Flt. Lt. Sean Cunningham inquest
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I must admit, when they initially realised there was a problem you would think they would have warned all the operators immediately and redesigned the bolt as a matter of urgency.
I can understand the visible thread issues, but I don't know, maybe there is a clearance problem with getting a torque wrench in, hence using visible thread as a guide...
Sadly this also deflects from the issue of why the seat fired.... That needs to be addressed because it's not just an issue when the seat is needed, but an issue when anyone accesses the cockpit.
I can understand the visible thread issues, but I don't know, maybe there is a clearance problem with getting a torque wrench in, hence using visible thread as a guide...
Sadly this also deflects from the issue of why the seat fired.... That needs to be addressed because it's not just an issue when the seat is needed, but an issue when anyone accesses the cockpit.
Yes to my eye there are two issues here, the overtightening of the bolt and why the seat fired in the first place.....
I have a theory but I don't want to add any fuel to any fires....
I have a theory but I don't want to add any fuel to any fires....
Contrary to what Tuc states about 714/715 we continued to use the forms and process well into the mid 2000s
The process for ensuring independent scrutiny and approval of 714s was disbanded by the Chief Engineer in June 1993. I chaired the last avionics committee. At the same time, he stopped routine updates and maintenance of MoD's equivalent databases e.g. the Avionics List, which was how MoD staff found out what was fitted to what platform. He introduced "self assessment and approval" which, because it ran contrary to SoS's and PUS's mandated requirement for independent scrutiny, is why the relevant regulations were never updated; D/Stan couldn't find anyone to put their name to a policy that contradicted SoS or PUS. In the end, they gave up and the Def Stan was cancelled without replacement (yet is still mandated, despite MoD no longer having a single copy!) Hope that clarifies.
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Maybe the pin wasn't put backin place after its last flight, despite engineers servicing the jet during the period until the next flight, the error wasn't picked up. Maybe subsequently the straps were caught around the handle when he strapped in.
Maybe MB were aware that there was a problem with that part having been picked up on other ejections albeit forward speed ones so the seat worked on those occasions but a zero zero ejection may have been a issue. Maybe MB didn't warn of this issue. Who knows - it can be a murky world protecting corporate images.
Just my thoughts having screwed up myself with the pin during training. I was physically sick when I realised what I had done.
Maybe MB were aware that there was a problem with that part having been picked up on other ejections albeit forward speed ones so the seat worked on those occasions but a zero zero ejection may have been a issue. Maybe MB didn't warn of this issue. Who knows - it can be a murky world protecting corporate images.
Just my thoughts having screwed up myself with the pin during training. I was physically sick when I realised what I had done.
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These seats are designed to work at zero-zero.
It is likely that Flt Lt Cunningham was fully strapped in when the seat fired.
Given how important and how much it is drummed into everyone about ensuring the seat is made safe and enabled you would have thought it was very unlikely that the seat would accidently fire in normal everyday circumstances.
The Taylor-Scott accident put a focus on ensuring the seats could not be activated by objects falling beneath the seats - at least on Harriers IIs and I presume all other similar designs?
It is likely that Flt Lt Cunningham was fully strapped in when the seat fired.
Given how important and how much it is drummed into everyone about ensuring the seat is made safe and enabled you would have thought it was very unlikely that the seat would accidently fire in normal everyday circumstances.
The Taylor-Scott accident put a focus on ensuring the seats could not be activated by objects falling beneath the seats - at least on Harriers IIs and I presume all other similar designs?
If the nut is tightened correctly (leaving 1 1/2 threads visible) the scissor shackle fits perfectly. If you overtighten the nut the scissor shackle gets compressed and that is what some of us feel is the issue here.
Yes, a shouldered bolt would potentially prevent this, but it would be up to the boffins at M-B to analise and sanction that kind of change. They may well have had their reasons for using this assembly. To be honest, the basic design of that assembly had not altered much over many years and I understand Typhoon and Lightning II seats are significantly different in this area.
Just to inform, this operation would not be carried out in a Seat Bay, but would have been carried out by 1st line armourers during the act of fitting the parachute headbox.
For what its worth, I would still rather have a M-B seat than any other!
Yes, a shouldered bolt would potentially prevent this, but it would be up to the boffins at M-B to analise and sanction that kind of change. They may well have had their reasons for using this assembly. To be honest, the basic design of that assembly had not altered much over many years and I understand Typhoon and Lightning II seats are significantly different in this area.
