My partner and I are trying to troubleshoot a problem with our STEC60.
The unit was working fine before the plane went into our local shop for a CGR30P install.
Right after the install, I took the plane on a trip. On the return home, I was at 8000' with alt hold engaged and the trim started rolling nose-up by itself. I recognized it, turned off ALT mode on the STEC, retrimmed manually, checked all the breakers, and re-engaged. It was fine after that.
The next day, I flew the plane from home base to RYY for its annual. Alt hold worked fine there.
When my partner picked it up, on the home leg he complained of pitch excursions but found that the PSS mode selector was in "test".
On his next flight, which was yesterday, he complained that when engaged, the STEC pitched nose-down uncommanded. He disabled the system and continued the flight normally. After landing, he checked the wiring on the back of the unit (he's an electrical engineer, so he's always checking some wiring somewhere) and said the connector was not plugged firmly into the detents.
I haven't had a chance to ground-check the unit to see whether it trims uncommanded on the ground but that would certainly be interesting to know.
Based on what I know about the PSS, it doesn't seem like a loose connector would necessarily cause the symptoms we saw, and I'm inclined not to suspect either the servo (it obviously rolls trim in or out, just not when we want it to) or the transducer (I'd expect it to be biased in one direction or the other, but not both).
Any suggestions for what else to check?
The unit was working fine before the plane went into our local shop for a CGR30P install.
Right after the install, I took the plane on a trip. On the return home, I was at 8000' with alt hold engaged and the trim started rolling nose-up by itself. I recognized it, turned off ALT mode on the STEC, retrimmed manually, checked all the breakers, and re-engaged. It was fine after that.
The next day, I flew the plane from home base to RYY for its annual. Alt hold worked fine there.
When my partner picked it up, on the home leg he complained of pitch excursions but found that the PSS mode selector was in "test".
On his next flight, which was yesterday, he complained that when engaged, the STEC pitched nose-down uncommanded. He disabled the system and continued the flight normally. After landing, he checked the wiring on the back of the unit (he's an electrical engineer, so he's always checking some wiring somewhere) and said the connector was not plugged firmly into the detents.
I haven't had a chance to ground-check the unit to see whether it trims uncommanded on the ground but that would certainly be interesting to know.
Based on what I know about the PSS, it doesn't seem like a loose connector would necessarily cause the symptoms we saw, and I'm inclined not to suspect either the servo (it obviously rolls trim in or out, just not when we want it to) or the transducer (I'd expect it to be biased in one direction or the other, but not both).
Any suggestions for what else to check?
