Flt. Lt. Sean Cunningham inquest
as a mere Metman, what is 1/2 a thread ....... I am not an engineer so .......?
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Langley,
I guess like me you are feet and inches man. In this context they are talking about the thread pitch or peak to peak measurement. so say we have a 1/4" diameter bolt which has a thread of say 20 threads per inch then the pitch would be 50 thousands of in inch.
to have the standard one and a half threads poking through the nut would be 75 thou. Now 62 and a half thou is one 16th of an inch.
As you can imagine there is a tollerance on all the things. In general terms we look to have a minimum of one and a half threads poking through and may accosiate this with the term "in safety"
Now in this particular case the one and half threads appears to have become presciptive. (as a measure of the tightness. This is not good)
Imagine turning the nut through another half turn to achive this presciption. this would mean moving it 25 thou and may distort the shackle.
I can do mm as well but most aircraft of our generation use engilish/american measurements.
There are one or two with a mixture. French helicopters were problematic for me. we did a number of modifications and could not get the hardware. every Enlish bolt had a label stuck besides it. with special dispensation. It is so important to get the right bits. I even had a case on the Nimrod with some Oxygen fittings that had metric screws! It could be disasterous.
Hope this helps
I am sure you are a good met man.
I guess like me you are feet and inches man. In this context they are talking about the thread pitch or peak to peak measurement. so say we have a 1/4" diameter bolt which has a thread of say 20 threads per inch then the pitch would be 50 thousands of in inch.
to have the standard one and a half threads poking through the nut would be 75 thou. Now 62 and a half thou is one 16th of an inch.
As you can imagine there is a tollerance on all the things. In general terms we look to have a minimum of one and a half threads poking through and may accosiate this with the term "in safety"
Now in this particular case the one and half threads appears to have become presciptive. (as a measure of the tightness. This is not good)
Imagine turning the nut through another half turn to achive this presciption. this would mean moving it 25 thou and may distort the shackle.
I can do mm as well but most aircraft of our generation use engilish/american measurements.
There are one or two with a mixture. French helicopters were problematic for me. we did a number of modifications and could not get the hardware. every Enlish bolt had a label stuck besides it. with special dispensation. It is so important to get the right bits. I even had a case on the Nimrod with some Oxygen fittings that had metric screws! It could be disasterous.
Hope this helps
I am sure you are a good met man.
I still remember the Westland Split pin holes, that must have been drilled from both sides or offset as they would line up one side, but not the other.
Then it happened again.......
dragartist
French helicopters were problematic for me.
I recall, 40 years ago, an Admiral being impressed with my French as I was apparently repairing a Gazelle clutch with my sole reference being a French drawing. We kept the translation in a drawer. At least we had an audit trail to our standard of clutch, unlike the Argie Chinook pubs used by the RAF.
Excellent summary of Imperial threads. My memory tells me there is a Def Stan on your labels, especially a warning of Unified threads. I'd still want to know if the nut in this case had been re-used, as that is a common reason for over-tightening. If such questions had been asked I'm sure the local journalist would have twigged its importance. What we're reading at the moment is a series of unchallenged and increasingly ludicrous MoD statements.
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I was somewhat surprised (to say the least) to read in The Telegraph today that " a military investigation . . . had earlier concluded that the way pilots were selected for [the Red Arrows] could also have been a factor . . . the choice of pilots was 'heavily weighted' to how they would fit into the team rather than flying ability".
So, in summary, some Red Arrows pilots are not quite top notch, therefor increasing the likelihood if an accident happening with an ejector seat.
That's surely got to be the biggest load of bollox, no? Why would "a military investigation" come to such a ridiculous conclusion?
I'm staggered. What am I missing?
So, in summary, some Red Arrows pilots are not quite top notch, therefor increasing the likelihood if an accident happening with an ejector seat.
That's surely got to be the biggest load of bollox, no? Why would "a military investigation" come to such a ridiculous conclusion?
I'm staggered. What am I missing?
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If it is identified that a lot of rules and regulations are contravened, then a military investigation may choose to ask why noone has either picked the contraventions up, or why noone (within the group of people) felt they should speak up to change the culture. If the group of people are self-selected (i.e. people who would fit in) then it is unlikely that they would even identify the issue, or be likely to raise them.
Seems perfectly understandable to question how things are done when they are so different to the rest of the military selection processes...reading the Telegraph article.
Seems perfectly understandable to question how things are done when they are so different to the rest of the military selection processes...reading the Telegraph article.
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the choice of pilots was 'heavily weighted' to how they would fit into the team rather than flying ability".
I believe the minimum standard is "above average", which when you are talking about such a small group of highly trained professionals to select from in the first place, means the article does appear to be a bit.....well......
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Good picture Nutty, I wish I was clever enough to insert graphics (or extracts from my Dads 1950s trade training notes!) Now then is that one or two threads poking though? I rest my case M'laud.
Tuc, yes three Olympic type rings (I'd be guessing at Def Stan 05-40 I could probably have written chapter 400 of 00-970!) now there was no standard for identifying metric threads on English aircraft so they were labelled "Metric" This was in the extreme only where proprietary items had to be used.
