installing a transponder in a vintage aircraft

I have a 1942 Taylorcraft L2 that has no electrical system. I would like to install a transponder so that I can keep it at a class C airport. Having a panel or permanently mounted radio would also be nice.

The type certificate specifies three specific batteries, none of which seem to be made today. A wind generator is also specified in the type certificate. I have that model of wind generator but not the mounting equipment for it.

Before I contact the FSDO I thought that I would ask these questions here:

1. Can I install a battery other than the one specified in the type certificate? (I am thinking of an Odessy PC 680 or similar) If so, do I file a 337?

2. Assuming that the transponder will be TSO'd can I install it with a 337? I will probably go with a microair or similar small transponder with a low current draw.

Is there anything else that I should know? I want to identify all the "gotcha's" before I start this project.

Thanks

10 years ago I did the same thing. I put a Garmin SL60 COM/GPS/ICS, Garmin GTX327 and Basic Aircraft Products wind generator in a J-3 Cub. The inspector required that I have provisions to monitor the battery health, so I put in an Electronics International Volt/Amp meter. I also installed a solar recharge system to keep the battery topped off.

You will need to make a ground plane for the XPDR antenna. I used a circular piece of aluminum the radius of which was equal to the height of the XPDR antenna. It was pollytacked in place and I used ground strap to the airframe.

I use a 12V 12A Sealed Lead Acid Battery. It is not aviation certified. I asked my FSDO before hand and they said "43.13" - On my 337 I referenced it for the installation and they did not question my choice of battery. 2 years later I did a similar installation with a friend and he used a 12 V/7 A Sealed Lead Acid battery and they did not question that battery either.

The inspector had 2 comments on the installation: I needed to put the standard "GPS IS NOT APPROVED FOR IFR" placard in view of the pilot and he recommended that I drill a hole in the side of the wind alternator to install a hard mounted fuse, rather than the inline fuse I used. He was right on both counts. I can send you a complete package on my installation with copies of the 337's

Attachment 600

Pete

Pete, thanks for your response. If you have the paperwork you filed in electronic form it would be great if you could email it to me. I am sending you and email.

Tony

Hi,

I installed a Terra Transponder (TRT-250) in my 1941 Interstate S-1A Cadet which has no electrical system. The Terra installation Manual said that any power supply from 4 to 24 volts was useable, so my power supply is a 12 volt battery. I am an A&P and I.A. and did it on a 337 Form and received a Field Approval from my local FSDO.
I accomplished this installation in the early 1990's. I could send a copy of my 337 if you want.

Wayne

ok - send me your address and I will mail it - the drawings are on 11x17 paper.

Pete

weiskopf20@gmail.com

Could you please send me a copy of your drawings for the instalation of a radio and transponder in a Taylorcraft D-12
Gene Smith
9390 Tulane Rd.
Orange, Texas
77630

Quote:

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Originally Posted by N12tj

I have a 1942 Taylorcraft L2 that has no electrical system. I would like to install a transponder so that I can keep it at a class C airport. Having a panel or permanently mounted radio would also be nice.

The type certificate specifies three specific batteries, none of which seem to be made today. A wind generator is also specified in the type certificate. I have that model of wind generator but not the mounting equipment for it.

Before I contact the FSDO I thought that I would ask these questions here:

1. Can I install a battery other than the one specified in the type certificate? (I am thinking of an Odessy PC 680 or similar) If so, do I file a 337?

2. Assuming that the transponder will be TSO'd can I install it with a 337? I will probably go with a microair or similar small transponder with a low current draw.

Is there anything else that I should know? I want to identify all the "gotcha's" before I start this project.

