Re: Is a 337 reqd *only* for major mods?
- From: Michael <usenetreplies@xxxxxxxxxxxxxxxxxxx>
- Date: Mon, 31 Mar 2008 10:37:02 -0700 (PDT)
On Mar 31, 3:55 am, Peter <nos...@xxxxxxxxxxxxxx> wrote:
I've read FAR 43 Appendix A which lists major mods, and some other
material suggesting a 337 is only required for major mods.
Is this correct?
Correct. A minor mod requires only a logbook entry signed by an A&P.
For example would you apply for a 337 approval if installing a
voltmeter in the panel?
That depends on which FSDO you are in, and what their policy is that
particular year. John Dupre has already written you a pretty good
reply and I won't go over the same ground he did, but I'll add
something. Mostly, you need to understand that the rules don't matter
- the FAA people mostly don't understand them anyway. What matters is
what your mechanic will sign off, and what your IA will accept come
annual time.
Alterations often involve installing something - yours does. Let's
assume for the moment that nothing is being removed.
For a major alteration, there is not much gray involved - you need
approved data for both. That means TC/STC or a field approval. Most
FSDO's are not doing field approvals anymore (except for GPS
installations) so you will need a DER. Be prepared to pay and pay and
pay...
For a minor alteration there are two issues involved - what you are
installing, and how. Let's deal with the what first.
The what needs to be an aircraft part. That means it needs to have a
PMA, TSO, a litsting on the TC, etc. Or it can be a standard part.
That gives you a lot of leeway, because a standard part is one
manufactured to a standard maintained by the government (such as a Mil-
Spec), or industry standards body. If not, you're back in major
alteration territory. Your reference:
14CFR21.303 Replacement and modification parts.
(a) Except as provided in paragraph (b) of this section, no
person
may produce a modification or replacement part for sale for
installation
on a type certificated product unless it is produced pursuant to a
Parts
Manufacturer Approval issued under this subpart.
(b) This section does not apply to the following:
(1) Parts produced under a type or production certificate.
(2) Parts produced by an owner or operator for maintaining or
altering his own product.
(3) Parts produced under an FAA Technical Standard Order.
(4) Standard parts (such as bolts and nuts) conforming to
established industry or U.S. specifications.
Of course a lot is left to interpretation. If a voltmeter a standard
part? What if it's an automotive part and built to an SAE spec? That
seems to be in conformance to 14CFR21.303(b)(4) but few A&P's will see
it that way.
Then there's 14CFR21.303(b)(2) - the owner produced part. Good luck
with that one. Jim Weir will tell you it's OK - but most A&P's will
not install something you built unless it's a copy of a certified
part.
If it has a PMA - even for another airplane (the Magellan 5000-series
aviation GPS used to be sold with a Beech PMA, and that was good
enough) or is TSO'd then you can install it in an airplane. But can
you install it in YOUR airplane? And how?
For something like a voltmeter, it's pretty easy. AC 43-13 already
includes lots of guidance on making electrical installations - how to
route and size wires, check for interference, etc. The panel probably
has a space for it.
So bottom line, you can probably find an A&P to sign off the
installation of a voltmeter as a minor mod (heck, if you're in the
Michigan area, I'll sign it if you install it) but now comes your
second hurdle. Will your IA accept it?
If he doesn't, he doesn't actually have to tell you to pull it out.
He can simply be helpful and ask the FSDO. How do you think that one
is going to go?
Some FSDO's would consider this a major mod, others a minor one, and
that's just the way it is. For FSDO's that consider it a major mod,
some will accept the TSO'd installation instructions for the voltmeter
(assuming it has them) as approved data, others will say it's only
acceptable data and only the basis for getting a field approval. A
few will still issue the field approval, others will send you to a
DER.
No standardization, no certainty.
Michael
.
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