Brief Description: Attaching the Root Ribs and Snap Bushings
The root ribs should be a comfortable attachment. They are installed using AN426AD3-3.5 flush rivets which can be squeezed. So I am struggling to explain why I had to drill one of them out twice. Regardless, there was no damage to the hole and the final rivet is very good.
These rivets need to be nice and flush as there is no replacement of them without removing the control horn which would be very hard to do. The photos give before and after images and demonstrate the simplicity of the task. The only complication is the overhand of the root rib itself. I ended up using the flush set on my Pneumatic squeezer with a 4 inch low profile yoke to minimise any interference with the overhanging root rib.
The most cosmetic solution would have been to put the manufactured head on the control horn and the shop head on the inside of the rib, however, I chose to put the manufactured head on the weaker component ie the root rib and spar and the shop head on the steel control horn. When there is no net difference, I go for cosmetics, but here, I went for strength. The plans do not provide any specific guidance.
I have installed the snap busings with RTV. I find the oreintation of these bushings interesting as they protrude quite a long way from the spar. I am guessing that this approach has been taken to ensure that the fitting that passes through the bush is controled when near to the moving surface of the leading edge of the elevator.