Thanks

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I am trying to get together a design very similar to what you have described except that I plan on going with the Odyssey SJ16 battery which is a near ident equal to the PC680 but has an FAA granted PMA for its usage in aircraft. Mine is to be for an Aeronca Chief but I am going to go around the wind turbine in the belief that for the very small current draw of the new minaturized transponders, the dry mat batteries will provide sufficient power for much longer than the nominal flight durations of this kind of aircraft (IMHO) This approach has been utilized in high performance gliders successfully. It is my understanding that you(we) will require the assistance of an IA to qualify the installation. This is a maybe. I intend to use one anyway. There will be a requirement for a 337. Check out FAA Advisory Circular 43.9-1F which essentially walks you through the necessary steps to prepare the 337. It is available online. This approach means, of course, that I will have to recharge the dry mat batt at some interval. I hope to be able to do this with a trickle charger such as I currently use on my garden tractors and ATV, all of which are 12V systems. Please let me know if you make any significant discoveries as you go along particularly in the areas of acceptable SOC systems and recharge of dry mats. You may do so by posting here or, if you wish, make direct contact with me at tmail51a@gmail.com. Good Luck with your project.

EDGEFLY

Edgefly,

Thanks for sending that information. My current plan is to use some of the most recent technology, to include a low drain transponder, perhaps the Trig model which also supports ADSB squiter out, and a small low drain radio. Trig is developing one that is supposed to be out on Jan 13 and available through aircraft spruce as well as other outlets. Mr. Weiskoph was kind enough to send me a copy of his 337 for a similar installation that is pictured in a post above. I plan to use his basic plan.

I have put off this project for some time but plan on working on this issue withing the next few months. I would be interested in what you learn on your project as well.

My former PMI from the Renton, WA FSDO, has told me that an only an A&P with an Inspection Authorization (or other FAA Designees DAR, DER, etc) may sign block 7 Approval for Return to Service of a Form 337, so if I am right, the comments above suggesting use of an IA for a 337 is optional, are incorrect.
-Joel Marketello, A&P, IA

To All reading this thread. DO NOT READ MY 11/29/2012 AS IMPLYING A 337 COULD BE SIGNED OFF BY ANYONE OTHER THAN A PERSON ACCEPTABLE TO THE FAA ! I only meant to say that some portion of the work necessary to complete the installation could be performed under the guidance of a certified A&P or IA with his blessing. There is no question that the equipment and installation must fully comply with the applicable regulations of the FAR. I apologize for any misunderstanding my phrasing may have caused. N12tj, I will be happy to share with you any further information I become aware of in this regard.

EDGEFLY

The Odyssey battery is also used in a lot of motorcycles, where the conventional wisdom for good life seems to be that they do not like to be discharged more than about 50% of their ultimate capacity. Otherwise they have a very good reputation.

I am out of my league here - on the subject of batteries B U T my 2 cents worth. I wouldn't use the Odyssey motorcycle battery in this
particular installation. You do not need 600-800 cold cranking Amps as you will not have a starter. I would use a lightweight SLA (sealed
Lead acid) battery that goes for 1/3rd to 1/4th the cost. For a modern radio/gps/intercom/xpdr install you will only draw 3 - 5 Amps 90%
of the time and 2 Amps more in transmit (less than 10 % of the time). (Just off the top of my head numbers). A 12 Volt 12 Amp SLA will
give you about 2 hours service if the wind generator fails. If you do not uses a wind generator, a 15 or 18 Amp battery will give you another hour.

I have had good luck bringing abused SLA's back to life using a charger which has a Maintainer/Desulfate mode so I only replace the
battery every 5 years or so - not because they are weak, burt rather because I am proactive.

Also there is a weight savings and the SLA's can be mounted in any position - mine lays on its side under the rear seat.

Pete

I will suggest that for a modification to a certificated aircraft, your first sentence unfortunately sums it up. The path to success with an FAA field approval is easiest if you copy a mod that someone else has already had approved, and you use all FAA/PMA parts in a manner specified in AC43.13-1b. So the Odyssey SBS J-16, the FAA/PMA version of the PC680, has been approved by STC and 337 on a number of airplanes. So it is an easy sell to the FAA as part of your application. Presenting an SLA that has no FAA approval history will just make the process harder. I regularly do field approvals and in fact have the Odyssey approved for my Pitts S-2A. Great battery.

