We're looking for someone with STEC 60-2 in an A36 or B36 in northern Nevada or California. We'd like to borrow your pitch computer for an hour (and buy you lunch at your airport ;-)) For the reason, read on.
We have an STEC 60-2 in a 1984 A36. Like other posters, we have a problem with pitch oscillations (porpoising) but with a twist: ours occurs only above 13000', with a slight dependence on CG. Below 13000' it never occurs and above 13000' with 4 or more passengers, it always occurs with either altitude hold mode or vertical speed mode. We've talked at length with STEC and had 2 STEC avionics shops working on this. Here's what we've tried so far:
1) Static system. The problem still exists after a static system check and with the static line unplugged from the transducer.
2) All cable tensions have been checked.
3) The startup voltage on the pitch servo has been checked.
4) The transducer was tapped lightly with a screw driver to check for noise (STEC's suggestion) and there were no pitch changes induced.
5) The pitch computer has been bench checked twice by 2 different shops. STEC would be happy to check it again (and make adjustments if necessary) for $648. We would be OK with that if we were sure that is where the problem is but we're not.
Which brings us to the idea of swapping with a known good computer. Can you help?