The weirdest before-and-after on a King Air's transponder I've ever seen

Last month, this thing was giving us a perfect, solid reply on the bench test, but after we reinstalled it in the bird, the signal strength dropped by over 30% for no clear reason. We finally traced it to a single, slightly-corroded BNC connector in the antenna feed line that must have gotten jostled during the reinstall. Has anyone else had a connector pass a bench check but fail the moment you put real flight loads on it?

3 comments

3 Comments

miles9461mo ago

A bench test is a static check, it doesn't put any physical stress on the line. Vibration and flexing in flight can open up a tiny crack in the solder or a corroded pin that was just barely making contact on the ground. It's classic. Seen it with D-sub connectors on avionics racks too, they'll pass power-up but drop data when the airframe shakes.

olivia_allen1mo ago

Honestly, that makes total sense. I read a case study once about a helicopter that kept having nav system resets. They bench tested everything for weeks and found nothing. Turned out to be a cracked solder joint on a board connector that only lost contact during certain vibrations. It's crazy how something you can't even see sitting still can cause a huge problem when things start moving.

kai_butler8324d ago

Funny how that applies everywhere, right? I swear my car has a phantom rattle that only happens when I’m on a specific bumpy road, but as soon as I pull into the mechanic’s lot, it’s dead silent.