Looking at the technical details, in the case of an installation where there is no alternator and generator or starter, I agree that cold cranking amps is not the relevant requirement for the battery. But there will certainly be cases where the airplane will be away from a charger for longer than one flight. I will argue that in an installation with no alternator or generator, the hours of operation provided by the battery should be at least twice the fuel capacity of the airplane. That will allow the pilot/owner to go to his favorite fly-in, give a friend a ride, buy more gas, and fly home.

Looking at the mounting, the Odyssey can be mounted in any orientation. That said, look at AC43.13-2B (Alterations) where battery mountings are specifically described. Please plan on adding structure that will hold the battery secure in the event of a 9G forward load (15.4lbsx9 = 139lbs). I believe that the Super Cub approval placed the battery under a seat. Have not looked at the details but I will guess that the new battery tray attached to existing tubing. For my Pitts I used the existing battery tray.

I will note that the field approval paperwork package that goes to the FSDO should address every document suggested by AC43-210. Emphasize the increased safety aspect of the proposed modification. Address Instructions for Continued Airworthiness, the Certification Checklist, Weight and Balance, etc.

The electronic 337 form can be obtained at http://www.faa.gov/documentLibrary/m...orm/faa337.pdf

The electronic field approval checklist can be obtained at http://www.faa.gov/about/office_org/..._Checklist.pdf

For the Certification Checklist, to explain how you will maintain the conformance of the aircraft to the FAR's, go look at the Part 23 or CAR Part 3 sections that specify requirements for electrical systems.

Be patient and persistent. I just was told that I have a field approval signed off after 10 months of processing. Hope to see it in the US Mail this week.

Best of luck,

Wes
N78PS

I have a non-electric antique Piper J4-A just signed off, that really for my flight instruction (receiving) should have some sort of intercom and traffic monitoring capability. I was thinking of making up a package of an ICom handheld set to 122.8, an RST intercom which has been modified to supply power to my ANR headset, combined with a sealed 7AH lead acid battery out of a line loss UPS. This would be mounted in the baggage compartment of the J4A with velcro. The +12 VDC Power would be supplied to the intercom, the ICom radio, and to the ANR headset that I have. That static drain of everything is under 100 ma unless transmitting which raises it to ~500 ma. I assume the only thing mounted to the aircraft would be the velcro pads. Is this pushing the intent of the regs too much?

Thoughts?

As you are essentially assembling a large "hand-held" radio, that assembly should be fine. You are not "permanently" attached to the airplane. Where the original poster is stuck with getting into FAA paperwork is the transponder. I am not aware that you can legally have a portable transponder. I would love to be wrong. And if you add a transponder to your portable rig in an unapproved manner, please do not post it on the internet.

That said, the original poster is not breaking new ground. If you are a member of a type club, ask who has already gotten an approval for the installation that you want. Most folks who have worked through the FAA paperwork are happy to share. One of hte satisfactions in life is helping other folks avoid pain that you have experienced. But you gotta "wanna" enough to persevere.

Best of luck,

Wes
N78PS

The Odyssey SBS J-16, looks like a winner and if I was starting over I might consider use it. The internet listing I came up
with has it for $176. The SLA that I am using, and which is approved by the FAA on a signed 337 was only $45.

Pete

That's great, which battery? I will note that my FSDO is exceptionally picky, and each FSDO is its own FAA, so what is OK in your region may not fly in mine. That drives me towards FAA approved components for my mods. Don't know what FSDO the original poster will work with. Hope they are easy to work with.

I will note that after working through the FAA field approval process (time x $$), the actual cost of the battery really does not matter.

Thanks,

Wes
N78PS

I used the Panasonic PS 12120L. It is no longer made but sevceral companies make a replacement.

The "it is no longer made" is a problem. The field approval specifies the exact make and model battery that is approved. If you can no longer obtain that exact battery, you are technically required to do a new field approval for the new make and model battery. Product life is one factor that goes into choosing the parts that you select for a modification.

Best of luck,

Wes
N78PS