Transponder in No Electrical System T-Craft

[DanBrown]

I'm a proud new owner of a 1940 BC-65. To base the ship closer to home, I'd need to put in a low power drain transponder (like the Becker unit) and encoder and a small (say 10 amp-hr) battery (take out of the ship to re-charge) to power it. Does anyone know a N-number of a Taylorcraft, Aeronca or similar airplane with such an installation that the radio shop could use their 337 as a model to speed field approval?

Dan Brown
Annapolis, MD

[mhorowit]

Re: Transponder in No Electrical System T-Craft

I'm a proud new owner of a 1940 BC-65. To base the ship closer to home, I'd need to put in a low power drain transponder (like the Becker unit) and encoder and a small (say 10 amp-hr) battery (take out of the ship to re-charge) to power it. Does anyone know a N-number of a Taylorcraft, Aeronca or similar airplane with such an installation that the radio shop could use their 337 as a model to speed field approval?

Dan Brown
Annapolis, MD

Dan - Bob Pagett who works out of Maryland Airport put a gell cell battery and xponder in a box and uses it in the ADIZ. Don't believe it's permenantly mounted, so no paperwork is necessary. I know I strap my gell cell down tight (in a box, with a fuse) to power my handheld. - Mike

[IslandGuy]

Re: Transponder in No Electrical System T-Craft

This is a neat idea http://www.basicaircraft.com/product_bpe14.htm
One of the fella's on this form linked me that site (thanks Darren). If I go transponder I'll probably get a generator, and something like this maybe http://www.aircraftspruce.com/menus/..._microair.html
I'm using a 1.8amp gelcell and seems to last a long time between charges. I know what your saying about the battery box Mike, but I just ended up putting heavy duty velcro on the battery bottom, and I need both hands to remove it! At the suggestion of a friend of mine, I made a wiring harness for the battery which powers my intercom, handheld, and I put a voltmeter in the system. Usually on a full charge it shows 13volts and when I see it dropping under 12v I know time for recharge. Gelcell's are cheap so pick up a small 1 amp for a spare and charge it every couple of months or so. It's not glamourous but it is tidy, lightweight and does the job quite nicely!
This all new to me and I really don't know much, except I know I'm having a blast with my TCraft!

[mhorowit]

Re: Transponder in No Electrical System T-Craft

I know what your saying about the battery box Mike, but I just ended up putting heavy duty velcro on the battery bottom, and I need both hands to remove it!

When thinking about mounting anything (i.e. battery) temporarily, try to visualize where it will end up if you practiced a spin. Just one more thing to worry about during what would be a frantic moment for me. - Mike

[IslandGuy]

Re: Transponder in No Electrical System T-Craft

I can't argue with you there!

[d.grimm]

Re: Transponder in No Electrical System T-Craft

Working with a friend on a PA-15 radio install (I know, it's not a T-Craft) and he has the wind generator that is STC'd. The rub is that the electrical system it connects to isn't, and no one in the FAA is willing to sign off on a electrical system install without a DER approval. (BIG BUCKS)
How can a encoder be signed off for 24 month check if it is not permanent installation?
Hope somebody can figure this out because it means a FREE heated hangar for me if I could do it.

[VictorBravo]

Re: Transponder in No Electrical System T-Craft

The rub is that the electrical system it connects to isn't, and no one in the FAA is willing to sign off on a electrical system install without a DER approval. (BIG BUCKS)


FREE heated hangar for me if I could do it.

Although not an electrician, I'll try to help get ANY Taylorcraft into a heated hangar!

Try this approach:

Get a letter from the manufacturer of your wind generator that one of the approved terminations of his wiring is a Molex plug, or an FAA approved two or four connector Cannon Plug.

Then make a wiring harness that connects your radio and your transponder and your encoder to the other half of that Cannon Plug. Use a protective sleeve over all the wiring, or an approved Mil-Spec cable with however many conductors you need... make it pretty, no tape or loose wires.

Make up a removable mount for the TXP/ENC that Velcro's or clamps on to something, again with no loose wires or electrical tape.

When the guy comes to test the transponder and encoder, have it clamped or Velcro'd or mounted in place, looking like it belongs there. It is not really his place to ask about how it is held in the airplane. the answer to his question about the static source is "this airplane was certified with a cockpit vent static source. There are no outside fuselage static ports on the Taylorcraft". I actually believe this is true, but check with Forrest or one of the other experienced rebuilders to see where the original altimeter static was located.

