Debonding
 

Gulf Has 3 Hel With Debonding Tail Boom All Of Them In The Same Location And Have Been Repaired By Augosta,coz They Under Wranty,and For This One Is Twisted Not Fail Off Like You Said Gayes.the Tail Boom Has Beem Twisted Then Fail Off On The Right Side Of The Helicopter,i Think From My Opnion The Pilot Look The Nose Wheel Insted To Unlook ,whill Checking The Chk List Befor Taxing

.......Yes, and let that be the last time someone posts a reply using text-speak....

KLALA,

I think you should be very careful of your opinions.
I have inspected the concrete exactly where it happened (tail rotor slash marks)very very carefully, I know exactly where he taxied from, he had done about 90 degrees of turning to the left(high tr pitch setting) in a relatively tight turn, maybe 20 foot radius and IF the nose wheel had been locked then there is absolutely no scuff marks at all, and if the nose wheel had been locked I know from experience when I was new on type that he would not have been able to turn that tight. I know you work here and if you had taken the trouble to check, you would have come to the same conclusion.The concrete is quite white here and these marks show up very well.

Are we to assume that if we leave the nosewheel lock in, in a left hand turn the tail "falls off", I hope not, BUT be careful on that left pedal guys, you never know!!!

I know in a left hand turn there could be up to 200HP(thrust and moment arm,you work it out) pushing against a locked nosewheel(full pedal). Much higher stresses than in actual flight I would say. The torn aluminum alloy skin's looked awful thin to my untrained eye, and must admit to a little apprehension now.

I can only assume the Italians have done the maths.

The Captain concerned from my experience of a number of years is a very conscientious and honest guy, I have seen lots of offshore/shuttle shortcuts on checklists done a few myself I am afraid, but the pretaxy/take checks from my observation here are always done, and feel positive that he and his Captain copilot would do the same, unlike the previous incident with this machine on a helideck.

Regards

Mick.

KLALA, from reading your post, and at the same time trying to understand your obvious limited English, am I understanding that you think the pilots were at fault here?
I can tell you that both Captains are very experienced. They had turned 90 degrees to the left from the pad they were on when this happened. If the nose wheel had been locked then they couldn't have done this.

Theoldtimer - strangely enough, just because I fly the Sea King doesn't mean I am ignorant of composite materials - I went on a very interesting university course a few years ago all about composite materials in aerospace structures including visits to industry to see the production and autoclave process in action. I did learn that whilst composite materials are generally lighter and stronger (in compression) than aluminium, any repair process, unless perfectly carried out in ideal conditions, is susceptible to cracking, debonding and delamination and that impact damage to such structures is usually fairly terminal since composites tend to crack and shatter instead of dent and deform like aluminium.

So, since AW are clearly well aware of such issues, one would have thought that the highest level of scrutiny would have been applied to a repair carried out on a vital structure like the tail boom which had suffered a previous tail strike. This clearly did not happen or the tail structure would not have collapsed in the way the pictures show - hence my comment 'WTF' whilst not being constructive is, I think, appropriate since the failure really should not have happened.

Klala,

You better get your torque meter checked. Your on the worng track bubby.:ok::=

Crab - Interesting in your post about the aluminium bending and composites dont. Us Kiwis are very familiar with the way composites let go when they do, and I refer to the mast of the Team New Zealand boat in the Americas Cup on Auckland harbour.

It let go with a hell of a snap like a bomb going off and that was the end of it, whereas in the old days the metal masts would start to signs of failure before they went.

Ned

My first week at Westlands , many decades ago , I witnessed the destructive test of a prototype Scout composite tail boom. One minute it was complete and then after a loud crack there were lots of graphite splinters flying around.
Of course this was the bad old days when all we could get was unidirectional High Modulus Fibre prepreg . The newer woven fibre is a little more forgiving. I suspect the mast was mostly Uni directional .

SASless

AW in Italy sent an e-mail to all operators regarding this incident yesterday afternoon, probably around 24-hours after the incident. They say they will provide updates.

22

Bad news travels fast.......wonder how many emails they got asking questions before they sent out the one they did? I would not want to be on the desk in Vergiate or Gallarate where ever it is these days!

