PMA Questions

[Mike Granby]

I wonder if anyone can answer a few questions I have regarding PMAed
parts? Suppose I have a part I wish to install on a certified aircraft.
Are the following statements true or false?

1/ If the part is PMAed and the airplane is in the eligibility list,
and the PMA was obtained by virtue of the part being identical to the
original TC holder's design, the part can be installed by an A&P with
a logbook entry.

2/ If the part is PMAed by virtue of an STC which includes the airplane
in its approved model list, the part can be installed, but it must be
documented using a Form 337 which must be signed by an IA.

3/ If the part is PMAed virtue of an STC which does NOT include the
airplane in its approved model list, it MIGHT be possible to get the
part installed, but it must be done via a form 337 and a field
approval.

4/ If the part is not PMAed, it cannot be offered for sale for
installation of a certified aricraft per 21.303 unless it is TSOed, a
standard part etc. It might however be possible to get it installed
using a field approval.

Thanks in advance for any light you can shed on this...

[Bill Zaleski]

Yes, on all four items.

Bill A&P IA


On 5 Dec 2005 18:38:57 -0800, "Mike Granby" > wrote:

>
>I wonder if anyone can answer a few questions I have regarding PMAed
>parts? Suppose I have a part I wish to install on a certified aircraft.
>Are the following statements true or false?
>
>1/ If the part is PMAed and the airplane is in the eligibility list,
>and the PMA was obtained by virtue of the part being identical to the
>original TC holder's design, the part can be installed by an A&P with
>a logbook entry.
>
>2/ If the part is PMAed by virtue of an STC which includes the airplane
>in its approved model list, the part can be installed, but it must be
>documented using a Form 337 which must be signed by an IA.
>
>3/ If the part is PMAed virtue of an STC which does NOT include the
>airplane in its approved model list, it MIGHT be possible to get the
>part installed, but it must be done via a form 337 and a field
>approval.
>
>4/ If the part is not PMAed, it cannot be offered for sale for
>installation of a certified aricraft per 21.303 unless it is TSOed, a
>standard part etc. It might however be possible to get it installed
>using a field approval.
>
>Thanks in advance for any light you can shed on this...

[Ron Natalie]

Mike Granby wrote:
> I wonder if anyone can answer a few questions I have regarding PMAed
> parts? Suppose I have a part I wish to install on a certified aircraft.
> Are the following statements true or false?

PMA is authority to manufacture (or demonstration that part has been
legitimately manufactured if you wish).

>
> 1/ If the part is PMAed and the airplane is in the eligibility list,
> and the PMA was obtained by virtue of the part being identical to the
> original TC holder's design, the part can be installed by an A&P with
> a logbook entry.
>
Correct, the TC is the authority to install the part. Since you are
putting things in conformance with the type certificate, it is not a
major modification. A 337 is hence not required, just the normal
log entires.

> 2/ If the part is PMAed by virtue of an STC which includes the airplane
> in its approved model list, the part can be installed, but it must be
> documented using a Form 337 which must be signed by an IA.

Correct, An STC is a major modification, you need to file a 337 with the
STC as the approved data.

>
> 3/ If the part is PMAed virtue of an STC which does NOT include the
> airplane in its approved model list, it MIGHT be possible to get the
> part installed, but it must be done via a form 337 and a field
> approval.

Correct, in most cases. If the change is a major modification, you
need to file a 337 for a field approval. The STC is pretty good
approved data and the PMA shows the part is manufactured to reasonable
standards, but the FAA (or a delegate) must verify this.

If the change is not a major modification, then you can forgo the
337.

>
> 4/ If the part is not PMAed, it cannot be offered for sale for
> installation of a certified aricraft per 21.303 unless it is TSOed, a
> standard part etc. It might however be possible to get it installed
> using a field approval.

....Really the same as #3. If it's a major modification and you
provide "data acceptable to the administrator" the field approval
is a possibility. If it's not a major modification, you can just
install the part.

[jmk]

Bill and Ron gave you good information. Think of the PMA as simply a
statement that the part is an approved substitute for the part from the
OEM that is being replaced.

One minor issue - a company can make a part and get an STC without
getting the PMA. It can then be installed *by the manufacturer* but it
can not be "offered for sale for installation on a certificated
aircraft" by someone else. For example, when GAMI was working on their
injectors, the FAA would not accept a PMA application until the STC had
been issued. So for a time they had the STC but not the PMA. They
could make the injectors and sell them to you, but THEY had to install
them. Once they got the PMA as well, then they could just mail them to
your local A&P for installation.

jmk

[Mike Granby]

Thanks to everyone for their replies. The reason I brought this up is
that I am engaged in a discussion with someone on a Pipers discussion
group, and he is asserting that a PMAed part can be installed without
further approval or paperwork, whether or not the PMA was obtained as a
result of identicality, or as a result of an STC. My understanding that
was that STCed parts needed a 337 and an IA, and that the PMA had
nothing to do with it, other than meeting the requirements of 21.303
for offering parts for sale.