The first thing I'd do is to take the whole TXP assembl in to the test facility by itself and tell him it's a portable unit, and that you will be using it in more than one airplane, and to test it by itself. I don't know whether they can do that, but if they can you're home free. Otherwise have it in the plane loooking legit and just don't way anything about how it's mounted.

Tell him to hook up his static line to the fitting that is on the back of the encoder.

Let him run his test, and thank you very much.

When the IA comes out to annual the airplane (or the FAA asks whether that transponder intallation is approved), the answer is "There is no permanently mounted electrical system or electronic instruments in this aircraft, other than the wind generator which is approved under STC. This wind generator provides power to one or two portable hand held avionics for use whenever I operate in airspace that requires them. The rest of the time, those avionics are not carried in the aircraft."

This approach has a fairly good chance of preventing you from having any problems. Your "avionics" fall under the same category as a GPS that you can remove from your yoke mount. The FAA should not be able to complain about a GPS that clips in or out.

The important thing is to make your TXP/ENC look like a clean, neat, clip-in piece of optional equpment as possible, NOT a mess of loose wires and wire nuts strung all over the cabin.

[DanBrown]

Re: Transponder in No Electrical System T-Craft

Where does the transponder antenna go? Will it work through Stits System if installed in a self contained box?

Bill,

I got my private pilot instruction and check ride in Aeronca Champs at Whiteman from Hank Coffin of Coffin Air Service in 1956. Hank was reputed to be a WW I ace. The northen half of the Valley was sparsely populated at the time. Looks a bit different now.

[VictorBravo]

Re: Transponder in No Electrical System T-Craft

The TXP antenna should work fine through Stits, but the steel tubes may downgrade the performance a bit. Fortunately your transponder test technician will be close to the airplane when he tests it

Yes, the Valley is as crowded as downtown LA from the air. Our runway is not 90 degrees to the orientation when you flew here. Do you remember the 2 DeHavilland Mosquito bombers that were here back then? That was way before my time but the photos are still hung on the wall at the restaurant.

[M Jones]

Re: Transponder in No Electrical System T-Craft

Where does the transponder antenna go?

Dan,

Don't mean to be a smart ass, but If you're finished having children, it's OK to put it directly underneath the pilot's seat... I understand that there can be issues with the antenna location in that vicinity! It does radiate constantly at a freq. that may not be healthy.

[DanBrown]

Re: Transponder in No Electrical System T-Craft

Dan,

Don't mean to be a smart ass, but If you're finished having children, it's OK to put it directly underneath the pilot's seat...:

I could put it near my head -- that seems impervious to most outside influences.

Thanks to all for the suggestions. I'll be following them up and let you know if any progress.

Dan

[alwaysoar]

Re: Transponder in No Electrical System T-Craft

FAR-wise, why to you need a field approval for a radio installation? Why wouldn't a 337 be sufficient?

On another matter, I've seen BC-12D's with seats installed on a platform mounted to the seat frame that does not use the seat sling. Is this legal in any way shape or form?

Ed@BTV VT
TF 527

[Greg Bockelman]

Re: Transponder in No Electrical System T-Craft

Out of curiosity, why would you need a transponder/encoder? Unless you intend to fly into class B, you don't need it. And there are ways around Class C with a little prior planning.

[alwaysoar]

Re: Transponder in No Electrical System T-Craft

Well it would be nice where I live because if I want to fly due North I have to either pass through BTV airspace, fly waaaay out around BTV airspace over the middle of Lake Champlain, or climb over BTV airspace. I like to go into BTV sometime also. But I am more curious about why you need a field approval to install a radio and not just a 337-hope somebody replies.

[M Towsley]

Re: Transponder in No Electrical System T-Craft

Dan,

Have you looked at a dipole antenna? One you can mount to a crossmember behind the seat. No holes or reinforcements, etc. On the other hand, I have a waiver that I get signed by the FAA tower manager of the local Class C airport near home. Good for one year and I come and go as I please. It is contingent upon traffic congestion, but I have never been turned down yet. You obtain a form from them, have an A&P sign off that it is a non-electric aircraft since birth and give it to them. My request was turned around in a day. Another L-2 guy based at that airport operates his non-electric aircraft just this way, that is how I learned about it.