Flt. Lt. Sean Cunningham inquest

[Courtney Mil]

I am sure that we were told about ensuring correct pin placement in the Mk10 decades ago. None of us reported it up the chain as the message was coming to us down the chain. I seem to recall finding a seat pin through the handle only as a trap in the sim one day - not to mention all sorts of sabotage concerning the barostat and the seat top including the scissor shackle area.

[Chugalug2]

None of us reported it up the chain as the message was coming to us down the chain.

Then you were victims of the very syndrome that tuc describes, for it is not supposed to be a one way chain but a closed loop. In other words, every time you discovered an incorrectly placed (and therefore dangerous) pin, it should have become the subject of an SOR (as was). No reports of problems = no problems (except of course for the likes of Flt Lt Cunningham!). In a nutshell you spotlight the destructive effects of the malevolent attack on Air Safety by VSOs. 28% year on year cuts in Safety Assurance expenditure led directly to the gross state of unairworthiness that is present day UK Military Aviation. Elephants? Rooms?

[Background Noise]

I think you misunderstand Courtney's post, and the previous one quoted by DV. I think he is saying that he was aware of it but that he had been made aware if it by the system. He didn't discover it, or fall foul of it. It was taught that way. You don't report that, do you?.

[overstress]

I am sure that we were told about ensuring correct pin placement in the Mk10 decades ago. None of us reported it up the chain as the message was coming to us down the chain. I seem to recall finding a seat pin through the handle only as a trap in the sim one day - not to mention all sorts of sabotage concerning the barostat and the seat top including the scissor shackle area.

Courtney, as I said a few pages ago and I'm glad I'm not the only one. I thought my memory was playing tricks. We were taught that incorrect placement was possible and this was in the 1980s!

Somehow, over the long operating history of the aircraft the knowledge was lost and it is a tragedy that it has cost someone his life. I'm not sure how you go forward from there, but I sincerely hope there are no other lapses in 'corporate knowledge' awaiting others who fly some of the RAF's more venerable machinery

[Chugalug2]

BN:-

You don't report that, do you?.

Not confirming that you are now aware, having been made aware? Well no, and if that is indeed the point of cuefaye's and CM's posts then I apologise. In return might I ask if it was then still the custom to submit an SOR/MOR if such a discovery was made? Is it the procedure to do so now?


Somewhere along the line awareness of a problem at the sharp end (and it doesn't get much sharper than sitting on one of Mr MB's products) should have translated itself into a modification to the Mk10 seat. It didn't, and thus became the contributory cause of Flt Lt Cunningham's death (which was the accident). A classic case of one hole in one slice of cheese lining up with the next (the over tightened shackle bolt, which was the cause of the accident).


With all this awareness, why did this SI not highlight the lack of action to deal with this problem, and why could the shackle bolt have been so inappropriately over tightened after so many years of this seat being in service?


Again, if I now understand CM correctly, if awareness of such irregularities existed, to the extent that Sim checks routinely involved "traps" set into the top as well as in the bottom of the seat, how could this killer bolt have slipped through the system and gone unnoticed by all and sundry? That is why this accident happened and it is brushed off by the MOD as "MB never told us about it". Given past form who can really believe them?

[cuefaye]

DV,


Subsequent posters have covered your questions I think.


That the design fault and its potential consequence (now, tragically, real) was widely known of and tolerated all these many years is both unbelievable and outrageous; and in this context I fully agree with the concerns that Chug and Tuc rightly hold. I know of one of the early and most respected Hawk development test pilots who did all he could to resolve the issue over many years, and which I'm told gave him much worry into his retirement. That in itself beggars belief that the system is so lacking.


I believe the SI fulfilled its remit, its recommendations are very clear, and in no way did it fail in its purpose. Now it is incumbent on others up the gravy train to very belatedly act: which is, I think, where CM and myself came from (with apologies if I'm incorrect Courtney).

[dervish]

This is all boggling my mind. Well done you old pilots for being honest enough to say you knew of this in your prime. I think you should write to your MPs and say you believe the Coroner was misled by incorrect assumptions in the SI report.

On the subject of reporting, am I correct in saying the Odiham test pilot was hauled over the coals and accused of lying about reporting a major safety problem on Chinook? Then only recently discovered to be telling the truth all along? If I was a pilot I might think twice if I knew I'd be dragged through the mud publicly by some lying bastard of a VSO.

[overstress]

That the design fault and its potential consequence (now, tragically, real) was widely known of and tolerated all these many years is both unbelievable and outrageous;

Tolerated? What were student aircrew to do other than understand the potential trap and make a mental note not to fall into it? More of a 'don't do it this way', known about and taught. I can't explain why it seems to be news to the SI though.

edit: looking back I realise that you may be talking about the scissor shackle and not the pin

[tucumseh]

I can't explain why it seems to be news to the SI though

On the two occasions I've had to submit evidence to a BoI I was initially gratified they had asked the correct person (as I held airworthiness delegation on the subject kit).

On the first occasion my evidence was omitted entirely because the RN did not fancy embarrassing a senior RAF officer well known to this forum. In short, the evidence was a subset of what I submitted to Haddon-Cave 20 years later, which he characterised as "savings at the expense of safety". No one died in that one.


