>This is like treating the symptom and not the illness. The play comes
---From
the TP10 fixing on the torque tube. If the pip pin fixes well, the play
is
tranferred on the glue of the TP6 in the foam! If there is any flutter
then
you can imagine how long it will take before the TP6 comes untie.<
I agree that the problem starts with the fixing of the TP10's. However
the design of the pip pin recess is still important. A small amount of
relative movement between the tailplanes (caused by the less than
perfect fixing of the TP10's) is not in itself dangerous. Neither is
disbonding of the TP6's by itself. What is dangerous is if the
tailplanes move outwards allowing them to disconnect from the TP10 pins.
If the TP6 becomes disbonded (by for instance twisting loads) it is
possible in some cases for the tailplane to move outwards sufficiently
for the tailplane to become disconnected from the TP10 pins. The size
and shape of the recess is important in this respect. A recess sidewall
which is close to the pip pin head on the inboard side can prevent
outward movement of the tailplane whilst the pip pin is in place even if
the TP6 is disbonded.
Although flutter has been mentioned (and can be a very dangerous
condition), a possible cause of this inflight loss of control is a
tailplane moving outwards enough to become detached from its TP10 pins.
Regardless of the TP10 fixing it is important that this is not allowed
to happen.
I know that the PFA is looking at a modification to the pip pin recess
so we will just have to wait to see what they come up with.
Nigel Charles
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