Just to inform, this operation would not be carried out in a Seat Bay, but would have been carried out by 1st line armourers during the act of fitting the parachute headbox.
For what its worth, I would still rather have a M-B seat than any other!
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Given how important and how much it is drummed into everyone about ensuring the seat is made safe and enabled you would have thought it was very unlikely that the seat would accidently fire in normal everyday circumstances.
Mistakes happen.
Originally Posted by Mortmeister
If the nut is tightened correctly (leaving 1 1/2 threads visible) the scissor shackle fits perfectly.
The 1990 warning, which was not sent to the MoD, specified that the drogue shackle nut should not be over-tightened. Michael Cameron, after sales executive for Martin Baker, told the inquest that the issue of over-tightening of the nut was a potential risk to life. He admitted that the company should have made it clear to its customers what the problem was.
Mr Cameron, who served in the RAF for over 20 years before joining Martin Baker, said "I don't know what happened at the time."
The inquest has heard how aircraft manufacturers British Aerospace and McDonnell Douglas had raised concerns about the issue which was discovered during the assembly of Tornado jets.
Mr Cameron said the nut should be fitted so that it was "flush" with the bolt rather than having one and a half threads showing as written in the manufacturer's manual at the time.
Mr Cameron, who served in the RAF for over 20 years before joining Martin Baker, said "I don't know what happened at the time."
The inquest has heard how aircraft manufacturers British Aerospace and McDonnell Douglas had raised concerns about the issue which was discovered during the assembly of Tornado jets.
Mr Cameron said the nut should be fitted so that it was "flush" with the bolt rather than having one and a half threads showing as written in the manufacturer's manual at the time.
JTO,
Having been away from this equipment for some years now, I cannot comment on the publications as they are today. All I have stated comes from memory, having not seen a Mk10 Seat AP for over 14 years.
I'm at a loss to think of another explanation for what happened. The Mk10 seat was/is very reliable, with an excellent track record.
Having been away from this equipment for some years now, I cannot comment on the publications as they are today. All I have stated comes from memory, having not seen a Mk10 Seat AP for over 14 years.
I'm at a loss to think of another explanation for what happened. The Mk10 seat was/is very reliable, with an excellent track record.
Mort, I understand entirely but is there is a chance that you, like many others, were over-tightening the bolt to expose 1 1/2 threads because that is exactly what the incorrect maintenance manual asked you to do?
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Dragartist
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.
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.
Something is wrong here, when I was taught about nuts and bolts and the torquing and locking of same, the 1.5 pitches of thread was a fundamental rule not a specific, one off, manufacturers requirement. In other words if when any nut was tightened, if there weren't 1.5 pitches of the thread exposed, then the bolt was too short. I really can't see someone like M.B. requiring a nut surface to be flush with bolt end and therefore going against a basic engineering principal.
JTO,
I do not believe so, as once the bolt was secure through the Scissor Shackle and the Shackle attaching it to the Drogue Withdrawal Line there was always freedom of movement of the Withdrawal Line Shackle. If the Nut was too tight, the Withdrawal Shackle would compress around the Scissor Shackle and be stiff to move. The whole assembly was then secured with a string tie attached to the closure pin in the Parachute head box.
I do not believe so, as once the bolt was secure through the Scissor Shackle and the Shackle attaching it to the Drogue Withdrawal Line there was always freedom of movement of the Withdrawal Line Shackle. If the Nut was too tight, the Withdrawal Shackle would compress around the Scissor Shackle and be stiff to move. The whole assembly was then secured with a string tie attached to the closure pin in the Parachute head box.
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The 1 1/2 to 3 threads is a generic statement. If the AMM / CMM states other dimensions or loadings, that statement shouldn't be used as the definitive direction. Same sort of thing happened with a Mk 10 TLP in 2007.. Not one of the best weeks I ever had (and I had it easy to the three people who signed the MMPs).
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Having spent many years fitting seats at Saints during the 90's I like Mort recall the 1 1/2 threads on the scissor shackle and at times it was a struggle to achieve that but there was always freedom of movement, which I am pretty sure had to be checked for during vitals or indies, the MK10 seats were also fitted to the Sea Harrier.
As to what caused the initial firing of the seat, I recall an incident at Saints were I was called to a Hawk where the pilot was strapping in for a test flight after maintenance, I dont recall the initial reason why I was called but what I saw sent a shiver down the spine! the QRF box was through the seat pan firing handle and the pilot had strapped in not realising, the pin was still fitted but had he lent forward to remove it then then sat back would it have been enough to pull the handle? not sure, just glad we never found out.
