Mailing List lml@lancaironline.net Message #11281
From: Jeffery Peterson <jbp@fire.phys.cmu.edu>
Subject: 360 pitch trim.
Date: Wed, 17 Oct 2001 08:29:23 -0400 (EDT)
To: Lancair <lancair.list@olsusa.com>
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> I have too much sensitivity in my pitch trim.  Way too much.  I thought I
...
> I am thinking the tab is too big.  What
> thinks the rest of the list???
>
> Thanks,
>
> Matt
I am about to cut out my trim tab so I am very interested in this issue.

At first you might think "more is better" when it come to trim tabs.
But a too-large trim tab can be dangerous.

In previous discusions on LNC2 trim I remember that one pilot was
worried about run away electric trim.  One open wire would put you in
the failure mode in which you could trim one way then not be able to
remove that trim. A confused pilot trying to figure out the failure might
repeatedly try each direction, getting himself deeper in trouble every
time.

I recall a commment that dialing in full trim, the stick force
needed to counteract that trim was more than the pilot could muster.
This strikes me as very bad indeed, and if true it would indicate that
the tab, (or its angle limit range) really is too big.

The trim tab size and range should be set so that at the either limit the
stick force need continue flight, then to descend, then flair should be
fairly easy to hold for the time needed to land.  say 1/2 hour.  how much
force is that? 10 lb?

What are the stick forces at full trim?  is the full range needed to trim
for both cruise and landing approach?

-Jeff Peterson
LNC2 80%

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