In message , "W.J. (Bill) Dean
(U.K.)." writes
If you wish to know what can go wrong with a wooden Schleicher glider see
http://www.tux.org/~milgram/k8.html which I have copied from a posting to
another thread.
Yes, scary.
I remember seeing a K8 over 20 years ago being re-covered, there was a lot
of structure aft of the spar with glue failure.
From the completely hearsay mutterings of a few inspectors I know, the
current mandatory inspections haven't thrown up much but I think that a
lot of the potential bad ones needing rebuilds have been culled out in
the last few years. However it does mean that if you see one that has
been "away" for a long time then it needs a very thorough inspection and
questioning the quality of the structure.
I was told that the main 'D' box was built in the factory using Aerodux or
similar, but the aft structure ribs etc. were built by out workers in their
homes, and used a single part glue which was not waterproof; it is this
"pink" glue which fails.
For the earlier ones, yes. I think most of the Ka series gliders were
built in this way. Perhaps not the later 13s that Jubi built but almost
certainly 6s, 7s, 8s, and earlier 13s. Somewhere in all of this they
dropped the "pink glue" and also an earlier "white" glue and went
totally over to Aerodux or something similar.
I have since then heard of many wooden 'K' series needing major re-building
of the structure aft of the spar. One friend sold his K6E trailer with the
glider free inside it, a professional rebuild would have been uneconomic and
he did not have the skills to do it himself; it has been bought by someone
looking for a project. Another club K6CR was condemned as needing a major
rebuild, again it has been bought as a project.
Schleicher originally covered all these gliders with cotton, I think there
is much sense in the suggestion that they should all be re-covered every 10
years.
I think I agree with this and I don't think that it is limited to
Schleicher. The mandatory inspections called for holes in the D box and
in the wing fabric around the airbrake area followed by a good look
round with a boroscope. Personally I think that this is a good idea in
most wood gliders based on looking inside a number of other
manufacturer's wings.
I think that what we have to remember that all of these aircraft are
quite old, say 35 plus years, and have had many many launches and hours
flown. As a result they have been stress cycled more often that we can
ever imagine. Add to that the use of old technology glues and often
kept in damp/humid conditions at some time in their life and you have to
wonder. Having said that most of them are perfectly serviceable and
given care, regular inspection, and replacement of faulty components as
they occur should keep going for a long time. Just don't think of them
as indestructible.
Robin
The K7 crash on 26th May 2004 which killed two people and which led to the
BGA Mandatory Inspection is being investigated by the AAIB, they have not
yet reported. However the preliminary BGA report includes the statement
that "The aircraft was seen to lose the major part of the starboard wing
shortly after completing a winch launch and whilst carrying out what
appeared to be clearing turns".
W.J. (Bill) Dean (U.K.).
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"W.J. (Bill) Dean (U.K.)." wrote in message
...
There has been discussion about the life of wooden gliders.
Anyone owning or thinking of buying a Schleicher wooden glider should look
at the inspections required by the British Gliding Association.
This is British Gliding Association mandatory aircraft inspection number
042/07/2004 issue 2, dated 12 August 2004, which may be found at
http://www.gliding.co.uk/bgainfo/tec...2-07-2004-issu
e-2.pdf .
W.J. (Bill) Dean (U.K.).
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--
Robin Birch