On second thought.....if Ivanna L. was still around.....indeed I would!:E

"Gulf Has 3 Hel With Debonding Tail Boom All Of Them In The Same Location And Have Been Repaired By Augosta,coz They Under Wranty,and For This One Is Twisted Not Fail Off Like You Said Gayes.the Tail Boom Has Beem Twisted Then Fail Off On The Right Side Of The Helicopter,i Think From My Opnion The Pilot Look The Nose Wheel Insted To Unlook ,whill Checking The Chk List Befor Taxing"

BADA-BADA-BOOM!:ugh:

SORRY
 

Mick
I think you are a wise man and I do respect your experience , I did not say both pilots are less of experience but I meant that may be by mistake he locked the nose wheel instead of un locked ,the rezone I said that ,the tail boom will required a lot of force FOR twisted ,this force will come if the helicopter is moving in the taxing and suddenly it stopped in the direction of rotation .but I have news for you from 1 HR I received an e-mail from one of my friends he send me a copy from AD ISSUED BY EASA IN 13 AUGUST 2008 THE AD NO 2008-0157 AND IT SAY THAT SOME OF THE AB/139 HELICOPTERS REPORTED FINDING DEBONDING OF FUSLGE TAIL BOOM PANELS THIS CONDITION IF NOT DETECTED ANDCORRECCTED ,COULD LEAD TO THE STRUCTURAL COLLAPSE OF THE TAIL BOOM ANSTALLATION ,RESULTING IN LOSS OF CONTROL OF THE HELICOPTER ,BY THE WAY AM NOT WORKING IN THIS CO,BUT I HAVE FRINEDS THER ,THANKS FOR THE INFORMATION YOU GIVE ME ABOUT THE CASE

Mmm ....

Well as this drama continues ... it would seem that some of us flying these hotrods have had certain information witheld from us with regard the seriousness of this de-bonding issue ....

I have heard of 'booms going from NEW to delaminated in less than 11 hours time in service ..... This is NOT good .... Agusta had better sort this out sooner rather than later.

Not a happy camper! :mad:

Agusta Statement

I love how they call it an "occurrence", is it still called this if it had let go once the aircraft was airborne :mad:

What was the repair method?
 

How were the disbonds repaired? By injection of fresh adhesive?

The problem with composite materials is that you are flying something that is essentially held together with glue (very hightech glue though) and if the adhesion is anything other than perfect then debonding and delamination can occur.

I was told that another problem is that traditional Non Destructive Testing Techniques don't work on composites so finding voids in the structure or identifying cracks is much more difficult. Any gurus know what techniques are being used nowadays? The Westlands test on the BERP blades on the Lynx was a 'tap-test' and the engineers had to listen to the sound the blade made when tapped with a 2p piece for hollow areas.

I'm sure AW are far more swept up than that now - anyone have the inspection procedures for the tail boom to hand??

Crab, as usual you are absoluty correct. You got in first re your last mail however will still give my input in the hope it will add something useful. I think I may have attended a similar series of lectures on composite structures, construction, stress paths and conditions leading to the degrading of structural integrity. One issue was the detection of de-lamination and the integrity of the bonding agent. As you say put simply metal structures tend to relieve stress loads by flexing, composite remain ridged, hence absorb these loads within the structure. The issue re continuing structural strength with no obvious signs of de-bonding of the skins as in this case it seems, is tricky to detect. Tapping the skins with a coin just doesn’t do the job. I do understand that ultra sound systems can give a better indication of the condition of the honeycomb central core and its bonding to outer skins.
In short, without visible external indications it’s almost impossible to gauge internal structural integrity.
Repair of this type of structure is another matter and extremely complex and generally outside the capacity of the operator. I would be very surprised if the repair indicated in this thread was concerned with the structure, rather more lightly to have been non- structural parts, and with the guidance and approval off A.
That all being said lessons need to be learnt and I am sure they will be.
I remember the discussions on this type of construction years ago when they first arrived and the reluctance of us non believers to believe that they could replace the metal structure

Rough times for mediums
 

So....Aw139s have tailbooms fall off, S76s have substandard windscreens, 332s have gbxs blow up and the S92 has a run dry problem...
Bring back the 412!

Oldtimer - thanks for the input, what you said here is why it seems strange to try and repair such a complex structure as a tail boom rather than replace it. I know the answer will be cost but losing an aircraft (which is what would have happened in this case had it got airborne and then suffered the failure) is so much more expensive.

A very good friend of mine is something of a composites guru but his area of expertise is maritime based as he repairs all the lifeboats for the RNLI. If a lifeboat is crunched he often has to replace much larger sections of the vessel than were obviously damaged, just be sure that any unseen damage is removed as well.