Aft fuselage wiring and component placement

Trying to see if anyone cares to share photos or how to tips. I'm scratching my head on smartest/best layout of the wiring needs that go after through fuselage and the wiring to the tail. Also where to best locate the ELT, and I bought all Garmin products, GMU magnometer and the remote transponder.

Anyone done this can care to share what best solution is?

https://www.dropbox.com/s/lcr7o6o1rvmh51h/IMG_0954.jpg?dl=0
https://www.dropbox.com/s/zi45m9ian6i0kaw/IMG_0983.jpg?dl=0

The UK LAA were not keen on letting me drill holes in the longerons despite van's assurances that it was fine, so I used an EarthX battery, mounted it lengthwise, and redesigned the battery box floor (0.070 aluminium) to accommodate some of my avionics and ELT. The battery is held down with an aluminium strap, and the avionics bolted to the floor and also bridged from the top to the mid longeron, using existing holes for the rear luggage/battery box cover. It is absolutely solid, still ways less than a standard battery (2lbs) , and C of G is not altered.
I'm putting my magnetometer in the starboard outer HS tip.. there is enough room if you use a 90 degree D-sub connector, and it is miles away from any steel or electric device.
I surveyed the whole aircraft looking for a magnetically isolated location. i know others have used the aft deck under the HS, but it is only 2 feet away from the pitch trim, and 4 feet away from the pitch AP servo, and surrounded by loads of steel bolts!
Works for me... and the cable run through the HS in front of the ribs was easy.
I've just had formal approval for the avionics shelf mod from the LAA

As I have a fixed pitch prop (Catto) and a lightweight gear (Grove), I`ve decided to mount the battery (Earth-X) on the firewall. Thus in my aft fuselage is only the Pitch Servo and the remote Transponder. For the GMU-22 I made a shelf between the upper longerons. Along those upper longerons I have installed small "L" brackets with plastic bushings which hold the Magnetometer cables and the static line. Along the lower longerons I have as well those brackets and they are used for the taillight and electric pitch trim cables. I split those two to get as much physical distance between electric cables and the RS-232/RS-485 for the Magnetometer.
The XPDR antenna cable is routed straight back to the antenna. Check the minimal antenna length for the XPDR!









PS: This is not the latest status, the bolt which holds the adel clamp (for the servo cables) at the pitch servo was changed to a drilled head version and is safety-wired to the servo, loctited and uses a metal stop nut. I know overkill but if this bolt would come loose it could possibly jam my pitch control.

YvesCH,
I totally appreciate this photo of your remote transponder! I like your "minimalist" approach to the bracket for that, and its to the side, allowing option for something else on the other side.
This is great! Very much appreciate you sharing.
Would you do anything different on the GMU-22 mounting if you had to do it again?
And sorry, but what do you mean by "Check the minimal antenna length for the XPDR!"

Greatly appreciated.

Huskyhipdoc,
Very well. Not too bad at all on the lateral stacking of all three. I am wanting to put the same components there as well. I just didn't want to be excessive on the brackets and mounting fixture. Thanks for sharing this pic....I am thinking I can study those and maybe minimize some of the metal work. Anyways, very helpful.

Question, if you had to do this again, would you do anything different.
I have been contemplating putting those components instead aft of that bulkhead. Whats your opinion on that? Or would you say, "Nope, better is right there as in the photo?

ksdflying
I'd do the same again, largely because of the difficulties convincing our LAA that drilling holes in the longerons wasn't regarded as an issue with Van's.
keeping them on board over something simple might be useful if I start to change something more radical!
Although the C of G effect is negligible, I was concerned about increasing the angular moment of inertia by mounting more weight further back than where we know it is safe; too many aircraft have entered unrecoverable spins because the altered angular rotation forces changed with small items placed at the rear.
This was easy to do, and the mount fixes to the lower baggage floor as well as existing longeron holes, and the total weight is still less than a standard battery. the 'eureka' moment for me was changing the orientation of the battery! Simple stuff, in retrospect!
The upper bracket really locks everything in position, otherwise its a bit 'tall' as an installation.

The vertical face of the rear baggage removable shelf isnt at 90 degrees to the floor, so a bit of fiddling was required to make it all fit!

ksdflying said:

YvesCH,
I totally appreciate this photo of your remote transponder! I like your "minimalist" approach to the bracket for that, and its to the side, allowing option for something else on the other side.
This is great! Very much appreciate you sharing.
Would you do anything different on the GMU-22 mounting if you had to do it again?
And sorry, but what do you mean by "Check the minimal antenna length for the XPDR!"

Greatly appreciated.

Click to expand...

So far I am very happy with the setup but I am not yet flying. The location of the GMU-22 was suggested by Christer from Steinair who has mounted it at the same location.

With the „check the minimum required antenna length for the transponder“ I ment something else and wrote it wrong. In the installation manual of my GTX-23ES its written:

2.3.2 Antenna Installation Considerations:

d. To prevent RF interference, the antenna must be physically mounted a minimum distance of three feet from the GTX

As you have minimal spacing between the antennas and on the RV-8 you can barely mount antennas on top of the aircraft you really should check if you can achieve those requirements. My Installation fulfills al of those but it took quite some time to find a suitable spot for all of them


And yes I once planned to attach a oxygen bottle on the other side of the XPDR but did not yet do so... Maybe in the future...
The other advantage of my setup is that you can easily slide out the Transponder by only removing the rear baggage shelf. Further it does not block the view to the elevator bellcrank. I plan to install e sightglass for the elevator bellcrank as Luca Perrazoli did..

YvesCH,
Awesome! Huge thank you for your help. Appreciate that added note about the Oxy bottle is good too.
Got it! And yes, reading my garmin install manual and reading all the limitations is what was puzzling me. Thanks for adding this notion. Duelly noted.
This is the help I was looking for.
Thank you for sharing.

I was going to put my oxygen bottle behind the rear seat baggage too.. then got worried about it sitting next to the EarthX battery. In the unlikely event of a runaway thermal issue, I don't want the cylinder next to it!.

I can appreciate that concern. Interesting point.

GMU-22

Yves, concerning the shelf, between the longerons,
for the GMU-22, which number bulkhead is it near?

thanks!

FlyGood said:

Yves, concerning the shelf, between the longerons,
for the GMU-22, which number bulkhead is it near?

thanks!

Click to expand...

I looked, his GMU-22 is Forward side of F-809-1 bulkhead.
I discovered that there is a drawing for the GMU-11 best placement per the OEM fyi.