Found out a single loose ground wire can mess up a whole autopilot system

I was chasing a weird heading drift on a Cessna 172 last week. Pulled the avionics bay apart and found a ground lug that looked fine but was barely snug. Tightened it up and the whole system came back to life. Never would have guessed something that simple could cause such a headache. Made me wonder how many of us actually check ground connections first before diving into the big troubleshooting. Anyone else run into a little thing like that causing big problems?

3 comments

3 Comments

paul_taylor211mo ago

Hard disagree on this one. Ground wires are usually near the bottom of my list unless there's something obvious like corrosion or a loose connection visible. Most heading drift I've seen comes from a bad heading bug calibration or a slipping directional gyro, not a ground lug.

joel_jones29d ago

Had a plane come in last month with a heading drift that drove the owner crazy. Checked the heading bug calibration three times, cleaned the gyro slip ring, everything looked good on paper. Turned out to be a corroded ground strap behind the panel that had about half the strands broken off inside the insulation. Replaced it, drift was gone completely. Grounds are one of those things where you don't think about them until they bite you. Definitely worth a quick resistance check before you start pulling the gyro out.

nancyj1129d ago

Yeah, Joel nailed it with that corrosion finding. @paul_taylor21, you make a fair point about priorities, but I've had two cases this year where a ground issue was the whole problem after everything else tested fine. It's one of those things that seems too simple to check, but sometimes the simplest fix saves you from chasing ghosts for three days.