(W9MV) wrote in message ...

The Stec is very sensitive to static port performance. On
some aircraft, like C 182 models, you need to add some
separate static ports to make it work.

I have a hunch that you have a little water in your static
system. If the changes in air pressure have to drive a water
plug, it will make the autopilot nuts.

Bill Hale BPPP instructor


I have an S-tec 55 in a 1999 Piper Archer III.

Last weekend I was in moderate rain in a climb out of 2000 feet (900 AGL)
heading for 6000 feet when all of the sudden the nose pitched down.

I pushed the two drains located in the cockpit when the event first occured and
it did not solve the problem.

I disconnected the autopilot and handflew it. When it was safe to do so, I
engaged the autopilot again, and again, it would either pitch up or down.

Later in the flight when the rain had stopped, it worked as usual.

Any ideas?

Mark