[.Blueskies.]

"Mike Granby" > wrote in message oups.com...
>
> Thanks to everyone for their replies. The reason I brought this up is
> that I am engaged in a discussion with someone on a Pipers discussion
> group, and he is asserting that a PMAed part can be installed without
> further approval or paperwork, whether or not the PMA was obtained as a
> result of identicality, or as a result of an STC. My understanding that
> was that STCed parts needed a 337 and an IA, and that the PMA had
> nothing to do with it, other than meeting the requirements of 21.303
> for offering parts for sale.
>

Yes, the STC requires the 337 for installation on the airframe in question, but the maintenance of that STC can be done
just like any other maintenance; install OEM, PMA or owner produced parts signed off by an A&P.

[Mike Granby]

Don't you need an IA to sign the "Return to Service" box of the 337?

[Newps]

Mike Granby wrote:
My understanding that
> was that STCed parts needed a 337 and an IA,

Yes, always.

[Rachel]

Newps wrote:
>
>
> Mike Granby wrote:
> My understanding that
>
>> was that STCed parts needed a 337 and an IA,
>
>
> Yes, always.

Unless the 337 is signed by a manufacturer or repair station....

[Mike Granby]

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?

[Rachel]

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.

[Jose]

> 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.

[Bill Zaleski]

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?

[.Blueskies.]

"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...

[Mike Granby]

> 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.

[Mike Granby]

> 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???

[Mike Granby]

>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?

[RST Engineering]

"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?

[jmk]

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.

[Newps]

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

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

[Michael]

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

No, by definiton.

An STC is issued as approved data for a MAJOR modification to the type
design.

A minor modification does not require approved data, it only requires
acceptable data.

However, what constitutes a major vs. a minor alteration is open to
interpretation, and to the extent official guidance exists (not often)
it has been known to change over time. For example, once upon a time
any RNAV installation was considered to be major. It required either
an STC or a field approval. If you look at the installation manual for
a KNS-80 VOR-DME RNAV, you will see included an STC for its
installation into a PA-30. The guidance on this has changed. These
days, the installation of a KNS-80 is generally treated as a minor
modification, but when it was new the FAA wanted to maintain control.
IFR GPS installation is going through the same process. Originally, an
STC or field approval was required, but the FAA has issued guidance
that certain simple IFR GPS installations (ones where there is no GPSS,
for example) may be treated as minor.

So there are STC's out there for the installation of a given piece of
equipment into a difference aircraft that are being cited as acceptable
data for a modification that used to be considered major but is now
well enough understood that it is considered minor.

If you're looking for hard and fast answers in this area, realize that
they are not to be found. What is major or minor varies from FSDO to
FSDO, and from year to year in a given FSDO. What will be considered
approved data also varies. I've had a 337 for a Stormscope
installation IAW an FAA APPROVED installation manual (comepte with
revision history) accepted one year, and an almost identical one
rejected a couple of years later. Policy had changed. You will NOT
get clear and unambiguous guidance on this from the FSDO. If you
insist on it, you will be told that everything is major and no field
approvals are available, so either get an STC or hire a DER. Or you
can live with a grey area.

Michael

[George Patterson]

RST Engineering wrote:

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

Jay's strobes were in the plane when he bought it. Fat lot of good that did him.

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.

[Montblack]

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

"George Patterson"
> Jay's strobes were in the plane when he bought it. Fat lot of good that
> did him.


Was that a case of not being able to get past the mechanic? I don't recall
the details.


Montblack

[George Patterson]

Montblack wrote:

> Was that a case of not being able to get past the mechanic? I don't
> recall the details.

Well, Jay will correct me, I'm sure, but the gist of it was that the FSDO told
him that the strobes that had been on the plane for a couple decades weren't
STCd and had to come off. Cost him a few grand.

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.

[Mike Granby]

To be fair to him, what he meant was that if you had a product that was
PMA/STCed for a given airframe (for example the B&C standby alternator
referened at [1] below) then the installation of this product did not
require a 337, even thought it was being installed using an STC. He
says that the PMA approval removes the need for additional paperwork.
My view is that you still need the 337 if it's a major alteration,
which this would be, and that the PMA-ness of the parts is merely
something that allows the manufacturer to put them on the market,

[1] http://www.bandcspecialty.com/PA32desc.html