Flt. Lt. Sean Cunningham inquest
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Correct bolt and correct depth nut?
I am reading this with interest as I am currently stripping and rebuilding a couple of MB mk 9 seats from a Harrier for a museum.
I have, tonight just installed the shackle bolt which does have a shoulder. This means you cannot over tighten if common sense were applied. If I were to use another bolt with a shorter shoulder it could easily be clamped, rather than a loose fit. If however a nut that perhaps had a counterbore on its inside or indeed was over tightened, I would say that would also cause an issue. It is interesting to note the comment that the correct bolt has a short head. This is true for the Mk9 seat and you simply use a cranked ring spanner. If you lift the scissor shackle up it really is not an issue to fit a spanner.
Regarding torque settings, I will check the manuals that I have and report back.
I have, tonight just installed the shackle bolt which does have a shoulder. This means you cannot over tighten if common sense were applied. If I were to use another bolt with a shorter shoulder it could easily be clamped, rather than a loose fit. If however a nut that perhaps had a counterbore on its inside or indeed was over tightened, I would say that would also cause an issue. It is interesting to note the comment that the correct bolt has a short head. This is true for the Mk9 seat and you simply use a cranked ring spanner. If you lift the scissor shackle up it really is not an issue to fit a spanner.
Regarding torque settings, I will check the manuals that I have and report back.
It's been a while since I flew in a seat with the Hawk-style scissor shackle, and would appreciate a reminder from someone with more recent experience. I have vague recollections of wiggling the drogue shackle during the seat checks, expecting to find a little movement. Would this have been aimed at discovering the fault that appears to have killed Sean? In recent years I've heard people discouraging the practice of touching seat components during the checks, but to my mind the shackle and the top latch (incorrectly engaged in Wolfy Harland's accident) were two parts that could best be checked by feel. What is the current advice and practice?
Thread Starter
From the Lincolnshire Echo
The inquest into the death of Red Arrows pilot Sean Cunningham heard that life critical safety warnings about ejection seat maintenance were first issued to foreign air forces more than 20 years ago, but not the Ministry of Defence.
Seat manufacturer Martin-Baker Aircraft Co. Ltd advised the Pakistan Air Force in 1990 not to over-tighten a key nut and bolt in the seat mechanism.
Over-tightening can cause pinch and lead to the parachute failing.
The instruction was to ensure some free play in components and have one to one-and-a-half threads showing through the nut.
Similar advice to other air forces including India, Italy and Finland followed.
Richard Seabrook counsel for the Coroner, put questions to Michael Cameron, Martin-Baker’s senior after sales executive, who was the company’s chief technical instructor from 1999 to 2008.
Mr Seabrook asked him: “You cannot explain why advice particularly relevant to the MoD was not communicated to the MoD at or about the same time [as foreign air forces]?”
Mr Cameron replied: “I cannot explain this but it was nine years before I got there.”
Mr Cameron said that until Flt Lt Cunningham’s death he was unaware of the risk of the mechanism pinching if over-tightened.
Bernard Thorogood, for the Health and Safety Executive, said the concern about over-tightening was a “risk to life” issue.
Mr Thorogood asked Mr Cameron: “There was concern in 1990 about the thorny issue at the heart of this inquest.
“This should have been passed onto customers?”
Mr Cameron replied: “Yes.”
Mr Thorogood then put to him: “This should have been dealt with in a way that left customers in no doubt?”
Mr Cameron replied: “Yes, but I was not there at the time.”
The court heard that after the accident it was discovered the key bolt in the mechanism in Flt Lt Cunningham’s ejection seat appeared to have bent in operation.
Asked what conclusion he drew from this, retired Martin-Baker engineer Neil Mackie, who worked in its quality assurance department, replied: “Vastly over-tightened.”
Flt Lt Cunningham died after his ejection seat fired from his aircraft while it was on the ground at RAF Scampton on November 8, 2011. His main parachute failed.
The inquest continues.
