A sticky autopilot trim issue on a King Air made me question my own wiring check

We had a plane in the hangar with an intermittent pitch trim runaway. I was sure it was a bad servo motor, so I swapped it out. The problem came back after two flights. I finally traced it to a single pin in a 40-pin D-sub connector that had a tiny bit of green corrosion, something I missed because the visual inspection looked fine. Has anyone else had a gremlin hide in a connector you swore you checked?

3 comments

3 Comments

david73923d ago

Tell me about it, I've stared at a perfect-looking pin for an hour before spotting the problem.

aaron7081mo ago

Yeah, those D-sub pins are sneaky... I've been burned by that before, but it was on a nav light circuit. The thing is, a visual check isn't enough sometimes. You really have to get in there with a pick and feel for that tiny bit of grit or drag on each pin. A quick continuity check with a meter while you wiggle the connector is the only way to be sure.

uma_webb281mo ago

Totally agree with @aaron708 on the wiggle test with a meter. Seen it on old flight control runs where the pins looked perfect but the reading jumped all over with a little pressure. That grit feeling is key, like catching a tiny burr on a pin you'd swear was clean. Makes you check every single one, even on a simple 9-pin.