Congratulations Graham,
Looks like you've figured out the cause for TP6's unbonding.
As a non-mechanical engineer, I had a thought for a crude solution: cut a 1/2
inch long section of 1.5+ inch stainless tube - same as the material for the
TP12's - and split this lengthwise to yield two "C" shaped pieces (remove a
few mills from the end of one so the ends don't butt when placed around the
torque tube). Place these against the inboard end of TP12 where it protrudes
---From the plastic of TP10. Place a stainless hose clamp - a longer version of
those used in the fuel system - over this junction and hard up against TP10
and tighten. Friction between the clamp and the metal of TP12 should lock
them together and friction between the clamped "C" sections and the torque
tube should lock the lot together - sort of a metal to metal clutch in the
"lock up" mode.The resulting force would be a shear along the length of the
clamp where the "C's" butt against TP12.
An improved version of this concept would be machined "C" sections with a bolt
on each side to allow tightening.
And, since the tailplane drive arm uses the same type of pins, one should
expect the same problem there....
There is about a 35 time movement multiplication factor between the radius of
the torque tube and the aft end of the tailplane so only a few mils slop at
the pin results in a half inch travel of the TE. While I don't advocate it,
enlarging the holes in TP6 by just a few mils would allow some slop in the
TP14 pin without forcing a failure in the TP6 bond.
Keep up the good work and pray for a solution from Europa which doesn't
require removing the torque tube.
Regards, John A044
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