Read more: Sean Cunningham inquest: foreign air forces were given ejection seat safety warnings more than 20 years ago, but not the RAF | Lincolnshire Echo
Seat manufacturer Martin-Baker Aircraft Co. Ltd advised the Pakistan Air Force in 1990 not to over-tighten a key nut and bolt in the seat mechanism.
Over-tightening can cause pinch and lead to the parachute failing.
The instruction was to ensure some free play in components and have one to one-and-a-half threads showing through the nut.
Similar advice to other air forces including India, Italy and Finland followed.
Richard Seabrook counsel for the Coroner, put questions to Michael Cameron, Martin-Baker’s senior after sales executive, who was the company’s chief technical instructor from 1999 to 2008.
Mr Seabrook asked him: “You cannot explain why advice particularly relevant to the MoD was not communicated to the MoD at or about the same time [as foreign air forces]?”
Mr Cameron replied: “I cannot explain this but it was nine years before I got there.”
Mr Cameron said that until Flt Lt Cunningham’s death he was unaware of the risk of the mechanism pinching if over-tightened.
Bernard Thorogood, for the Health and Safety Executive, said the concern about over-tightening was a “risk to life” issue.
Mr Thorogood asked Mr Cameron: “There was concern in 1990 about the thorny issue at the heart of this inquest.
“This should have been passed onto customers?”
Mr Cameron replied: “Yes.”
Mr Thorogood then put to him: “This should have been dealt with in a way that left customers in no doubt?”
Mr Cameron replied: “Yes, but I was not there at the time.”
The court heard that after the accident it was discovered the key bolt in the mechanism in Flt Lt Cunningham’s ejection seat appeared to have bent in operation.
Asked what conclusion he drew from this, retired Martin-Baker engineer Neil Mackie, who worked in its quality assurance department, replied: “Vastly over-tightened.”
Flt Lt Cunningham died after his ejection seat fired from his aircraft while it was on the ground at RAF Scampton on November 8, 2011. His main parachute failed.
The inquest continues.
Read more: Sean Cunningham inquest: foreign air forces were given ejection seat safety warnings more than 20 years ago, but not the RAF | Lincolnshire Echo
The inquest heard of the ongoing work to improve ejection seat safety.
Martin Lowe, the Ministry of Defence head of engineering, for aircraft escape systems and a former RAF chief technician, said that there is a proposal from ejection seat manufacturer Martin-Baker, at his request, involving a re-designed drogue shackle nut and bolt within the seat mechanism.
Mr Lowe said this is effectively a shoulder bolt, beyond which the nut cannot go.
This would make over-tightening impossible and therefore avoid the risk of the parachute not come out.
It is anticipated that the new nut and bolt and a special tool will be introduced by May or June of this year.
Mr Lowe also said a small metal plate is being developed to help prevent pilots inadvertently activating the ejection seat firing handle.
He said the plate has five benefits.
It prevents the safety pin being inserted while the seat firing handle is in the unsafe position and there is a groove to help guide pilots with insertion.
The plate also stops the handle being pushed forward to complete the ejection.
Inadvertent insertion of the safety pin between the handle and the housing is averted and harness straps should not snag on the handle.
This measure is due to be in place by the end of this year and will apply to Hawk T1, T2 and Tornado jets and the Tucano trainer.
Read more: Sean Cunningham inquest hears of ongoing work to improve ejection seat safety | Lincolnshire Echo
Martin Lowe, the Ministry of Defence head of engineering, for aircraft escape systems and a former RAF chief technician, said that there is a proposal from ejection seat manufacturer Martin-Baker, at his request, involving a re-designed drogue shackle nut and bolt within the seat mechanism.
Mr Lowe said this is effectively a shoulder bolt, beyond which the nut cannot go.
This would make over-tightening impossible and therefore avoid the risk of the parachute not come out.
It is anticipated that the new nut and bolt and a special tool will be introduced by May or June of this year.
