GSU-25

I have a lot of catching up to do in terms of blogging. I hope to sit down and convert some of my work logs and photos to blog posts over the next couple of days. I will start with this post as a warning. The GSU-25 has a non-symmetric footprint! Yesterday I build a doubler for mounting both of my GSU-25s (primary and backup) in the common spot on the far left hand side of the mid-panel. I test fit the GSU-25s to the doubler and proceeded to rivet the doubler to the mid-panel.



I was intending to install the GSUs to the panel with the d-sub connections closes to the ground however when I went to bolt them in place (after I had everything riveted together the bolt holes did not line up. The holes were at least an 1/8" off. I spent a good 5 minutes trying to figure out how riveting the doubler in place deformed the layout that significantly. However, when I rotated the assembly 180 degrees everything was perfect on both GSUs. A quick glance at the mechanical drawing confirms it. The whole pattern is in fact not symmetric. In thinking about it, that was probably done on purpose such that if the LRU ever needed to be serviced or replaced that it could only be re-installed in the orientation that it was previously installed in.


Because Garmin accepts basically every install orientation (with a software configuration setting), I am going to keep this as is (upside down for me), and move on to the GTR-20 installation.

Wiring Diagram

My wiring diagram is coming along and I am feeling pretty stable on the overall plan now. I am going to go with a 2 battery approach so I can have a master and aux. The ignitions connected to the master_battery_bus and aux_battery_bus. The aux bus will feed the backup power on my avionics while the master bus will feed the main_bus. The aux bus will get it's power through a diode connected to the master bus. I cannot recall what exact AeroElectric diagram this is, but I think it is a hybrid between Z14 and Z19 if I recall correctly.




I have made decent progress on building the "Garmin" and "VPX" eagle library. I still have a bunch of components to add, but I am doing them one at a time as I add the component to my electrical diagram.

Send me an email if you want me to send you the LBR with the Garmin and VPX components.

Door latches

I need to come back here and do the write-up, but here is my page to document my Plane Around 180 kit and AeroSport low profile door handle install.

Rear Accessory Shelves

As I was planning my electrical system I realized that I needed some additional space behind the rear bulkhead for my E-bus, battery bus, and additional contactor. I remember seeing a PDF from TCW regarding the dimensions for a rear shelf, and having worked through a couple of designs, the tray layout from TCW was pretty much what I wanted.

I started the process by cutting the shelfs out of .063 6160 and bending the two edges down for stability. I ended up bending my down rather than up (well I guess I ended up doing exactly what TCW did, but I installed my flipped upside down)




Not that I would recommend you go out and buy a harbor freight brake (because I hate Harbor Freight), I will say that for $40 dollars being able to form a no-fuss perfect 90 degree bend in 15 inches of .063 is pretty cool.




The one thing that TCW did that I really did not want to do was they built their shelf by cutting their j-channel and unrolling it. Rather than severing the j-channel, I but a slight brake on a piece of .063 to account for the wall angle and bring a mounting plate onto the same plane as the shelf. This was a bit annoying to drill, but with a mirror and a right angle drill this was more than doable. Before deciding to go down this path, I debated how to rivet this for quite some time, Then I realized I still have that alligator crimper that I  bought off of ebay. The alligator crimper makes short work of this angle/orientation.



I still need to build a wedge and install some nut plates because the j-channel is not in the same plane as the battery box. That will be pretty straight forward though. (also, good use for those truck mats that I took out of my truck day 1!)

Oil and Fuel rail spacer

I guess the old hobbs meter oil pressure activated switch used to be smaller in diameter. The ones that I could find from Vans and on Aircraft spruce do not have enough clearance to be installed into the suggested location from Vans on the firewall. I was going to go with the showplanes engine mount switch bracket, but that adds another hose under your firewall. I ended up creating a couple of spacers for the standard rail. I was going to just fabricate an entirely new rail, but the only 6061 I had on the shelf that would have worked for this task was 6" x 1" which just seemed like a lot of work.

I made two 1/4" spacers which I will add some lightening slots into at some point when I find out how much I need to space the rail out.

Door epoxy voids

I feel like I was pretty careful (really careful) during my door skin bonding sessions. As careful as you can be, there are still some spots that are pretty hard to get a clamp on. And while I was so focused on the door perimeter, I did have a couple of voids in both the perimeter as well as the lock mechanism area. 

This was nothing that a little flox, epoxy, and some syringes from mcmaster could not fix. If I were to do the doors again I would be careful about the following things:

1) While this is in the instructions. Be extra careful that the cabin top flange is has the required 1/4 clearance from the door. I did end up with a small spot on the top side of the passenger door that I missed noticing that the door was resting on the cabin top flange. Not a big deal, but I think it did pull my door out of alignment a bit.

2) I left a fair amount of material outside of the scribe line around the perimeter of the door. In retro-spec I would have cut this back to the smaller distance so that I could see a little more of what was going.

3) Some of these things would be hard to clamp up, but areas like the door lock area could use some extra attention.

4) There is no need to over epoxy the parabeam. The result of this is a bit of a mess in a hard to clean up area that really needs to be cleaned up in order to not interfere with the door latching rods.

Nose fork tow-bar blocks

My mill is in the basement (heated) so I saved a lot of the small milling projects for the winter and this was a good day to start taking care of some of those things. Not that this was a hard project (nor does it require the mill) there was no reason not to have fun while fabricating.

I started by facing the blocks that were sent along from Vans.

I don't have a DRO on my mill (not yet) so Dykem and layout it was. I used a spotting bit to locate and start the 3/8" through hole.

You guessed it. I drilled a hole in the block. I did almost make a mistake here. I was about to counter-bore the hole to make it look a little more polished, but then I realized it is the actual bolt shoulder that the tow-bar (push-bar) is going to be attached to. 

After the through hole was in, I milled a set of parallel blocks to set the angles for the next four cuts. Complete.