TSO, PMA, STC, 337, Field Approval, and Such

weirdjim

weirdjim

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weirdjim
In another thread, we've been throwing around these terms pretty loosely, and it might be wise to talk about them a bit to see if we can come to some understanding as to what they really mean.

I'll start it off with some simple definitions without any exposition as to meaning (corrections appreciated):

TSO -- Technical Standard Order. A written document as to requirements for a particular piece of equipment without reference as to what particular aircraft on which it is going to be installled. It will generally (but not always) reference an industry standard document for the technical specifications.

PMA -- Parts Manufacturing Approval. A letter of permission from the FAA to produce a specific part or series of parts in accordance with specific documents, components, and/or processes.

STC -- Supplemental Type Certificate. A letter of permission from the FAA for a particular part or parts to be installed on a particular airframe(s) or engine(s) in accordance with a specific set of instructions. (An exception to this general rule is the EAA/Petersen Auto Gas STC which allows an industry standard fuel to be used on a particular airframe(s) with specific engine(s).)

337 -- FAA form number 337, MAJOR REPAIR & ALTERATION (Airframe, Powerplant, Propeller, or Appliance). A misnomer for sure, because taken grammatically literally you would have to do a repair AND an alteration at the same time, which is just not the way it is done.

Field Approval -- An FAA countersignature to the A&P IA's signature on the 337 that constitutes "acceptable data" for the completion of the form.
​
I'm sure this sucker will generate more than its share of "internet lawyers" that may or may not have their basis in regulation or fact, but what the hell, let's get the discussion going.

Jim
 
Your definitions are great- where we stumble is understanding the practical use of each. When they are needed, esp.
 
Let'sgoflying! said:
Your definitions are great- where we stumble is understanding the practical use of each. When they are needed, esp.
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I agree, and I hope by the end of this thread we will have the chance to thrash that out. It might have been wise to create 5 separate threads and thrash out each one separately, otherwise we will wind up in the proverbial internet merry-go-round. What say all?

Jim
 
AFMS, ICA, MDL, ODA, 8130-3, C of C, 8100-11, 8100-9, 8110-3

I'd bet most IAs don't know these.
 
weirdjim said:
337 -- FAA form number 337, MAJOR REPAIR & ALTERATION (Airframe, Powerplant, Propeller, or Appliance). A misnomer for sure, because taken grammatically literally you would have to do a repair AND an alteration at the same time, which is just not the way it is done.

Field Approval -- An FAA countersignature to the A&P IA's signature on the 337 that constitutes "acceptable data" for the completion of the form.​
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​
https://www.faa.gov/documentLibrary/media/Form/Form_337.pdf

337 being dual purpose confuses many

Stamp by FAA in block 3 indicates that unapproved data listed in block 8 is FAA approved otherwise known as a "Field Approval". Block 3 only approves design data and not physical aspects like workmanship quality and final product.

Only FAA approved data (see STC, 8100-9, 8110-3, 8100-11 and others) should be used in block 8 unless a "Field Approval" is being sought. If using approved data in block 8, block 3 is not needed.

Many assume that any OEM or vendor publication is FAA approved and it very well may not be. "FAA approved" is the most abused term in all of aviation.
 
being a car 3 cert aircraft a lot that stuff goes out the window correct?
 
car 3 cert aircraft, vs pt 21 approved, is a whole world apart. I always thought you, weirdo. were a fraud , troll, even with all the certs you say you have this thread proves it .and is entertainment YOU started for your arguemenitive pleasure .you are on my ignore list and this thread is dilldooos . I have been watching you for a long time and are totally sure of my belief.glad you live in ca. priceless! eta you called me ignorant so I guess I wont be band for defending myself .
 
Ignoring the vitriol, it is pretty clear; every answer is "depends". A CAR 3 airplane isn't the equivalent of experimental armature built, they are treated the same as a Part 23 airplane in most aspects. In fact, during the creation of the certification plan on a CAR 3 STC project the FAA can determine at-will whether or not CAR 3 is adequate or will Part 23 be applied. If Part 23 is inadequate then that is Special Conditions and Equivalent Level of Safety territory.