Mr Lowe also said a small metal plate is being developed to help prevent pilots inadvertently activating the ejection seat firing handle.
He said the plate has five benefits.
It prevents the safety pin being inserted while the seat firing handle is in the unsafe position and there is a groove to help guide pilots with insertion.
The plate also stops the handle being pushed forward to complete the ejection.
Inadvertent insertion of the safety pin between the handle and the housing is averted and harness straps should not snag on the handle.
This measure is due to be in place by the end of this year and will apply to Hawk T1, T2 and Tornado jets and the Tucano trainer.
Read more: Sean Cunningham inquest hears of ongoing work to improve ejection seat safety | Lincolnshire Echo
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Given that the RAF/MOD have in the very recent past been down a very similar road it's becoming pretty obvious where this is headed and what's coming next, albeit perhaps on a smaller scale (but given the PR context -maybe not).
Following on from Nige321's above, there's actually quite a lot in the Lincs Echo:
Lincolnshire Echo | Search on Lincolnshire Echo
Sadly, they've stopped the live-ish tweets, but they seem to be covering the inquest most days.
BBC Look North (Yorks&Lincs) say they plan to have a reporter there every day - so far Caroline Bilton's reports have been pretty good. You can find that version of Look North on Chan 957 on Sky, not sure about other providers.
Although the MAA will not publish their SI until the last day of the inquest, Cdr Danny Stembridge, of the MAA, is due to give evidence on Thu 23rd.
The last planned day for witnesses is Tue 28 Jan, then the Coroner takes a day or two to write up his findings.
airsound
Lincolnshire Echo | Search on Lincolnshire Echo
Sadly, they've stopped the live-ish tweets, but they seem to be covering the inquest most days.
BBC Look North (Yorks&Lincs) say they plan to have a reporter there every day - so far Caroline Bilton's reports have been pretty good. You can find that version of Look North on Chan 957 on Sky, not sure about other providers.
Although the MAA will not publish their SI until the last day of the inquest, Cdr Danny Stembridge, of the MAA, is due to give evidence on Thu 23rd.
The last planned day for witnesses is Tue 28 Jan, then the Coroner takes a day or two to write up his findings.
airsound
So how, or why was I (and many others) instructed to leave only 1 1/2 threads showing through the stiffnut and check for movement in the scissor-shackle from 1988 until 2000?
Must have imagined it?
Must have imagined it?
It doesn't say in the above extracts how it was established MoD did not get the information. Is this an allegation by MoD, or has MB accepted it as true? All the MB guy has said is he wasn't there at the time, which is not the same as admitting the info was not passed on.
It would certainly be a handy "out" for MoD if true. But in my experience, in that period, it is equally, if not more, likely that MB has passed on the info properly and it has not been disseminated correctly; largely because the mechanism was run down in the period 1990-on. Bear in mind the same system allowed captured Argentine publications and maintenance data to be used on Chinook, which says it all.
The key process is one of informing "affected parties", and any reputable company keeps this data up to date and permanently embedded in the necessary "advice notes", or whatever. For example, in a MF714/5. The MoD department that oversaw and policed this fundamental airworthiness principle was disbanded in June 1993, and not replaced in any shape or form. Thereafter, it became pot luck whether the Engineering Authority, Pubs Authority or Project Manager was on the ball. As Mortmeister correctly implies, some would know and others wouldn't.
Even if, somehow, MoD was left off distribution, so critical was the issue that MoD's resident QAR would be climbing all over them. That is, if it happened before these posts were cancelled as a savings measure.
There is a lot more to this but I'm certain the MoD won't trot out any witness who can dissect the issue, and the Coroner won't know what to ask.
It would certainly be a handy "out" for MoD if true. But in my experience, in that period, it is equally, if not more, likely that MB has passed on the info properly and it has not been disseminated correctly; largely because the mechanism was run down in the period 1990-on. Bear in mind the same system allowed captured Argentine publications and maintenance data to be used on Chinook, which says it all.
