I gave a presentation on this subject of avionics wiring at the 2007
SSA convention. See http://derosaweb.net/aviation/presentations to
download the presentation. It looses a little without my voice over
but you will get the main points. Darryl - Please critique this if you
get a chance.

Couldn't agree more on the use of tefzel. It is an FAA requirement,
not an option. I have seen lots of incredibly lousey glider wiring so
I am on a "jihad" to get the word out to do better. Remember that
your local DIY or electronics store does *NOT* have an aviation
aisle. http://wingsandwheels.com/page5.htm has a good assortment of
Tefzel as well as places like Aircraft Spruce and Wag Aero.

Using rules of thumb on wire gauges can lead to mistakes. Should the
main line from the batteries to the instruments be 12 gauge?
Smaller? Larger? It all depends on the load. In a airplane (versus
an glider) this can go from little to massive, so determining the
gauge needs some careful analysis. Luckily the load of the avionics
package in a typical glider is fairly standard (vario, computer/
recorder, PDA, transceiver) so 12 gauge is generally considered OK.
I haven't analyzed the typical loading of a transponder so cannot
comment further.

Other control (ptt, gear warning) and audio (speaker, microphone) are
low current affairs so I typically using 22-24 gauge which you can
find in multiple wire bundles.

Finally, my disclaimer. I am *NOT* a FAA certified avionics
technician. I cannot sign a log book for a repair or perform the
installation. You need to get your work done by, or overviewed by, a
FAA licensed tech. Nuff said.

My $0.02.

- John DeRosa