I finally found the smoking gun on intermittent NAV faults, it was the antenna coax

Been chasing a drop in NAV signal on a King KX165 for 3 weeks. Replaced the unit, checked the tray, reseated connectors, still dropped out every 40 minutes or so. Found a tiny water trail inside the RG-58 coax at the antenna base, just a pinprick. Cut it back 2 inches, re-terminated, done. 12 flights since, no issue. Who else has had coax corrosion hide that well?

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1 Comment

masonm7012d ago

Shit, that's a sneaky one. I remember reading an old A&P forum thread years back where a guy had the exact same thing on a Cessna 172, water got in through a cracked antenna O-ring and just sat there. It's wild how a tiny bit of moisture can travel down the braid and cause intermittent shit that drives you nuts. Most guys I know would have swapped the whole coax run by then, so props for actually finding the pinprick. It's always the stuff you can't see that bites you in the ass.