337 to install a transponder?

I just purchased a Garmin GTX-327 off of Ebay (installed for one day, before
the owner decided he REALLY wanted the Mode S GTX-330!), and am lining up
installation. I was surprised to hear that a 337 form had to be filed for
this installation.

It's not a big deal for the avionics shop to do, but wouldn't you think
Garmin would have STC'd this unit for the Cherokee line?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck wrote:
I just purchased a Garmin GTX-327 off of Ebay (installed for one day, before
the owner decided he REALLY wanted the Mode S GTX-330!), and am lining up
installation. I was surprised to hear that a 337 form had to be filed for
this installation.
It's not a big deal for the avionics shop to do, but wouldn't you think
Garmin would have STC'd this unit for the Cherokee line?

Having an STC isn't really the issue. It's whether a particular shop (or
a particular FSDO) considers the installation a "major alteration" or a
minor one. There a probably shops that would swap two similar
transponders with just a logbook entry, but most would probably do a 337
just to cover themselves. Heck, my buddy's avionics shop does a 337 for
practically anything it does.

-- Jay


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Jay Honeck wrote:
I just purchased a Garmin GTX-327 off of Ebay (installed for one day, before
the owner decided he REALLY wanted the Mode S GTX-330!), and am lining up
installation. I was surprised to hear that a 337 form had to be filed for
this installation.

It's not a big deal for the avionics shop to do, but wouldn't you think
Garmin would have STC'd this unit for the Cherokee line?

Even if there is an STC for the cherokees you would still need to file a
337. If there isn't an STC, if installing a transponder is considered a
major alteration, then you would need a field approval. So you send the
337 to the FSDO for approval before installation, when the approval
comes back you install the transponder. After installation and IA
signoff you send the 337 back to the FSDO. They then forward it down to
OKC for it to go into the permanent records of your aircraft.

Gene Kearns wrote:

Frankly, I don't think anything about a transponder rises to the level
of a Major Alteration... ditto radios, intercoms, etc.

A panel mount GPS is a major alteration. The back of the 337 is an
unreadable mess only a government agency could come up with. And mine
was a slide in replacement for a Loran.

"Jay Honeck" wrote
I just purchased a Garmin GTX-327 off of Ebay (installed for one day, before
the owner decided he REALLY wanted the Mode S GTX-330!), and am lining up
installation. I was surprised to hear that a 337 form had to be filed for
this installation.

It's not a big deal for the avionics shop to do, but wouldn't you think
Garmin would have STC'd this unit for the Cherokee line?

It's not likely that the unit is STC's for the Cherokee line, but you
can check easily enough. www.airweb.faa.gov/stc

By definition, if an STC is required, then the alteration is major.
That means a Form 337 is required. The STC also constitutes approved
data.

If no approved data are available, you also need a field approval
(which is almost impossible to get these days).

In general, avionics are installed on a Form 337. This should not be
necessary. There is FAA guidance that explicitly states that the
installation of a single radio in a non-pressurized airplane is a
minor alteration, but many (most) FSDO's feel otherwise. So without
an STC, what kind of data do we use? Well, mostly we wing it.

The avionics are TSO'd, and that means the installation manual is
TSO'd as well. A TSO'd manual is approved data. So we cite the
installation manual and the relevant (sometimes barely relevant) parts
of AC 43.13 as the data, and call it good. Most FSDO's seem to be
happy to accept this. Is it really legal? Probably not, but it works
so we don't make too many noises about it.

What your shop is doing is normal practice. Leave it be.

Michael

What your shop is doing is normal practice. Leave it be.

Thanks for the wisdom and input.

As always, I am in awe of the knowledge available on this newsgroup, and the
ignorance of the FAA -- in equal measures! :-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

So you send the
337 to the FSDO for approval before installation, when the approval
comes back you install the transponder.

The seller is shipping the unit today, but (of course) we're coming up on
Xmas and New Years, and the avionics shop is in Illinois, so it'll probably
be at least a week before I could get the installation done anyway.

How long does getting the 337 usually take?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

On Thu, 18 Dec 2003 18:06:12 -0500, Gene Kearns
wrote:

On Thu, 18 Dec 2003 22:44:22 GMT, Newps wrote:



Gene Kearns wrote:

Frankly, I don't think anything about a transponder rises to the level
of a Major Alteration... ditto radios, intercoms, etc.

A panel mount GPS is a major alteration. The back of the 337 is an
unreadable mess only a government agency could come up with. And mine
was a slide in replacement for a Loran.

W&B issues and possibly IFR issues aside, this might have been,
arguably, preventive maintenance that you could have accomplished,
yourself. FAR Part 43, Appendix A(31)...

After a telephone call to AOPA, I find that I'm not the only one that
has trouble with this. The best they could suggest is that an
installation requiring more or less amperage draw than the last
installation has been considered by some FSDOs a "change to the basic
design of the ...electrical...system. I say, "bovine scatology" and
I'm 99.99% sure my avionics PMI would agree...... but then each FSDO
is its own domain...

Take a look at:

http://www1.faa.gov/asd/internationa...C/AC20-138.pdf

7. AIRWORTHINESS CRITERIA FOR GPS INSTALLATIONS USED AS A SUPPLEMENTAL
NAVIGATION SYSTEM LIMITED TO VISUAL FLIGHT RULES (VFR) ONLY.
a. Application Process. Operators wishing to obtain approval of Class A() GPS equipment limited
to VFR use only may do so via the type certificate (TC), supplemental type certificate (STC), or, for equipment
previously approved via the TC or STC process, data approved by the FAA (responsible Flight Standards
District Office) on FAA Form 337, Major Repair and Alteration. The approval for return to service must be
signed by one of the entities noted in 14 CFR part 43; i.e., repair station, manufacturer, holder of an inspection
authorization, etc.

8. AIRWORTHINESS CRITERIA FOR GPS INSTALLATIONS USED AS A SUPPLEMENTAL
NAVIGATION SYSTEM UNDER INSTRUMENT FLIGHT RULES (IFR).
a. Application Process. Operators wishing to obtain approval of Class A() GPS equipment for IFR
operations may do so via the type certificate (TC) or supplemental type certificate (STC) process. For
equipment produced under TSO-C129 authorization that has previously obtained initial installation approval
via the TC or STC process, approval may also be obtained via data approved by the FAA (responsible Flight
Standards District Office) on FAA Form 337. The approval for return to service must be signed by one of the
entities noted in 14 CFR part 43; i.e., repair station, manufacturer, holder of an inspection authorization, etc.

I wouldn't say it is the only means of "approving" a GPS install, but
it's definitely the one a FSDO is going to wave in your face.

Regards;

TC

Gene Kearns wrote:

W&B issues and possibly IFR issues aside, this might have been,
arguably, preventive maintenance that you could have accomplished,
yourself. FAR Part 43, Appendix A(31)...

Yeah, I wish. We called FSDO and asked. He said a 337 was necessary.
He even faxed over a copy of what he wanted to see. So we swapped out
the info on the 337 with my info and sent it right back.

In article YnsEb.395597$Dw6.1246219@attbi_s02, "Jay Honeck"
wrote:

So you send the
337 to the FSDO for approval before installation, when the approval
comes back you install the transponder.

The seller is shipping the unit today, but (of course) we're coming up on
Xmas and New Years, and the avionics shop is in Illinois, so it'll
probably
be at least a week before I could get the installation done anyway.

How long does getting the 337 usually take?


While overhauling my engine I did a set of six 337s by talking
to the FSDO guy in advance and then brought the 337s over to
the office prior to the post-engine install test flight. In
other words, it didn't take any time.

--
Bob Noel