Roger,
I think you will find that the apparent wear on your TP12 is in fact
where it was ground by the manufacturers to true up the original tube. I
have seen a new, complete assembly that has never been fitted with
apparent wear marks, but on closer examination it cam be seen to be a
ridge left after grinding. The TP12's on my own a/c were never ground
very well, with the result when I grasp the torque tube and rock it, I
have a slight movement up and down, but nothing in the horizontal plane.
Jim
----- Original Message -----
From: ROGER MILLS
To: europa-list@matronics.com
Sent: Thursday, July 19, 2007 10:15 AM
Subject: Re: Europa-List: TP6 Bonding
Like Bryan and Bob Harrison, I too found an excellent bond between rib
and TP6 and agree with Bryan's point about feedback - here's some more
which might help others:
1. I agree with the guidance in mod 73 not to use power tools - I used
hand tools and was glad I did, the foam is easily damaged.
2. Having had (I thought) almost 3/8" play at the tailplane trailing
edge, I intended to do mod 62 at the same time as mod 73. Having
extracted the torque tube from the fuselage, I find that the pins are
reasonably tight and there is significantly less TP12 to TP4 play than
first thought. Investigation shows that there is some wear between the
TP11s and TP12s which contributes to the play observed on the aircraft.
After 440 hours, TP11 appears to be hardly worn but there is a visible
track worn into TP12 and some eccentricity (a bit like its owner?). I
have seen the same wear pattern on other online photographs of TP12s -
so I'm not alone! Since Mod 62 might not lead to a significant
improvement, I'm tending towards not doing it until there is more wear -
to avoid risking ending up with the a similar degree of play and nowhere
else to go (apart from Bob's clamp mod maybe). Presumably TP11 to TP12
wear is not as critical as TP12 to TP4 - assuming good mass balance?
Which leads to the next point:
3. While the tailplanes and torque tube were out of the aircraft I
decided to do a check of the mass balance and was surprised to find the
assembly 78g too heavy at the weight end. I genuinely thought I had
achieved a good re-balance in situ after mod 70 but the friction in the
control system was enough to mask the imbalance. How many more Europas
are like this and might it have contributed to the accident?
Since correct mass balance is so critical and removal of the torque
tube (albeit a pain) takes less than a day's work, it might be worth
doing this at the same time as mod 73 - giving the advantage of peace of
mind and also being able to use your own torque tube for a better layup
than wrapping tape around plastic pipe as some have suggested?
Hope this helps!
Roger Mills
Roger Mills
07921140616
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