I was dead worried about the unified fixings on the Gazelle as some were blind threaded holes in potted inserts into the nomex honeycomb structures. There may have been a couple on the Lynx and Puma as well.
Now you will know the Nimrod had mostly BA/BSF on the airframe, all our racks were unified. the later avionics were Metric post about 1980. can't remember if the Starwindow stuff from America was metric. I would probably have had discussions on the topic. the problem was metric hardware to aircraft standard with metallic locking elements was as rare as rocking horse droppings back then. Getting hold of stuff from the Jaguar, Tonka or even Sea Eagle Missile was an issue.
I certainly remember the Argentine CH47 at Wroughton. I thought it only got used for BDR training. We had the pylon at JATE for a spell when we were devising transport dollies. I wonder how they went on with the A109s
Apologies for the tread drift. just expanding on a few points and illustrating scope for Mr Murphy coming home to roost.
Tuc, yes three Olympic type rings (I'd be guessing at Def Stan 05-40 I could probably have written chapter 400 of 00-970!) now there was no standard for identifying metric threads on English aircraft so they were labelled "Metric" This was in the extreme only where proprietary items had to be used.
I was dead worried about the unified fixings on the Gazelle as some were blind threaded holes in potted inserts into the nomex honeycomb structures. There may have been a couple on the Lynx and Puma as well.
Now you will know the Nimrod had mostly BA/BSF on the airframe, all our racks were unified. the later avionics were Metric post about 1980. can't remember if the Starwindow stuff from America was metric. I would probably have had discussions on the topic. the problem was metric hardware to aircraft standard with metallic locking elements was as rare as rocking horse droppings back then. Getting hold of stuff from the Jaguar, Tonka or even Sea Eagle Missile was an issue.
I certainly remember the Argentine CH47 at Wroughton. I thought it only got used for BDR training. We had the pylon at JATE for a spell when we were devising transport dollies. I wonder how they went on with the A109s
Apologies for the tread drift. just expanding on a few points and illustrating scope for Mr Murphy coming home to roost.
On the selection issue, the irony is that Sean's intake year was more "diverse" than preceding years because it was the first for a while that wasn't dominated by ex-creamie QFIs of a particular vintage. It even included 2 GR4 pilots! The suggestion of cliqueyness in selection over the preceding period is particularly uncomfortable reading because both the Crete and Bournemouth accidents can be cast in the light of 'risky shift' in a closed-shop elite. I wonder how much significance will be attached to the fact that Red 1 for the period in question had been promoted directly from the team and had not spent time away as per the current incumbent.
It saddens me that the display flying world is still battling these issues many years on from Kemble, Ramstein, Fairchild, Elmendorf... one would have thought that enough case studies existed by now
It saddens me that the display flying world is still battling these issues many years on from Kemble, Ramstein, Fairchild, Elmendorf... one would have thought that enough case studies existed by now
Last edited by Easy Street; 24th Jan 2014 at 20:01.
On the MB 'no design fault' notice, you need to read it with lawyerly attention to detail (my bold):
They are not denying that a design fault (eg in the handle or safety pin) might have caused the ejection. However, since the ejection should have been survivable, the fatality was due to the failure of the parachute to deploy. As soon as the over-tightened bolt was discovered, therefore, MB could issue that statement to reassure their customers without needing to establish why the ejection had happened in the first place.
Now, one for the accident investigators among you. A service inquiry is required for major injuries. If Sean's parachute had deployed, it is still quite possible that he would have broken a few bones and precipitated an SI. The cause of that accident would be the pulling of the seat handle, with its unsafe condition as a contributory factor. Given that the outcome was worse, ie fatal, does that make the over-tightening of the shackle bolt an aggravating factor to the same root causes? Or is the over-tightening of the shackle bolt now the cause of the accident, with the unsafe condition of the handle and its pulling as contributory factors? And would the distinction have any significance for liability or culpability?
satisfied that neither a mechanical nor a design fault were to blame for the fatality
Now, one for the accident investigators among you. A service inquiry is required for major injuries. If Sean's parachute had deployed, it is still quite possible that he would have broken a few bones and precipitated an SI. The cause of that accident would be the pulling of the seat handle, with its unsafe condition as a contributory factor. Given that the outcome was worse, ie fatal, does that make the over-tightening of the shackle bolt an aggravating factor to the same root causes? Or is the over-tightening of the shackle bolt now the cause of the accident, with the unsafe condition of the handle and its pulling as contributory factors? And would the distinction have any significance for liability or culpability?
Last edited by Easy Street; 24th Jan 2014 at 20:11.
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Excuse me for butting in again, I'm just wondering about the workings of the modern ejector seats. How far does the seat pan handle have to move before firing the seat?
From my non specialist point of view, it would seem sensible to have a movement of an inch or so, which would make it quite obvious to those entering the cockpit, rather than a 'Hair trigger' type of thing.
I'm as baffled as anyone else, yet have over 35 years of 'Hands on' aircraft experience.
