<<..Any advice is welcome. .>>
OK, I'll bite!
During a monowheel collapse, the weight of the aircraft (less tailwheel and
outrigger loads) is transferred from the monowheel in to the top of the
'tunnel'. Thereafter, the stress-path from the tunnel is mostly both
forwards and aftwards. In the aft direction the tunnel distributes loads in
to the seatback bulkhead then further in to the fuselage skin. This means
that the area that has cracked (being at along this stress-path is taking
abnormal loads and this is a possible cause of the cracking, as you have
surmised, compounded by the holes that have been cut at that point.
Assuming there is no evidence of any other overstress in that area, the
repair needs to put back the strength lost. This means replication of the
original strength of composite in that location, which can be determined by
counting the number of plies present. Allow a minimum 1/2 inch per ply
overlap on to the surrounding unaffected area (presuming a bond shear
strength of 500psi and cloth strength of 250lbs/in) with staggered edges. If
the holes must be recut, then double the reinforcement and cut the holes as
ellipses (at a length:width ratio of 1.414:1, if you want to be pedantic!).
Too much or overdesigned reinforcement may make the area too stiff and
introduce other issues, and makes the aircraft heavy too!
Your respective airworthiness and/or design authority will be the final
arbiter of any repair, which might be along the lines of the above.
Duncan McF.
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of ploucandco
Sent: 25 August 2012 18:26
Subject: Europa-List: Re: Cracks on the cockpit module near to the seat
belts
--> <jacques@platisource.com>
Hi all, here is a drawing of the cockpit module that shows with red
rectangles the place where the pictures have been taken and so the location
of the cracks. Will 5 BID at both side of the existing panel and on the
cracks location be enough to repair and prevent reoccurence?
Thanks, Jacques
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http://forums.matronics.com/viewtopic.php?p=381795#381795
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