The key process is one of informing "affected parties", and any reputable company keeps this data up to date and permanently embedded in the necessary "advice notes", or whatever. For example, in a MF714/5. The MoD department that oversaw and policed this fundamental airworthiness principle was disbanded in June 1993, and not replaced in any shape or form. Thereafter, it became pot luck whether the Engineering Authority, Pubs Authority or Project Manager was on the ball. As Mortmeister correctly implies, some would know and others wouldn't.
Even if, somehow, MoD was left off distribution, so critical was the issue that MoD's resident QAR would be climbing all over them. That is, if it happened before these posts were cancelled as a savings measure.
There is a lot more to this but I'm certain the MoD won't trot out any witness who can dissect the issue, and the Coroner won't know what to ask.
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Mort,
Words are easily confused. Did you leave "only" one and a half threads or "at least" one and a half threads.
As a teenager my dad gave me his 1950s fitters notes (AP****) I still have them in the garage. I am guessing that we are of an age where we take our basic training for granted and don't need telling the obvious.
The number of threads protruding is no indication of the tension in the bolt.
I saw a description of the bolt in an earlier post describing a thin head. implies a sheer bolt. years back it was more normal for these to have castle nuts and spilt pins rather than the stiffnuts shown in the pictures in todays BBC video. In this case they should allow the assembly to rotate freely. difficulty torque tightening stiffnuts. particularly if they were reused. heard a number of myths in my time over how many times they could be reused anyway. just chuck them and use new each time for the sake of a few pence.
No one has said if these are standard AGS/BS items. Martin Baker had the habit of issuing their own part numbers for standard bits anyway.
Sad affair. lets hope they come clean and get to the bottom of the problem and share the findings so lessons can be learned.
reading the transcript I wonder why Mr Cameron [of MB not the other one] feels the need to defend Himself by saying it was before his time rather than just present the evidence or give his expert opinion.
Words are easily confused. Did you leave "only" one and a half threads or "at least" one and a half threads.
As a teenager my dad gave me his 1950s fitters notes (AP****) I still have them in the garage. I am guessing that we are of an age where we take our basic training for granted and don't need telling the obvious.
The number of threads protruding is no indication of the tension in the bolt.
I saw a description of the bolt in an earlier post describing a thin head. implies a sheer bolt. years back it was more normal for these to have castle nuts and spilt pins rather than the stiffnuts shown in the pictures in todays BBC video. In this case they should allow the assembly to rotate freely. difficulty torque tightening stiffnuts. particularly if they were reused. heard a number of myths in my time over how many times they could be reused anyway. just chuck them and use new each time for the sake of a few pence.
No one has said if these are standard AGS/BS items. Martin Baker had the habit of issuing their own part numbers for standard bits anyway.
Sad affair. lets hope they come clean and get to the bottom of the problem and share the findings so lessons can be learned.
reading the transcript I wonder why Mr Cameron [of MB not the other one] feels the need to defend Himself by saying it was before his time rather than just present the evidence or give his expert opinion.
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Just an old airframe guy here, but with 'Fork ends' etc where one had to avoid 'Squeezing' a shouldered bolt would always be used.
Basic stuff which could be finely machined to suit the apparatus. I just don't get the ordinary bolt being tightened to a certain level on something which is supposed to move.
Not my speciality, but it makes me think.
Basic stuff which could be finely machined to suit the apparatus. I just don't get the ordinary bolt being tightened to a certain level on something which is supposed to move.
Not my speciality, but it makes me think.
My question is what was the reason for issuing this info to these customers? Was there an accident or something found with these customers ? Only Finland had Hawks with MK10 seat. Others had Mirages/Hunters/Canberras with earlier MB seats.
Drag artist,
We were instructed to do the stiff nut up to only allow 1 1/2 threads showing (ie achieve locking), but crucially ensure that the scissor shackle remained loose.
When tightening the nut, it is true that the base of the bolt was thin and that holding it with a spanner was difficult until you had mastered the correct way of achieving this.
