From yesterdays Lincolnshire Echo:
Here
As important nuts and bolts go, this is an important one. Is it really true there was no torque guidance in the manuals...?
Maintenance instructions for Red Arrows ground crew working on ejection seats gave them no proper guidelines on a crucial nut and bolt.
When ejection seats are fired a drogue parachute deploys in order to stabilise the descent.
This mechanism then allows the main parachute to release.
When the pilot activates the seat, a plunger releases the arm of a scissor shackle and in turn releases the drogue shackle the first chute is attached to.
It is crucial that the nut and bolt through shackles is not over-tightened, which could prevent it working properly.
Questions over the bolt's performance were raised during the inquest into the death of Flight Lieutenant Sean Cunningham.
He died on November 8, 2011 after his ejection seat was fired while his plane was on the ground at RAF Scampton.
Reds armourer Sergeant Chris Clarkson, who was present when Flt Lt Cunningham ejected, but has since left the RAF, told the court he understood the drogue nut and bolt should be tightened to a “good positive lock” and showing at least one and a half threads.
He said: “The head of the bolt is very thin.
“It’s difficult to get the spanner on it especially with it’s location on the under side of the drogue.”
Hugh Davies, QC, for Lincolnshire Police, asked: “Did you understand that if the nut was tightened too far it would prevent eventual release?”
Mr Clarkson replied: “I was not aware of that at all.”
Bernard Thorogood, counsel for the Health and Safety Executive, read this extract from the workshop manual that guided the armourers: “Pass the bolt through the drogue and scissor shackles and secure with a lock nut.”
He told the court: “In the absence of any more direct instructions such as torque, that’s the instructions that mechanics or armourers would follow.
“That’s what brings us to think about one and a half turns as a basic engineering principle.
“The problem with that sort of instruction is it involves a subjective amount of judgment by whoever is tightening the bolt.”
The inquest continues.
Mr Clarkson said he did appreciate that when an ejection seat fires the drogue needs to separate from the scissor shackle.
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