2 Oct 2023

Assembled rear seat backrests. This proved trickier than I had anticipated, mainly because the rear skins for the seats are not pre-drilled to accommodate the M4 rivnuts required for the various locking mechanisms. It also requires countersinking for the stainless steel rivets to hold a nutplate in position - this is not called out in the KAI, so it meant countersinking after I had already applied primer (ditto for the hole enlargement to suit the rivnuts).

The fuselage KAI is proving to be far less detailed and informative than the empennage and wing documentation, with some critical information missing and / or errors.. Two of the holes pass through the backrest side channels, so the rivnuts need to be installed when the rear skin is attached to the rest of the structure. I aligned the top holes when drilling for the rivnuts by upsizing the bottom holes first and then using the rivnuts loosely in the holes, with the buttonhead screws through the bracket and tightened by hand to provide a firm drilling template. Check the direction of the brackets! The rear skin needs to be removed after upsizing the holes to 6mm in order to debur them, then refitted whilst keeping the front skin only cleco'd in place so that it can be removed to check that the rivnuts have correctly seated.

I installed the rivnuts in the wrong position on the left seat since I was following the orientation for the spacer plates as per the KAI rather than the split seat bracket 1 - the spacers seem to be reversed in the KAI diagram, and to compound the issue there are also only 6 holes illustrated for the split seat bracket 2 whereas the spacers require 7 holes, which makes it a bit confusing to confirm the orientation. I have a plan to fix this by reversing bracket 1 and trimming the side to suit the seat profile. I think the final result will actually be more practical than the factory setup because it will be easier to access the end of the seat latch to open it.