Tuesday, September 29, 2015

Baggage Door - EAA Tech Counselor Visit #3

One step closer to finishing the baggage door! Tonight I fabricated and installed a stiffening plate across the baggage door frame where I had cut it to fit the latch. I'm pleased to say it added the exact stiffness I was hoping it would, and now the only thing left to do is find and install a mini strut to hold the door open and prevent it from opening too far.

The stiffening plate connecting the two halves of the baggage door

As for the strut, I believe I've found the correct part for that from McMaster-Carr, P/N 9417K6, a "Miniature Gas Spring" with travel from 5.55" - 9.05" and 20lb force (edit- see later post here, recommend 5lb force instead), combined with P/N 9417K92, the accompanying mount bracket (edit- this bracket is too big and bulky, just make your own out of aluminum angle). The parts are on their way, and I'm hoping they work out nicely. After that is installed, we're just a few blind rivets away from calling the baggage door 100% complete!

In other news, our EAA Tech Counselor came by tonight for a visit to see the project. This is technically his third time here in the shop, but the first time was before we even set our first rivet on the empennage kit, just to look over our shop and tools, and to make sure we were on the right track. The second visit was after we had completed the elevators but hadn't yet started on the tailcone. Unfortunately, during those previous visits we never completed any official EAA paperwork to document the inspections (other than logging it ourselves). No big deal but in hindsight it would have been nice to have done it just to cross t's and dot i's. This time, though, we got our yellow slip:

EAA Tech Counselor Notes

He did an extremely thorough job inspecting the wings and fuselage, and I'm happy to say that overall he had some very positive feedback for us. He even noted "excellent workmanship overall" in the comments.... wahoo! Talk about how to brighten someone's day. It felt incredibly rewarding to have an expert in E-AB aircraft (and an RV-6 builder/owner himself) look over our work and give it the thumbs-up. The only thing he noticed was on the aileron torque tubes, the nuts holding the tubes to the bearings didn't have enough thread showing. The FAA rule is that there must be at least 2 threads showing beyond the nut, and on our wings that didn't work out to be the case:

The aileron torque tubes with AN365 locknut and washer, and only ~1 thread sticking out the top

I was already aware of the "2-thread" rule, but admittedly I guess I thought it was more of a guideline and not a hard-fast rule. Also, I thought I had the hardware installed per the plans, so "it must be right." Plus, the way the whole tube is in there, there's no way it's coming out even if the nut were to fall of entirely somehow. So at first it seemed like kind of a trivial finding, but since it's an FAA rule and will surely be looked at by the DAR when they come to inspect the plane for airworthiness, this could end up costing us a fair amount of time (likely several weeks) if they ding us for it and make us fix it, then we'd have to perform the fix and reschedule a time for another inspection. Way better to remedy this now!

So how did this happen in the first place? Well, we got out the plans for the wing and turned to Section 23 (aileron actuation) and reviewed the hardware callouts. Guess what? We goofed. They call for an AN364 (which is a low-profile version of the more common AN365) locknut to be installed in this location... oops!

The hardware callouts in the plans, Section 23-7, Figure 1

Simple oversight on my part in the callouts. Definitely a good catch, and lesson learned! I'll have to dig up the correct hardware (couldn't find any AN364 nuts in my hardware bins) and swap them into place, should be a very straightforward fix.

Other than that one finding, everything else went very well during the inspection! We then spent a long time discussing all kinds of things from avionics to flight characteristics, and all the different aircraft he's seen over the years. I can't possibly stress how thankful I am that a program like EAA's Tech Counselor program exists, and even more so for the individual counselors who volunteer their time to help others like us get through their build in a correct and safe manner. Thanks Tom! :-)