Re. the recent traffic on strengthening the TP6 bond, it seems possible that
we may have been trying to cure the result and not the cause. I have now had
to do them twice in spite of considerable roughening, inserted screws and
dimpling. More than one of us has now found this to be associated with
slightly slack drive plates (TP12). These are held to the tailplane tube by
pins. If there is any slackness at all here, then the load is immediately
taken by the pip-pins and through the TP6's into the bond which is not
designed for such loads.
I find that the rear of one tailplane can be lifted relative to the other by
4mm and another builder is finding 10 mm ! Neither of us believe this to have
been present at build time. This points to development of a significant
enlargement of the hole(s) carrying the pins which secure the TP12's.
Effecting a cure here inside the fuselage is difficult. Either the existing
holes need re-boring and larger pins fitted, or extra pins/rivets are needed
to attach the TP12's.
This is significantly major for us to await a factory response. In the
meantime I would suggest everyone check for relative movement of the two
TP12's on the tailplane tube. Both of these aircraft have done under 100 hrs.
Graham C. G-EMIN
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