Caught a fellow tech wiring the wrong ground reference on a G1000 yesterday

He had the shield tied to the airframe at both ends instead of just one, which created a loop and messed up the COM radio. Has anyone else seen this mistake causing intermittent squelch issues?

2 comments

2 Comments

olivia_hernandez12d ago

Saw that exact thing on a King Air install last year. The shield was bonded at both ends and it caused the COM to drop out every time the strobes flashed. Took me a full afternoon to trace it because the squelch was fine on the ground but acted up in the air. Finally clipped the shield at one end and the radio worked perfect after that. Aviation wiring manuals are dead clear about this, but people still skip it.

the_blair12d ago

Wow, that's a real head scratcher. But I gotta ask - did you check if the shield was bonded to the airframe or to a separate ground plane? Because I've seen guys bond it to a standoff that's technically bonded to the airframe but has a different potential than the main ground bus, and it makes things way worse. I swear some installers just see a ground screw and think "that'll work" without thinking about the return path for those strobe pulses. Those high current pulses love finding weak spots in bonding. What was the actual resistance reading on that shield bond before you clipped it? I'm betting it was higher than you'd think.

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