On the other occasion (multiple fatalities) my evidence was essentially the same, although specific to that aircraft type. This time, regulations implemented properly, but then over-ruled by a non-engineer behind our backs. Again, the BoI report was rendered complete nonsense by the omission, and today MoD deny the investigation took place or my report ever existed. A copy was submitted to the Defence Committee last month.....

I fully accept Courtney's assertion the SI did a good job, given the constraints they were under. I'd just love to see their unedited report. I always suspected what happens, but during the MoK Review it was a real eye-opener seeing the sheer scale of changes made to the CHART report. It isn't often you get to see the original. What they eventually released still said the aircraft wasn't airworthy, so imagine what the original said! ZA721 (FI 1987) was the same. The AAIB were apoplectic over what was omitted. What would stop such interference?

[cuefaye]

Tolerated by the authorities: the pilots had no choice.

[vulcan558xh]

bastard of a VSO.
--------------------------------------------------------------------------------------
Please excuse my ignorance, but could someone tell me what is a VSO. I am up to speed with the rest.
Thanks.

[lj101]

Very Senior Officer

[dctyke]

With all this awareness, why did this SI not highlight the lack of action to deal with this problem, and why could the shackle bolt have been so inappropriately over tightened after so many years of this seat being in service?

It could NOT be overtightened when fitted in the seat bay because it (the drogue shackle) was pre-assembled (bolt already fitted) before sliding into an open scissor shackle and the BTRU cocked. If it was too tight it would simply of not have gone into the scissor shackle. It was the advent of extending seat servicing times in recent years which meant they had to frig a way of undoing the drogue shackle bolt to enable the beam crack testing to be carried out. Simply the shackle system was never really designed to have the bolt removed/fitted in-situ.

[Courtney Mil]

I'm sure someone here has checked already, but just to confirm that there is no mention of either the bolt (as expected) nor the possibility of incorrect fitment of the seat pan firing handle pip-pin in the aircrew manual. Albeit that I do not have access to an up-to-date copy.

[JFZ90]

I'm a bit confused as to how the "incorrect pin placement" was known, as if I understand the SI correctly, the handle had to be in position 2/3 which was far from normal - essentially cause for panic - as it could be accidentally set off with only 6Kg force in this volatile position.

Was this delicate position 2/3 issue really known and understood?

Was the risk of threading the strap through the handle and initiating the SPH known? (It seems it was) If so what was the mitigation? Strap in with pin in the SPH? In this case the risk should never have arisen as the SPH should always be in position 1, and with a pin in (which can only be inserted correctly if in position 1), it is not possible for the strap through SPH risk to move it to Position 2/3.

Do you see what I mean? What am I missing?

[Chugalug2]

dctyke:-

It could NOT be overtightened when fitted in the seat bay because it (the drogue shackle) was pre-assembled (bolt already fitted) before sliding into an open scissor shackle and the BTRU cocked. If it was too tight it would simply of not have gone into the scissor shackle. It was the advent of extending seat servicing times in recent years which meant they had to frig a way of undoing the drogue shackle bolt to enable the beam crack testing to be carried out. Simply the shackle system was never really designed to have the bolt removed/fitted in-situ.

Thanks for that, dctyke. I know that this is the second time that you have posted to the same effect and you may well have to do so again (given that you are dealing here with aircrew!) So the big change regarding this bolt is that it was never undone in situ, but suddenly all that changes and it has to be. Ergo, it has to be replaced and done up again, ergo stuff happens...
Why was this not in the SI, I wonder...

[Easy Street]

JFZ90,

You are right to say that the a mis-routed strap could not move the handle while the seat pin was in. The sequence would be strap in - seat pin out - taxy - tighten straps. That's because it's usually possible to tighten the straps a little more once you've been sat down for a bit. Common times to do this might be pre-take off and before aerobatics (the S in HASELL checks = security). If your business is aeros, you'll want tight straps!

Alternatively, you might move your leg a lot after making the seat live (eg a full rudder check) and in doing so apply enough tension to the strap to move the handle.

[Easy Street]

dctyke,

The SI said that the shackle was loose enough that it would have had free movement when unloaded, so I figure the scissor could have been engaged through it? They concluded that it only became locked under the loading of the deployed drogue.

Still, it's another example of the pitfalls of the over-engineering beloved of some who lack the balls to sign underneath "do nothing". Disturbing systems that are meant to be left alone usually has some undesirable hidden consequence. At least, that was the approach I took on aircrew turnarounds ;-)

[Distant Voice]

It could NOT be overtightened when fitted in the seat bay because it (the drogue shackle) was pre-assembled (bolt already fitted) before sliding into an open scissor shackle and the BTRU cocked

So who provided the drogue shackle? The chute bay?

DV

[Flight_Idle]

Easy Street,


I'm a bit puzzled about how a shackle would lock under the load of a drogue shute at zero zero, yet get freed at 50+ knots airspeed.


I suppose there's lots of scientific detail in the tests which are not published, because the general viewer would not be expected to understand it, but it leaves many wondering about it.


Most technicians would wonder why a shackle needs to be compressed by a bolt anyway, rather than have the whole mechanism finely machined, with correct gap etc.


An engineering puzzle which I wish I had more information on & would be most intrigued to have the opportunity to have a 'Fingers on look' at it all.


I just cannot believe that there were not specifically stated gap tolerances.