The International Cessna^® 170 Association

I'm not sure where to post this because it's not really a C170-specific topic, so here goes.

I was talking to my son tonight about some updates I made to the Stinson 108-2 I once owned. When I put a GPS/COMM unit in it (1999), I was trying to figure out where to place the GPS antennae. I looked above the cabin and there was the old ADF post still attached. I removed the post and, low and behold, the four mounting holes of the GPS perfectly aligned with the holes for the ADF post (from 1947) with a perfect ground plane in place. I mounted the GPS antennae, ran the coax into the headliner, down the door post and behind the panel to the unit. My son said, based on his Aviation Law class, I could have been written up for not getting a Field Approval. Should I have gotten a Field Approval for installing the antennae and the GPS unit?

You are lucky not to be in Levenworth

Ok first it is not illegal to do any darn thing you want to your aircraft. Your son won't find one regulation against it.

It is however be illegal to operate your aircraft with a standard airworthiness certificate after you do want you want if you are not licensed to perform the work or work under the supervision of someone who is and or that work is not done to accepted methods and practices an/or other wise approved methods.

Antenna installations are covered, at the very least, by AC 43.13. Under most instances, specially what you describe, this is a minor alteration. Minor alterations do not require a field approval, the wording you used for this thread.

All work of course must be properly documented.

SO if you were not licensed or working under the supervision of someone who was, you could be looking at time in Leavenworth for operation your aircraft after you performed maintenance and modifications you were not authorized to perform. If the work performed was not logged properly you and/or the licensed person overseeing the work could be looking at more hard time.

OK. I was working under the supervision of an AI, so I guess I'm covered. It was a long time ago and many brain cells have gone bye-bye since then (I didn't start out with that many, either).

Thanks for the clarification. I sold that airplane in 2001 and it's still flying, so I guess I didn't hurt it too badly.

In Leavenworth you could get a free shave, tho.

gahorn, yea and three meals a day plus a library. I hear they won't let you read Kitplanes because they're afraid you'll build an airplane and escape.

I'm sure that you must know that it is always easier to beg forgiveness than it is to get permissioin.

blueldr wrote:I'm sure that you must know that it is always easier to beg forgiveness than it is to get permissioin.

You must remember, though...this is the FAA we're talking about!

T. Gandy wrote:I'm not sure where to post this because it's not really a C170-specific topic, so here goes.

I was talking to my son tonight about some updates I made to the Stinson 108-2 I once owned. When I put a GPS/COMM unit in it (1999), I was trying to figure out where to place the GPS antennae. I looked above the cabin and there was the old ADF post still attached. I removed the post and, low and behold, the four mounting holes of the GPS perfectly aligned with the holes for the ADF post (from 1947) with a perfect ground plane in place. I mounted the GPS antennae, ran the coax into the headliner, down the door post and behind the panel to the unit. My son said, based on his Aviation Law class, I could have been written up for not getting a Field Approval. Should I have gotten a Field Approval for installing the antennae and the GPS unit?

You may not need a field approval, what you did does not qualify as a major modification, you did not change the airframe by using the pre-existing holes to mount the antenna,

That said, all maintenance must be entered in the aircraft's maintenance records, by a person qualified to return the aircraft to service.

see FAR 43.1 thru 43.9

T. C. Downey wrote:

T. Gandy wrote:I'm not sure where to post this because it's not really a C170-specific topic, so here goes.

I was talking to my son tonight about some updates I made to the Stinson 108-2 I once owned. When I put a GPS/COMM unit in it (1999), I was trying to figure out where to place the GPS antennae. I looked above the cabin and there was the old ADF post still attached. I removed the post and, low and behold, the four mounting holes of the GPS perfectly aligned with the holes for the ADF post (from 1947) with a perfect ground plane in place. I mounted the GPS antennae, ran the coax into the headliner, down the door post and behind the panel to the unit. My son said, based on his Aviation Law class, I could have been written up for not getting a Field Approval. Should I have gotten a Field Approval for installing the antennae and the GPS unit?

You may not need a field approval, what you did does not qualify as a major modification, you did not change the airframe by using the pre-existing holes to mount the antenna,

That said, all maintenance must be entered in the aircraft's maintenance records, by a person qualified to return the aircraft to service.

see FAR 43.1 thru 43.9

The only question I would have,Was the GPS was permanently mounted or temporarily afixed some fashion? If it was permanent, since he added electrical equipment and he must have swung the compass and documented that as well. The Equipment list must have been updated for the antenna installation, a W&B needed to be recalculated and a 337 needed to be done according to AC43.13 Electrical. But your AI knew all that so dont worry if he signed it off, your gold! D

canav8 wrote: The only question I would have,Was the GPS was permanently mounted or temporarily afixed some fashion? If it was permanent, since he added electrical equipment and he must have swung the compass and documented that as well. The Equipment list must have been updated for the antenna installation, a W&B needed to be recalculated and a 337 needed to be done according to AC43.13 Electrical. But your AI knew all that so dont worry if he signed it off, your gold! D

Still not sure why you would need a 337 for any of those items.

lowNslow wrote:

canav8 wrote: The only question I would have,Was the GPS was permanently mounted or temporarily afixed some fashion? If it was permanent, since he added electrical equipment and he must have swung the compass and documented that as well. The Equipment list must have been updated for the antenna installation, a W&B needed to be recalculated and a 337 needed to be done according to AC43.13 Electrical. But your AI knew all that so dont worry if he signed it off, your gold! D

Still not sure why you would need a 337 for any of those items.

Karl, any modification if the gps is permanent would warrant the 337 because of the electrical aspect. Sorry these are the plane rules of 43.13 of advisory circular. Your Mileage may differ and your IA may have a different opinion. Im telling you what I know and what is expected of me from my FSDO. Other FSDO's may not be so consciousness as mine. D

canav8 wrote: Karl, any modification if the gps is permanent would warrant the 337 because of the electrical aspect. Sorry these are the plane rules of 43.13 of advisory circular. Your Mileage may differ and your IA may have a different opinion. Im telling you what I know and what is expected of me from my FSDO. Other FSDO's may not be so consciousness as mine. D

Show me what constitutes a major modification of the electrical system. FAR 43-A

(xii) Changes to the basic design of the fuel, oil, cooling, heating, cabin pressurization, electrical, hydraulic, de-icing, or exhaust systems.

using an existing circuit does not meet the requirements

The avionics inspector at the SAT-FSDO (one of the pickiest FSDOs I've ever encountered) assured me in person that a Form 337 is unnecessary for a simple radio replacement or installation, and that a simple antenna installation on the primary cabin/fuselage or other non-critical area (meaning not on a fuel tank wall or flight control) on a non-pressurized aircraft is a minor alteration and simple logbook entry, and an update for the Wt/Bal and Equip. List and elect.load analysis. In fact, he expressed dismay at all the 337s he receives needlessly.
However, some avionics shops, often more familiar with installs on corporate jets and King Airs (pressurized aircraft) will be mounting antennas and wiring thru pressure bulkheads/skins/etc. and therefore need to document those major alterations on a Form 337. They may out of habit, generate similar paperwork on non-press'd aircraft needlessly.

Like I said, every FSDO regional office is different.