Tonight I installed the WAAS GPS antenna. I’m placing the one behind the GA-35 GPS antenna, and offset to the right, just over 12 inches apart.
The process was the same as the other GPS antenna, although this one is slightly larger and has two 5/8 size holes for the connectors vs just one on the GA-35. Using the back-plate (purchased separately from Stein Air) as a template, I carefully selected the right position making sure it was parallel to the longitudinal axis of the airplane, and clear of the sub structure (j channels, ribs, bulkheads). I used the centerline of rivets to ensure it was parallel, and calculated the required clearance from sub structure, then placed it as far aft as I could. This location gave me just over 12 inches distance edge-to-edge from the two GPS antenna.
I drilled and reamed the holes, and used the step drill to step up the two large holes to 5/8.
Deburring the inside of the holes and then stripping the primer from the underside of the top skin was a challenging step. I had to climb into the baggage compartment then reach back to complete the tasks, which was doable with enough patience.
Dimpling the holes in the skin was also a challenge. I had to use my pop-rivet dimpler, which doesn’t give the best results on a good day, because there’s no other way to access both sides of the skin. I used a step stool to get up off the ground, and then I found I could reach back enough to inset the nail into the hole, and support it while putting the pop riveter into position. it was fiddly, but not hard.
I made quick work of the necessary countersinks, installed the nut plates, and then pop riveted the backplate into position.
I used some silicone and the rubber gasket to install the antenna.