From my non specialist point of view, it would seem sensible to have a movement of an inch or so, which would make it quite obvious to those entering the cockpit, rather than a 'Hair trigger' type of thing.
I'm as baffled as anyone else, yet have over 35 years of 'Hands on' aircraft experience.
The pull is of the order of an inch (a little more if anything) and about 30-40lb force. The issue appears to be that the handle had been inadvertently pulled most of the way through some as-yet unstated means on the previous sortie, leaving it on something close to a hair trigger.
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does that make the over-tightening of the shackle bolt an aggravating factor to the same root causes?
Or is the over-tightening of the shackle bolt now the cause of the accident
unsafe condition of the handle and its pulling as contributory factors
And would the distinction have any significance for liability or culpability?
Just my irrelevant views as I'm not a SME.
Excuse me for butting in again, I'm just wondering about the workings of the modern ejector seats. How far does the seat pan handle have to move before firing the seat?
So in short - you do have to pull the bang seat handle pretty hard on the Mk 10 seats...
LJ
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I'm still a little amazed that a seat pan handle could be half pulled and the pin fitted.
My tuppence worth is that when you check seat pins you are mostly doing it for your own safety, not then next person's.
Moving seat pins is a different matter, and judging by the BOI Presidents comments, it was Flt Lt Cunningham himself who fitted that pin incorrectly, 4 days previously.
4 days? November? Was this aircraft towed in and out of the hangar with a techie sat in the seat on brakes !
I note a previous posters comment that he had seen a photo of an unsafe seat pan handle and says it is possible, but I am stunned.
Surely an A/F, B/F, T/R on a Hawk would pick this up?
And finally, the last person to check that pin...
My tuppence worth is that when you check seat pins you are mostly doing it for your own safety, not then next person's.
Moving seat pins is a different matter, and judging by the BOI Presidents comments, it was Flt Lt Cunningham himself who fitted that pin incorrectly, 4 days previously.
4 days? November? Was this aircraft towed in and out of the hangar with a techie sat in the seat on brakes !
I note a previous posters comment that he had seen a photo of an unsafe seat pan handle and says it is possible, but I am stunned.
Surely an A/F, B/F, T/R on a Hawk would pick this up?
And finally, the last person to check that pin...
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They are not denying that a design fault (eg in the handle or safety pin) might have caused the ejection. However, since the ejection should have been survivable, the fatality was due to the failure of the parachute to deploy. As soon as the over-tightened bolt was discovered, therefore, MB could issue that statement to reassure their customers without needing to establish why the ejection had happened in the first place.
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Thanks for the steer, I'll wait for the photos.
I was stood next to the Canberra T17 when the armourer Ted T****r(?) fired the seat in the hangar at Wyton in the early 80's. And stood in the bomb bay when the electrician J**n L****t fired the canopy dets. Maybe that's why I'm deaf.
Both incidents had about 4 bits of swiss cheese lining up.
But this must be a world record. Murphy's Law must come into effect after 10 bits of cheese, and this is more than 20 !
I was stood next to the Canberra T17 when the armourer Ted T****r(?) fired the seat in the hangar at Wyton in the early 80's. And stood in the bomb bay when the electrician J**n L****t fired the canopy dets. Maybe that's why I'm deaf.
Both incidents had about 4 bits of swiss cheese lining up.
But this must be a world record. Murphy's Law must come into effect after 10 bits of cheese, and this is more than 20 !
Easy Street is about right with the length and pull required to initiate ejection. Having pulled these handles on many occasions, it is pretty obvious when it is out. Sorry all, but I'm struggling with how this scenario can have been allowed to develop!
The seat pins should have been moved to 'Safe for Maintenance' position and signed/countersigned by the armourers prior to being towed into the hangar after the previous flight. Although the Seat Pan Pin had been fitted by the pilot, the armoured concerned is required to check the correct fitment of that plus the MDC Firing Handle and the MDC Firing Unit Pins (all fitted by the pilot) in each cockpit.
4 days later when towed out, they should have been placed 'Safe for Parking,' again requiring a check of all pins as well as removing the Main Gun, Rocket Initiator and Manual Separation Firing Unit Pins. What happened during the time in the shed the BOI should know from aircraft paperwork.
I have to ask myself, were the armourers adequately manned, trained and experienced or were they overstretched?
The seat pins should have been moved to 'Safe for Maintenance' position and signed/countersigned by the armourers prior to being towed into the hangar after the previous flight. Although the Seat Pan Pin had been fitted by the pilot, the armoured concerned is required to check the correct fitment of that plus the MDC Firing Handle and the MDC Firing Unit Pins (all fitted by the pilot) in each cockpit.
4 days later when towed out, they should have been placed 'Safe for Parking,' again requiring a check of all pins as well as removing the Main Gun, Rocket Initiator and Manual Separation Firing Unit Pins. What happened during the time in the shed the BOI should know from aircraft paperwork.
I have to ask myself, were the armourers adequately manned, trained and experienced or were they overstretched?