installing a transponder in a vintage aircraft

[nrpetersen]

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.

[weiskopf20@gmail.com]

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

[WLIU]

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

[nrpetersen]

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?

[WLIU]

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

[weiskopf20@gmail.com]

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

[WLIU]

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

[weiskopf20@gmail.com]

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

[WLIU]

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