was able to land without further damage.

According to the german accident board they tested while investigation 3 different carburetors and on each trial the engine failed during low g conditions.

Guimbal assured an isolated problem on the affected german helicopter s/n 1016. :confused: without further impact on the other ships.

Seems to me not a question of recommandations Mr. Guimbal!

[Arrrj]

Well done Mr Guimbal :ok:

How refreshing to see the boss of a helicopter company straight onto the project. I am sure that we would all like to see his counterparts do the same thing - doubtful though.

There are many of us looking to buy new machines that would love to know what happened to that R66 that crashed in South America...

Cheers
Arrrj

[9Aplus]

@HillerBee (http://www.pprune.org/members/124863-hillerbee) now...
we like to hear your statement (story).

(If possible - because of official procedure)

[eivissa]

@Tecpilot:

That engine failure didnt occur during a practice autorotation but during a low g pushover! The pilot entered autorotation because of the engine failure and was able to restart during AR.

Well done by the pilot and Ive seen the videos! They replicated it several times over the airfield after having changed parts on the engine. The engine quit everytime they made a low G pushover!

In fact there was another incident with the G2 in Germany. This is first hand, because the instructor is a friend of mine.

They were on a training flight in the same region of the above engine failure a couple of days later, but different machine. During throttle chop to enter a practice autorotation, the engine quit. Just like in the other incident, they were able to restart during autorotation and got home safely.

[FLY 7]

It always surprised me that, for a new helicopter, with what appeared to be a forward thinking approach, it doesn't have fuel injection.

[S76Heavy]

Haven't flown recips for a very long time, but could it have been carburettor icing? I hear it's been quite humid over there for a while, and it was certainly something that was drilled into me during my initial training.

Looking at the Armada OH6 which lost its tail as well, not a good week for autorotations..

[eivissa]

The G2 is equipped with an "automatic carburetor heater" as standard.

[chalmondleigh]

This is not a new phenomenum for carburettor equipped piston engines. I believe that early models of the Spitfire had a similar problem in dog fights with the Me109. German pilots were able to evade the Spitfire by pushing over into a steep dive; the Me109 had a fuel injection system not the float chamber equipped carburettor of the Spitfire.

[Peter-RB]

Refreshing it certainly is, a man who is prepared to explain what happened when the brown was happening.

I only hope this good and honest situation is read and absorbed by Frank R, ...I cannot actually remember anything so straight from that side of the US, well there was one G Washington, but he was from the east side!!.

Perhaps the New World, will learn from the example of the Old, I'll start counting, slowly !

PeterR-B

[Peter-RB]

The Spit pilots learned very quickly to go inverted when trying to dive onto the Hun 109s, and eventually a lady engineer worked out a type of washer with a special hole in it fitted into the floatchamber cured the neg g on the big carbs!
After that the Hun became very cautious for when in a dive the Spit could easily outdive the 109 which started to pull its wings off when trying to pull out from such high speed dives, the Spit however had no such trouble.

Peter R-B

[tecpilot]

Not so much delivered ships with not so much flighthours but several engine problems and some accidents are a really bad ratio.

[Senior Pilot]

The Spit pilots learned very quickly to go inverted when trying to dive onto the Hun 109s, and eventually a lady engineer worked out a type of washer with a special hole in it fitted into the floatchamber cured the neg g on the big carbs!


Mrs Shilling's orifice (http://www.pprune.org/aviation-history-nostalgia/453841-battle-britain-film-opening-sequence.html) was the cure referred to. Fascinating lady, (http://upload.wikimedia.org/wikipedia/en/d/de/Beatrice_Shilling.jpg) given the attitudes of the day :cool:

[Rotordent]

After posting the first message about the crash of the Cabri at Lelystad, it is interesting to see the reactions. In my opinion this community is to inform about the helicopter world, to learn from mistakes and not to burn down other people. Respect!!
Altough there are some posts removed ( from the pilot involved) it is good to read the answer from the designer of the Cabri . This is the power of this community and I am glad to be part of it.

rotordent.

p.s mastbumping was a bad transalation from me for tailboom strike

[RVDT]

Any float type carburetor relies on gravity for the float to work.

If the float stays at the top of the chamber it will not replace the fuel used in the carburetor as the needle valve is shut.

Try it in a frame with the same engine that is allowed to operate at zero G i.e plank C172 for example.

