Van's RV-9A in Aurora

The Big Picture

The Big Picture
Flying! 8/28/2011

Wednesday, August 5, 2009

For Tuesday, 8/4
2 hrs
Started designing the ELT mounting bracket. Decided to mount it to the J stiffeners in the aft fuselage like the Van's brackets allow, instead of under the baggage floor. My reasoning is:
1. The ELT would fit in under the baggage floor, but there was only about a 1/4" clearance between it and the bottom skin. In an event that intruded into the botttom skin, would the ELT survive?
2. The baggage floor location required a longer antenna run than the stock 6 foot cable would allow. I could get a longer cable, but now I don't have to.
3. AC 43-13 recommends the ELT be in the same assembly as the antenna, to prevent the antenna cable from crossing any joint between subassemblies that might come apart in a crash. I doubt the aft fuselage would break off there, but the new mounting location meets this requirement.
4. Van's thought the stiffener location was acceptable.
5. Mounting it under the floor allows access without having to remove all of the screws on the aft fuselage access panel. But hey, you should be looking back there every one in a while anyway, so those screws need to be removed sometime.

Used .040 sheet for the bracket. Cut it out, drilled the relief holes for the bends, and bent the material to form mounting and reinforcing flanges. A trial fit seems to work perfectly.

Also primed the bottom flanges of all of the ribs for the center section. Only primed the parts that will have metal/metal contact with exterior skins. The interior should stay dry. Also, Sherwin-Williams didn't have the 955 primer I've been using, and I didn't want to use the 988 on all of those ribs.