For those with a passion for things of a technical nature , please read on.
Taken from the CAA website:
MANDATORY PERMIT DIRECTIVE : 2007-002 BRITISH AEROSPACE.
Subject: Port and Starboard mainplane spar upper attachment lugs cracking.
Applicability: All British Aerospace Jet Provost and Strikemaster aeroplanes.
Reason: Over a number of years, cracking has occurred in the mainplane spar upper attachment lug in the outer surface and also from the bore of the lug. BAe CSI/JET Provosts being promulgated under Revision 2, following a review at BAe). BAeCSI/Strikmaster 50 Issue 3 was mandated by MPD 1995-109 R1 previously on Strikemaster aircraft.
Following a recent accident due to wing structural failure, a review of the above CSIs has been conducted and it has been determined that they do not necessarily find cracking if it takes place from the inner surface of the lug where any crack may be obscured by the bush.
Repeated removal of the bush is not advisable as it may introduce damage to the lug bore.
The consequence of failure of the lug is loss of the aircraft. This MPD is to restrict Strikemaster and Jet Provost operations to ‘non-aerobatic’, so reducing the rate of fatigue damage accumulation and reducing the possibility of severe downward bending loads, which are suspected to be the main contributor to the failure.
This MPD may be alleviated or revised when the CAA are satisfied that alternative methods of crack detection have been determined and defined.
Compliance: Before further flight, insert a placard within plain view of the pilots stating: “Aerobatics are prohibited”.
This MPD becomes effective on 10 March 2007.
By: JDK - 24th March 2007 at 07:50
The Australian Civil Aviation Safety Authority’s Reports on Strikemasters are here.
By: bexWH773 - 24th March 2007 at 07:40
Ive never been a huge fan of the clowns at the CAA, Ive used clowns in place of far stronger and abusive phrases that are sat in my mind (when it comes to preserved aircraft flying again), but in this case I think they have acted correctly,in plain terms translate to “something broke, its not easy to monitor the fatigue, so until its sorted becareful”. Also, unlike other industries, the CAA deal with problems and learn from accidents pretty quickly. I worked in the rail industry for 15 years and rail safety was and still is a joke compared to air safety. Bex
By: bloodnok - 24th March 2007 at 07:02
surely if the problem is a downward force on one of the upper lugs, then that would only occur during negative G manouvers….?
i personally think its a good idea to be cautious, there’s been enough debate on this forum about how much damage is done to the ‘vintage’ aircraft scene by crashes, especially when they happen at airshows. so if this directive stops a JP losing a wing in front of a large crowd, then i think its a good idea.
anyway, its not permanent, as soon as they find a NDT technique that shows the cracks accurately, then this directive will be lifted.
By: OHOPE - 24th March 2007 at 06:44
With one wing found some distance away from the main wreckage , and the type having a history of this problem , I think the correct decision has beeen made .
All the RNZAF Bluntys had their wings redone during their service life here .
By: Easy Tiger - 23rd March 2007 at 23:07
Surely a straight push or pull on the stick will give + or – G without a rate turn or angle of bank!
“At the end of the day, if there is any possibility of a structural failure, then steps need to be taken”.
I couldnt agree more, however structural failure has not been proven and the decision should be an engineering one. How can anyone provide an instant answer when you do not know if there is a problem.:confused:
By: The Blue Max - 23rd March 2007 at 22:34
With all the tens of thousands of hours flown on all marks of JP’s, to put an aerobatic restriction on them and at the same time not restrict the “G” sounds a bit nearsighted. It is not the maneuver that might cause the structural failure, but the stress put on the stucture that might cause it. One might pull 5 or 6 G’s in the break if one wanted to. One could also do a nice roll with very little increas in positive G applied. One is aerobatic, the other is not. What have the Australians done?
i think you need to check on the official meaning of the term Aerobatics! i think you will find, i am happy to be corrected here if i am wrong:) , but i think anything grater than a rate one turn and 45degree’s of bank are officialy classed as Aerobatics!! therefore if you pull 5 or 6 G ( its ‘G’ by the way not G’s) then you would surely exceed this?
It also sound reading the AD that once a reliable NDT inpection is found then the resriction may be lifted. As always were looking on the black side here:rolleyes: At the end of the day if there is any possibility of a structural failure then steps need to be talken, it does seem to be worded badly and a G limit should also be imposed 🙂
By: Easy Tiger - 23rd March 2007 at 21:55
Jo
I would quite happily climb into any JP maintained to the CSI and do as much aeros as you like.
Bear in mind, an aircraft can induce much positive and negative G without doing aeros and also complete much aerobatics with minimal G, so a rather half thought through “solution”.
By: SeaDog - 23rd March 2007 at 21:54
Structural Failure
With all the tens of thousands of hours flown on all marks of JP’s, to put an aerobatic restriction on them and at the same time not restrict the “G” sounds a bit nearsighted. It is not the maneuver that might cause the structural failure, but the stress put on the stucture that might cause it. One might pull 5 or 6 G’s in the break if one wanted to. One could also do a nice roll with very little increas in positive G applied. One is aerobatic, the other is not. What have the Australians done?
By: Joe Petroni - 23rd March 2007 at 21:38
I think the CAA are amazing. They have managed to find a cause and a solution to the Australia crash even before the australian authorities have finished the investigation. Not a knee-jerk reaction by lawyers at all eh!:confused:
Would you want to do aeros in a JP knowing that it could lead to a structural failure?
By: Easy Tiger - 23rd March 2007 at 18:23
I think the CAA are amazing. They have managed to find a cause and a solution to the Australia crash even before the australian authorities have finished the investigation. Not a knee-jerk reaction by lawyers at all eh!:confused:
By: 1958biggles - 23rd March 2007 at 15:15
That would be why I spotted Eddie Todds MK4 up for sale at Doncaster on EBay today then? Whats the point of buying it if you can`t do any of “the fun stuff”
By: Newforest - 23rd March 2007 at 07:26
”Following a recent accident due to wing structural failure, a review of the above CSIs has been conducted and it has been determined that they do not necessarily find cracking if it takes place from the inner surface of the lug where any crack may be obscured by the bush.
Repeated removal of the bush is not advisable as it may introduce damage to the lug bore.”
This would presumably follow from the investigation of the fatal crash in Australia.
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March 23, 2007 at 12:31 am