PMA Questions

Mike Granby wrote:

Indeed. But is there such a thing as an STC for a minor modification?

Unless I'm misunderstanding something, you're talking about two
different things. A 337 is for a major repair or alteration as defined
in 43 Appendix A. An STC is issued for a *design* modification. So
yes, you can be issued an STC for a minor design modification. 337's
and STC's aren't necessarily tied together, although they often are.

Is there any situation in which a vendor might choose to use an STC to
get a part on to his PMA, but where the existance of the STC does not
per se render the change major and thus in need of a 337?

I don't think it works that way. An STC isn't something you choose to
use, it's either required or not. PMA parts, as far as I can think,
have nothing to do with it.

Just the uneducated opinion of an non-experienced A&P who lets other
people worry about this stuff. Actually, I went to a conference on
aircraft certification last year and can't remember any of it. Should
have taken notes.

Unless I'm misunderstanding something, you're talking about two different things. A 337 is for a major repair or alteration as defined in 43 Appendix A. An STC is issued for a *design* modification. So yes, you can be issued an STC for a minor design modification. 337's and STC's aren't necessarily tied together, although they often are.

Well, as a for-instance, suppose I got tired of paying $700 for a five
dollar microswitch, and decided that Cessna's slit-in-the-wing was a
perfectly adequate stall warning. When my Archer's stall warning switch
goes TU, I want to replace it ("augment it") with the slit-in-the-wing
(and while I'm at it, put in a five dollar microswitch from Radio Shack
in the original place as a backup.

3777? STC?

Jose
--
You can choose whom to befriend, but you cannot choose whom to love.
for Email, make the obvious change in the address.

Yes, the SOROS Cessna replacement vent tubes are an example of this.
This is a minor alteration not needing a 337 form (Major Alteration or
Repair), but incorporating an STC in constrast to a PMA to get parts
manufacturing approval.


On 6 Dec 2005 15:18:23 -0800, "Mike Granby" wrote:


Indeed. But is there such a thing as an STC for a minor modification?
Is there any situation in which a vendor might choose to use an STC to
get a part on to his PMA, but where the existance of the STC does not
per se render the change major and thus in need of a 337?

"Jose" wrote in message ...
Unless I'm misunderstanding something, you're talking about two different things. A 337 is for a major repair or
alteration as defined in 43 Appendix A. An STC is issued for a *design* modification. So yes, you can be issued an
STC for a minor design modification. 337's and STC's aren't necessarily tied together, although they often are.

Well, as a for-instance, suppose I got tired of paying $700 for a five dollar microswitch, and decided that Cessna's
slit-in-the-wing was a perfectly adequate stall warning. When my Archer's stall warning switch goes TU, I want to
replace it ("augment it") with the slit-in-the-wing (and while I'm at it, put in a five dollar microswitch from Radio
Shack in the original place as a backup.

3777? STC?

Jose
--
You can choose whom to befriend, but you cannot choose whom to love.
for Email, make the obvious change in the address.

You could engineer up a repair and submit it to a DER for approval...

PMA parts, as far as I can think,
have nothing to do with it.

The FAA document on PMAs says there are two ways of getting a
installation included on the PMA's eligibility list. One is to make the
part identical to an original part, and the other is to have an STC for
the installation of that part. Hence, I was wondering if this PMA
requirement resulted in people getting STCs for changes that would not
otherwise require them.

This is a minor alteration not needing a 337 form
(Major Alteration or Repair), but incorporating an STC

Interesting! I'll dig into that. I did notice that AC21-40, which is
only an advisory circular and thus not regulation per se, says that
"STC's are not issued for minor changes or for approval of
replacement and modification parts meeting the provisions of 14 CFR
part 21, section 21.303", though, so where does that leave us???

From Soros website...

Q. How is the Ventube installation recorded? A. If installed by an AI,
they can make the appropriate aircraft log book entry and complete the
FAA Form 337. If the owner installs the Ventube, he can make the entry
in the aircraft log book and have his AI sign off and complete the FAA
Form 337 at the next annual."

Quite where they're getting this from, I'm not sure! I thought 337's
were due 48 hours from return-to-service?

"Why, that was there when I bought the airplane..."

Jim



"Jose" wrote in message
...
Unless I'm misunderstanding something, you're talking about two different
things. A 337 is for a major repair or alteration as defined in 43
Appendix A. An STC is issued for a *design* modification. So yes, you
can be issued an STC for a minor design modification. 337's and STC's
aren't necessarily tied together, although they often are.

Well, as a for-instance, suppose I got tired of paying $700 for a five
dollar microswitch, and decided that Cessna's slit-in-the-wing was a
perfectly adequate stall warning. When my Archer's stall warning switch
goes TU, I want to replace it ("augment it") with the slit-in-the-wing
(and while I'm at it, put in a five dollar microswitch from Radio Shack in
the original place as a backup.

3777? STC?

He's out of his tree. There are now a couple of different companies
that make replacement blades for the more popular Bell helicopters -
completely PMA'd parts. But you are still going to need a heck of an
STC in order to mount one on your Cessna 172. G

If I just had to guess, I would say that where he got confused is that
if you are replacing a part on your aircraft with a part that is a
PMA'd *replacement*, then you don't need an STC. But that's because
it's already covered by the TC (or by a previous STC). The PMA says,
in effect, you can treat these parts as APPROVED parts (including
approved replacement parts). Doesn't necessarily mean you can stick it
on your plane anywhere you feel like.

RST Engineering wrote:
"Why, that was there when I bought the airplane..."

Now get that **** out of there and put in the right part.