A page about the control run for the stabilators
At the time of writing (Jan 2002) a thread is in progress concerning play developing in the stabilator control run. Ferg Kyle has drawn a very useful sketch of the components concerned which makes it easier to follow the thread.
To quote Ferg,
There was an earlier thread about TP 5 and TP 6, and now we have a revisit in the Tailplanes line. I got so's I couldn't follow the text of some because of mental confusion, so went back to the tail and re-acquainted myself with it. Thank God, I seem to have put everything in the right place!
However, if it hasn't changed, then perhaps the accompanying sketch might be of use to some. I think I have it all OK. A description might go like:
(1) There are 6 pins - 4 inside the fuselage & 1 in each stab (not shown)
(2) TP6 is buried in the stab, TP5 is in the stab inner face.
(3) TP13 is 4 cups in the stab to mate with the TP12 Drive Plate pins;
(4) TP12s go over the TP4 tube, inside TP11 bushings & pinned under TP10 Plastic Sleeves;
(5) TP10s keep the tube spaced centrally between the TP11 bushings which are bonded to the fuselage sides;
(6) TP9 is driven by the Pitch Control Rod - which twists the TP4 through the 2 inner Clevis pins - which twists the TP12 Drive Plate through the 2 outer Clevis pins - which twists the Stabilator through the TP13 sockets, around the TP6 outer & TP5 inner bearings.
I'm sure someone could do a better job of description than I, but it would have helped me if this had been in the manual. It might also help in the latest thread
Ferg (VE3LVO@rac.ca)
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Bob Harrison has devised a mod to counter the development of play in service between TP12 and TP4 as a result of enlargement of the cotter pin holes. Bob has now received PFA approval for this mod for general use.. Narrative from Bob is below, followed by 'during' and 'after' pictures of the mod.
Regretfully it will not be retro-fittable other than by dismantling the existing set up because the TP10 Nylon bushes need to be shortened from the inboard ends to within 1/32nd " of their locking pin hole diameter. This exposes more of the offending TP12 bush area on which the clamps can address.( there only being about 1/8th " available as standard)
In the event of wear of the TP12 bush holes becoming apparent, providing the nylon bushes have already been shortened (there is no reason why they shouldn't be, since their length is only critical between the pin and the outboard end where they act to stop end float of the torque tube TP4) the clamps can be retro-fitted with one hand through the minimum 5" diameter maintenance hole, without further dismantling of the assembly.
No one can explain why some aircraft are suffering the problem and others aren't. We are confident that the type of wear occurring in the TP12's will be prevented by these clamps, but we of course are unable to predict whether the wear will now start appearing somewhere else, but since the principle of the clamps is to stop all relative movement between the TP12's /TP4/ TP9 then wear from this source will be impossible.
In the case of G-PTAG it would have been ideal to apply the clamps leaving the pins as per their original size to prove that the clamps are eliminating the movement , but I took the opportunity whilst it was all on the bench to ensure that the pins were replaced with 5/16th" so I guess it will be 100 hours down the line before we can check there is NO differential movement between the tail plane trailing edges. However the theory is "no relative movement no wear" plus the added benefit of support to the Torque Tube in bending mode..
The Europa factory are working on increasing the pin size to 3/8" but the TP 12 bush area is still only 1/16th" thick material for wear factors and begging the question of bending stress limitation on the Tube (although they will have proved its integrity prior to appication of the increased size holes) so who's to say that there will or not eventually be wear, and indeed how many hours down the line ?
The easy way to apply our enhancement is prior to putting the
fuselage top
on.
***************************
November 2007 : (following the
appearance of several factory Mods and PFA and CAA bulletins, after an
accident)
Bob Harrison notes :-
"Application of the
Mod No. 10623 ,which is a PFA approved Standard Mod optionally applicable to all
Europas,
exempts owners submitting to 10 hourly inspections and also exempts
them from the necessity to use loctite between the TP5 drive plate bushes and
the torque tube TP4."
Now for the painful bit ..... the cost of the clamps will be advised on
application to Bob, who can be contacted on ptag.dev@tiscali.co.uk.
Bob
Harrison
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(712x1072 pixels, 97KB)
Two pictures are also presented of the mod as installed by a customer, thanks to Gerry.
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(716x1475 pixels, 46KB)
Problems with or comments on these pages please to John Cliff (europa@crix.org.uk) 30/11/07