Caught a bad ground loop at a regional airport last Tuesday

Was doing a routine pitot static check on a Cessna 172 at KMDH. Hooked up my test set and got weird readings that made no sense. Spent an hour chasing wires before an old timer walked over. He pointed at the static port ground strap - loose as could be. Fixed it in 2 minutes with a fresh lock washer. Now I check every ground strap first before touching anything else. Anyone else run into phantom issues that were just bad grounds?

3 comments

3 Comments

keith_bennett1mo ago

Kinda feels like people treat loose grounds like they're the root of all evil in aviation. I've heard this same story a dozen times and honestly most of my electrical gremlins turned out to be bad connectors or corrosion, not the ground strap itself. Maybe I've just been lucky, but I think the old timer wisdom gets a little overhyped sometimes.

the_thomas1mo ago

Did the old timer say what kind of issues he's seen from loose ground straps before, like weird avionics glitches or just bad test readings?

taraross1mo ago

Loose ground straps can cause both weird avionics glitches AND bad test readings honestly. The old timer told me he once had a plane where the transponder would randomly stop working mid flight and it traced right back to a loose engine ground strap. Another time a customer kept getting intermittent altimeter errors that drove everyone nuts for weeks before they found the main battery ground was barely hanging on. But avionics glitches are way more common than just bad test readings, that's where you'll notice it first.