"Bob Chilcoat" wrote snip

Another possible failure mode is for the screw to strip so badly that some
or all antiservo function of the tab is lost. This could result in extreme
difficulty in controlling pitch. Anyone have thoughts on how bad this might
be? I have trouble imagining the screw stripping rapidly to the point that
the screw could slide freely up and down inside the drum, but it might be
possible. How can we find out how bad this would be? Is the antiservo
function essential for flight control, or is it just to improve the "feel"
of the controls?

An final concern is that with the extreme looseness we have now, the flutter
margins might be significantly compromised. Stabilator flutter could
certainly result in catastrophic failure modes! This is another potential
ramification of flying with it in the current state. Any thoughts on how to
research this possibility?

Bob, I'm kinda worried about this. On my snub-nose Aztec the
stabilator has a similar "antiservo" surface that "drives" the entire
stabilator. By pulling on the yoke you are first moving that tab
which in result "flys" the entire tail to a new pitch command
position. Loss of control of that tab suface (i.e. trim jackscrew
unexpectedly strips) at least on my bird, will not just loose trim,
but could, if it shears past the limit, loose all longitudinal pitch
control. I had a seperate A&P look at it and he was of the opinion
that it wouldn't shear past the limit even if all the threads stripped
off. To this day I'm not so sure. Let's face it. This is test pilot
****. My airplane has almost 5000 airframe hours on it and was used
in bush ops for a long time (gritty environment.) Seperately, I had
bad flutter in this airplane in 90 degree banks with a neighbor on
board. (This airplane had tail damage in the 60's before I bought it
and rearmost bracket had been repaired.) We landed and discovered
during the next annual that the Jesus bolt that connects the pitch
control rod to the stabilator tab bracket had worn an egg-shaped hole
in it, and that the hole's edge on the control rod mounting bracket
was paper thin. A little more flutter and we would have lost all
pitch control (i.e. kiss your ass goodbye.) The flutter occured at
about 140mph IIRC, shook the yoke and sounded like somebody shaking a
metal garage door at the bottom. IMHO, you shouldn't screw around
with this (pardon the pun.) As the poster said above, if it's close
to max play; ground the thing.

pacplyer

p.s. did I say 90 degree banks? I meant 60 degree banks. Pushed the
wrong button again. I hate it when that happens. ;-)