It happens very quickly and a plank will restart due to windmilling (if you don't get too slow) a helicopter will not unless you restart it!

Maybe the rotor on the G2 is too good for the engine!

[topendtorque]

seems to me the information thus presented is confusing in the extreme.
"for some reason the engine did not respond"
"and who is prepared to explain"
"they decided to go around"

some people here talk of zero G causing a short term engine power loss?

did the zero G occur, if so where? from an auto commenced at fifty feet? or at commencement of the auto at some time above where the (what I would call a long term) decision to go around when a taxiway loomed up in the sights?

I.E. a momentary loss of power might have occurred as suggested but well before the decision to go around as presumanly the PIC knew at that time that the engine was running OK and therefore elected to apply power.

Therefore the auto commenced at a high height, high enough for even a slightly prolonged brrp brrp to have sorted out into a smooth running idle.

From my point of view the suggested certification flight test regimes would have included sudden throttle roll offs or more correctly, abrupt downward selection of the collective within the profile of maintaining allowable maximum RRPM and ERPM.
Those tests would have sorted out whether there was ever a momentary loss of power capable of being experienced in the engine. Is there such mention in the AFM? No? well it doesn't happen then!

I believe that unless you are flying a helicopter with negative pitch capacity that negative G will not occur in any auto unless one wound the throttle off during a low g pushover or perhaps a violent pushover. Who in their right mind would do that?

I do not think the engine suffered negative G. At all times during positive to flat pitch maneuvres the aircraft are usually assuming a not less than one G profile.

Therefore we have not had yet - an explanation.

It is said that the machine is fitted with an automatic carburttor heater.

It is not said whether the device was tested as functioning correctly.

In my view either;

the engine suffered a carby ice blockage which can be undectable until power on is selected.

However "the pilot acheived a very smooth level landing", means to me that if the engine quit suddenly at the go round decision height that the airraft was not then in a profile which meant a heavy landing would ensue.

or ;

the collective was selected downwards during the run on quickly enough for the M/R to touch the tail whilst the cyclic was selected rearwards to arrest forward run on speed.

I have done such myself in a '47, threw the collective down to arrest forward movement as a final resort to save the aircraft going over a very nasty drop in front. I was in a freewheel failure auto at the time with no choices about selecting a longer run on area.

The second scenario leaves conjecture about any problem of the helicopter or engine in the dustbin.

Rearwards cyclic can be selected to arrest forward speed, during practice autos but the collective must be right up or being lifted upwards at the same time.

In no strectch of the imagination could one suggest that the A/C 'crashed' during such an incident.
regards tet

[Flying Dutchy]

I don't think it is all that complicated; EHLE has a 1250m long runway with on 1 side taxiways at equal distance which creates 4 grass segments. autorotation starts on final at 700 ft and normally ends somewhere on segment 3. It is normally a full auto with recovery into a running landing. They either ended at the end of segment 2 or at the end of segment 3 and tried to recover to go over the taxi way and land on the next segment. usage of the collective during the second flare, which normally starts around 100-120 ft is not necessary, at least I never used it in a flare and I did at least 100 auto's on a 3 bladed bird (H269). After the second flare we level ship at around 20ft or so and use collective only to cushion landing... It looks like the recovery did not work out with hard ground contact as a result, they pulled collective to pass the taxi way and then landed soft in the next segment. Question remains when did the blades hit the tail boom; after the first hard landing or during the second while giving aft cyclic to reduce speed while rotor rpm was already way too low....

[eivissa]

@ torpendtorque:

dont get the accidents/incidents mixed up. The low-g i referred to, happened during one of these tryout flight were a passenger gets to touch the controls from the left seat. After the passenger applied too much aft cyclic, the instructor responded with forward cyclic to stop the climb. This low-g situation is the moment, the engine quit.
After entering autorotation, the instructor succesfully restarted the engine and flew back to base safely.

The other incident didnt involve low-g, but a sudden throttle chop in order to iniciate a practice autorotation. Again, the engine quit, though different machine.

All the above happened in Germany. Finally there is the accident this thread is actually about. In this case, no one mentioned low-g in the first place.

[krypton_john]

Anyone know why a thoroughly modern machine such as this has a 19th century technology fuel delivery system with the associated failure modes still present?

[Vertical Freedom]

should be fuel injected, then also no ice probs :}