S-TEC 60-2 requires re-trim after altitude hold?

On Mon, 1 Mar 2004 10:07:19 -0500, Peter R.
wrote:

Speaking of the S-Tec 60-2, I am transitioning to a Bonanza V35B that is
equipped with this AP. The previous owner demonstrated an idiosyncrasy
with the AP that I would like to correct, if possible.

I don't think you are going to find any thing wrong with the AP.
OTOH my experience is limited to only a couple of planes and mine has
an S-Tec 50 with altitude hold.

Using the AP to hold VSI, the aircraft is in a climb. Upon reaching the
assigned altitude, I push the ALT button on the AP. The aircraft, since it
overshot the altitude by 100 feet or so, descends and levels off at the
altitude where I engaged the ALT hold, then begins a speed increase to
cruise speed.

Is the speed exactly the same as it was prior to the climb, or is the
power setting the same?

If you have climbed and the bo is going faster it will require the
trim be reset.


Now for the idiosyncrasy: The AP is engaged and the aircraft is holding
perfectly at the desired altitude. However, if I disengage the AP, the
aircraft immediately begins a climb, suggesting that there is a slight
nose-up trim situation that was being held back by the AP.

To overcome this, the previous owner suggested that after level-off,
disengage the AP, manually re-trim, then re-engage the AP.

The Bo is very sensitive to trim and speed. slight differences are
going to require retrimming. The AP will correct the situation, but
when disconnected the trim will go back to its manual setting
resulting in a climb or descent. If very far out of trim the change
can be rather abrupt.


How can the S-TEC AP be adjusted to hold the altitude after a climb without
the nose-up trim problem? It seems to me that, over time, this problem
could result in premature wear and tear of the AP control servos, no?

As the AP is continually adjusting the trim, it's unlikely it would
add any wear due to the out-of-trim situation.
Get into some turbulence and that sucker can change so fast it'll do a
better job of holding altitude that I can. OTOH that's when I turn it
off to reduce stresses.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com