As to what caused the initial firing of the seat, I recall an incident at Saints were I was called to a Hawk where the pilot was strapping in for a test flight after maintenance, I dont recall the initial reason why I was called but what I saw sent a shiver down the spine! the QRF box was through the seat pan firing handle and the pilot had strapped in not realising, the pin was still fitted but had he lent forward to remove it then then sat back would it have been enough to pull the handle? not sure, just glad we never found out.
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One of the best things I remember about the RAF, was that engineering officers & pilots would always give time to those on the 'Coal face'.
To blindly follow the 'Book' without question, written by those far removed, is a potentially dangerous thing.
Disregarding the book is dangerous for sure, but there has to be a two way communication.
Experience does count & unbelievable things do happen.
I still scratch my head & wonder why MB chose to use a non shouldered bolt on a scissor shackle.
To blindly follow the 'Book' without question, written by those far removed, is a potentially dangerous thing.
Disregarding the book is dangerous for sure, but there has to be a two way communication.
Experience does count & unbelievable things do happen.
I still scratch my head & wonder why MB chose to use a non shouldered bolt on a scissor shackle.
I may have missed it in an earlier post, but does anyone know if the firing handle was found to be out of the normal position when the seat was found, or if any abnormal harness routings were noted.
I still find it very hard to believe that regardless of any bolt thread "show" requirement that this assembly COULD be overtightened as every engineer working on the seat would most surely know how the scissor shackle was meant to function.
Or how anyone would enter a jet cockpit without first positively ensuring that the seat firing handle(s) and safety pin(s) were in position, so surely all must have looked absolutely normal as he boarded the jet.
This really is a most curious accident.
I still find it very hard to believe that regardless of any bolt thread "show" requirement that this assembly COULD be overtightened as every engineer working on the seat would most surely know how the scissor shackle was meant to function.
Or how anyone would enter a jet cockpit without first positively ensuring that the seat firing handle(s) and safety pin(s) were in position, so surely all must have looked absolutely normal as he boarded the jet.
This really is a most curious accident.
Last edited by RetiredBA/BY; 23rd Jan 2014 at 09:22.
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I still scratch my head & wonder why MB chose to use a non shouldered bolt on a scissor shackle.
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Sorry Tuc, did not mean any offence. must read more carefully next time.
the 714/5 process per 05-123 was sound. I saw it watered down in later years. each team appeared to want to devise their own process.
when I spent a bit of time in DD2 area DDSM6 we were very big on cross fertilisation. Unfortunatly the formation of IPTs and Business units knocked a lot of this on the head. there was a lot of corparate knowlege around RAE/DERA/and early Q2. Some may have said they were the consistency*. There attendance at LTCs was knocked on the head by the bean counters (yes I have to admit I may have been slightly guilty in going along with this rather than digging my heals in).
* I don't feel this is the case today however.
Same was true of the F765 process. This is where the folks at Kentigern came into their own. we had a real good guy. (and yes I did put him forward for an award after they were dispanded)
One comment re secondary references and NATO numbers - I agree with the comments made by Cobalt. This would be the case in an ideal world with competant people serving the department rather than their employer. My comments were based on my own real world experiences.
I do hope the truth comes out soon. By the sound of proceedings I fear that this just culture being banded about has been put back in the bottom drawer. I do hope I am wrong..... again
the 714/5 process per 05-123 was sound. I saw it watered down in later years. each team appeared to want to devise their own process.
when I spent a bit of time in DD2 area DDSM6 we were very big on cross fertilisation. Unfortunatly the formation of IPTs and Business units knocked a lot of this on the head. there was a lot of corparate knowlege around RAE/DERA/and early Q2. Some may have said they were the consistency*. There attendance at LTCs was knocked on the head by the bean counters (yes I have to admit I may have been slightly guilty in going along with this rather than digging my heals in).
* I don't feel this is the case today however.
Same was true of the F765 process. This is where the folks at Kentigern came into their own. we had a real good guy. (and yes I did put him forward for an award after they were dispanded)
One comment re secondary references and NATO numbers - I agree with the comments made by Cobalt. This would be the case in an ideal world with competant people serving the department rather than their employer. My comments were based on my own real world experiences.
I do hope the truth comes out soon. By the sound of proceedings I fear that this just culture being banded about has been put back in the bottom drawer. I do hope I am wrong..... again