You have hinted at a valid point though, how much engineering training do SAC weapons guys get these days? Don't forget, ejection seat work used to be carried out by Junior Techs as a minimum and is now done by SAC Techs. There may be something there, but I would not like to cast doubt on the tradesmen doing the job, as I have no experience of current standards. However, this critical link would be checked on vitals by the supervisor and independents by an SNCO.
We were instructed to do the stiff nut up to only allow 1 1/2 threads showing (ie achieve locking), but crucially ensure that the scissor shackle remained loose.
When tightening the nut, it is true that the base of the bolt was thin and that holding it with a spanner was difficult until you had mastered the correct way of achieving this.
You have hinted at a valid point though, how much engineering training do SAC weapons guys get these days? Don't forget, ejection seat work used to be carried out by Junior Techs as a minimum and is now done by SAC Techs. There may be something there, but I would not like to cast doubt on the tradesmen doing the job, as I have no experience of current standards. However, this critical link would be checked on vitals by the supervisor and independents by an SNCO.
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Murphy's law is an adage that is typically stated as: Anything that can go wrong, will go wrong.
Originally Posted by Mortmeister
We were instructed to do the stiff nut up to only allow 1 1/2 threads showing...
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Mort, Don't wish to enter a willy waving contest over bolts. Your way would mean that the overall bolt length and also the thickness of the nut was extremely critical. too long bolt- too thin nut and it would float. too short bolt and too thick nut, insistent one and a half threads that could be two; could pinch. The critical test would be the rotation rather than the number of threads protruding.
I only did just over 35 years including 14 as the EA for some similar kit. I worked with Martin Lowe for a spell. I certainly noted the erosion of engineering support staff over the years in that team. Under his name sake The safety managers post migrated to become some sort of Business Manger. even became manned by a blanket stacker shortly afterwards (a fine one mind). The guys down in the old billet blocks at Wyton who came from CSDE etc were disbanded. the posts were supposed to be absorbed by the IPTs but no one wanted the head count on the MCT
Contrary to what Tuc states about 714/715 we continued to use the forms and process well into the mid 2000s, probably at the insistence of the last Gp Capt IPTL* we had. Including completing all the Cost and Brief sheets and providing the safety argument with evidence to support his signature on the Mod.
* Great bloke went on to do something in swimming.
As Tuc also states we would have had a RPO or at least a VPO/ PDS officer and the DGDQA support who would turn up like clock work to LTCs/ Mods Ctee/PDS meetings etc. They would know the kit intimately. I figure we leaned so far we fell over. And the consequences... well we spend so long reminding ourselves about them on here.
It would not really be right for me to comment on the skills of these SAC Techs over JTs working on this kit. however in my line of business (not bang seats) I certainly noted an erosion in skills and competence over the years manifesting itself in lost sorties, incomplete and broken kit, some very poor husbandry. I made myself very unpopular grumbling about it for over 30 years. Pleased to be away from it in some ways. Now I am consumed by the build up of struvite in pumps. Could not be further away from planes.
I only did just over 35 years including 14 as the EA for some similar kit. I worked with Martin Lowe for a spell. I certainly noted the erosion of engineering support staff over the years in that team. Under his name sake The safety managers post migrated to become some sort of Business Manger. even became manned by a blanket stacker shortly afterwards (a fine one mind). The guys down in the old billet blocks at Wyton who came from CSDE etc were disbanded. the posts were supposed to be absorbed by the IPTs but no one wanted the head count on the MCT
Contrary to what Tuc states about 714/715 we continued to use the forms and process well into the mid 2000s, probably at the insistence of the last Gp Capt IPTL* we had. Including completing all the Cost and Brief sheets and providing the safety argument with evidence to support his signature on the Mod.
* Great bloke went on to do something in swimming.
