14 Hantone HillWhile there may be doubt whether the shallow lip on the
inside of TP6 will be adequate as a tailplane retention, it is worth
reading EA2004's reasoning behind Mod 73 carefully: Retention of the
tailplane by TP6 (and the pip pin securing TP6 to the torque tube) AND a
secondary retention by the pip pin and its surrounding composite
structure alone, should the primary retention not hold. The mod is
therefore as much a strengthening of the structure around the pip pin
and a proper transfer of forces acting on the pip pin into the tailplane
skin, as it is a mod for better bonding of TP6 to the tailplane.
This is the reason why the instructions make a point of not removing any
bid/epoxy around the hole on the underside, in the event the pip pin
ball should not open on the underside of the new layup, but instead buy
a longer pip pin. Removing bid/epoxy here would defeat that secondary
retention function of the mod.
As I understand it, this view is also reflected in FSB-006 Issue 3
section 5: Mod 73 need to be done if the upper pip pin recess does not
satisfy the stated requirements. I think, however, that PFA ought to
have required ovalization of the torque tube holes even if Mod 73 may be
omitted if the requirements of Section 5 are complied with -ovalization
should be done in any event, I think.
Regards,
Svein
LN-SKJ
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