david920•2d agoProlific Poster

I finally figured out why that old Garmin GNS 430 kept dropping GPS signal on a King Air last Tuesday.

Spent half a day chasing it. The coax from the antenna to the unit looked fine, connectors were tight. I was about to condemn the box itself. On a whim, I pulled the antenna base off the skin and found the ground plane was completely corroded under the sealant. Cleaned it up with a scotch-brite pad and some contact cleaner, resealed it with PRC. Signal locked right in and held. Has anyone else run into that on those older flush-mount antennas? I feel like it's a sneaky one.

3 comments

3 Comments

dylanrodriguez2d ago

Heard a mechanic call that the "hidden ground" problem, it's more common than you'd think.

blair9902d ago

Seen it before too. That hidden corrosion is a real pain.

kelly_rivera2d ago

Yeah, that "corroded under the sealant" thing is a classic. I've seen it a bunch on older GA planes, especially where the sealant fails and lets moisture sit right on the metal. Had a Cessna 182 with the same exact problem, kept getting random signal loss. Cleaning up that ground plane with a scotch-brite pad and a good dielectric grease before the new sealant usually fixes it for good.