As Tuc also states we would have had a RPO or at least a VPO/ PDS officer and the DGDQA support who would turn up like clock work to LTCs/ Mods Ctee/PDS meetings etc. They would know the kit intimately. I figure we leaned so far we fell over. And the consequences... well we spend so long reminding ourselves about them on here.
It would not really be right for me to comment on the skills of these SAC Techs over JTs working on this kit. however in my line of business (not bang seats) I certainly noted an erosion in skills and competence over the years manifesting itself in lost sorties, incomplete and broken kit, some very poor husbandry. I made myself very unpopular grumbling about it for over 30 years. Pleased to be away from it in some ways. Now I am consumed by the build up of struvite in pumps. Could not be further away from planes.
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Murphy's Law has no place anywhere near ejection seats. It's been a few years since I was working on Tornado F3s as an Airframe Technician, but the reverence with which the seats and associated systems are treated by the groundcrew should not be underestimated.
I would seriously doubt that the tightening of a scissor shackle bolt would be the last stage of seat servicing in a bay. Whilst I would not wish to pre-empt any coroner's findings, I would be shocked if it turned out that the scissor shackle bolt had been tightened to the extent that it was the only thing preventing the parachute deploying.
The cause of the ejection sequence itself will hopefully be revealed, and lessons learned.
I would seriously doubt that the tightening of a scissor shackle bolt would be the last stage of seat servicing in a bay. Whilst I would not wish to pre-empt any coroner's findings, I would be shocked if it turned out that the scissor shackle bolt had been tightened to the extent that it was the only thing preventing the parachute deploying.
The cause of the ejection sequence itself will hopefully be revealed, and lessons learned.
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The second quote in Note #85 suggests someone has found several ways to inadvertently fire the seat though surely it would have happened before now if it was possible?
I've seen no mention of the state of the seat pins, or any suggestion at what Flt Lt Cunningham might have been doing at that moment or what stage he was at in the start up sequence.
I've seen no mention of the state of the seat pins, or any suggestion at what Flt Lt Cunningham might have been doing at that moment or what stage he was at in the start up sequence.
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WRT the M B witness' "I don't know, I wasn't there"....
As others have hinted (or maybe i read something into it)
the man works for MB
MOD is obviously an important customer
there are other Bang-seat manufacturers
anyone in MOD who may bear a responsibility for poor systems/safety procedures, may also have influence in specifications for purchasing.
To put it bluntly....the MB staff are going to be somewhat circumspect when it comes to rocking the boat...they are unlikely to deliberately cause a major embarassment to one of their major profit-sources.
Motor-car seat-belt mountings, by numbers, have far more events than bang-seats...one does not hear of fatal crashe caused by seat-belt failure....where fittings have to have movement, there are stepped bushes / shouldered bolts/ spring-washers /fibre washers to ensure that, according to design and purpose, a belt can be removed/checked/refitted by a relatively unskilled person
yes, some designs have a very thin head on a stepped bolt...they get dogged-up tight...if the retained part is meant to move, it does..if it's meant to be rigidly fixed, it is.
there's a whiff of arse and back-covering here, IMO.
As others have hinted (or maybe i read something into it)
the man works for MB
MOD is obviously an important customer
there are other Bang-seat manufacturers
anyone in MOD who may bear a responsibility for poor systems/safety procedures, may also have influence in specifications for purchasing.
To put it bluntly....the MB staff are going to be somewhat circumspect when it comes to rocking the boat...they are unlikely to deliberately cause a major embarassment to one of their major profit-sources.
Motor-car seat-belt mountings, by numbers, have far more events than bang-seats...one does not hear of fatal crashe caused by seat-belt failure....where fittings have to have movement, there are stepped bushes / shouldered bolts/ spring-washers /fibre washers to ensure that, according to design and purpose, a belt can be removed/checked/refitted by a relatively unskilled person
yes, some designs have a very thin head on a stepped bolt...they get dogged-up tight...if the retained part is meant to move, it does..if it's meant to be rigidly fixed, it is.
there's a whiff of arse and back-covering here, IMO.