Every office is different. Every individual's comfort level is different.
 
Jim is right in his definitions, but of course, it skirts the issue as to what those implications mean to a pilot.
I should point out that the TSO is just the standard. There's also a TSOA which includes a determination of compliance with the TSO and in most cases authority to manufacture the part.

Generally, there are THREE things you need to have to put a part on an aircraft:

1. First, the part must be a legal aircraft part. There are many ways to have a legal part. It can be done under the manufacturer's production authority for the type certificate of the aircraft, engine, or propeller. It can be produced under a PMA or TSOA. Some parts are allowed to meet other standards (such as MIL-SPEC for things like nuts and bolts). Then there's one catch all. An owner under certain circumstances can produce his own parts (to a reasonable standard) for his own aircraft.

2. Second, the part must be legally installable on your aircraft. Just because an IO-720 has a TC and legally produced doesn't mean I can go hang it on my Piper Cub. There are a number of ways that this can be done:
a. It can be in compliance with the TC of the aircraft. Generally, everything that was already there, you can replace. In addition, the TC may provide for "optional" or "alternate" equipment. For example. You can hang big engines (up to an IO-520) on the Navion following the TC notes.
b. Another way to get approval is for a manufacturer to get a STC.
c. Another way is to determine that the change is not a "major modification or alteration" under the rules and that you're doing this with accepted maintenance practice.
d. The final way, is the catch all "other data acceptable to the administrator." This comprises things like "one off STCs" and "field approvals." Alas, the FAA really wants to move away from these. They've made it harder for bigger things (like engine swaps). The FAA really wants to wipe out the entire field office system. Expect that to happen.

3. You have to complete the required maintenance paperwork. If it is a major modification, then you must file a 337. A 337 is still submitted with STCs. It also, as Jim mentions, can be used when submitting other data (field approvals or what not). You IA signs the 337 and the FAA accepts it and you're good. Of course, you must make the entry into the aircraft maintenance records (as well). Note that, if the TC provides for something, it's not a "major modification." It still needs the maintenance records. This is why I could have hung an IO-520 on my Navion with just a sign off in the log book (though since I made other modifications like the engine mount change, I used the STC route).
 
Oh, c'mon, hotprops. We are all ignorant of some things. I'm ignorant of brain surgery. I'm ignorant of C++ coding. I'm even ignorant of some of the stuff in this thread. That's why I started it. Lighten up and learn. That's what we are all here for.

Jim
 
weirdjim said:
Oh, c'mon, hotprops. We are all ignorant of some things. I'm ignorant of brain surgery. I'm ignorant of C++ coding. I'm even ignorant of some of the stuff in this thread. That's why I started it. Lighten up and learn. That's what we are all here for.

Jim
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and you my friend......are very humble too. o_O
 
Okay, I've purchase TSO'd equipment from a TSOA manufacturer and it came with an STC and a 337 was filed. Hmmm, haven't worked in PMA or a field approval but a previous owner did get a field approval for installation based on an STC for a similar airframe.

The aircraft does have PMA parts and A&P produced parts. And the hangar fairies have done a little work from time to time...mostly just fiberglass...
 
I think most folks confuse design approvals with installation approvals.
 
hotprops said:
car 3 cert aircraft, vs pt 21 approved, is a whole world apart. I always thought you, weirdo. were a fraud , troll, even with all the certs you say you have this thread proves it .and is entertainment YOU started for your arguemenitive pleasure .you are on my ignore list and this thread is dilldooos . I have been watching you for a long time and are totally sure of my belief.glad you live in ca. priceless! eta you called me ignorant so I guess I wont be band for defending myself .
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Do you know the difference between ignorance and stupidity?

For example, because you seem to be ignorant of the proper location of a period in a sentence of knowing when to capitalize letters does not mean you are stupid.

But we can hope you will be "band".
 
^^^ that guy is being mean to the other guy who can't write good like us can and I don't know if is that a'ight.
 
pasta man funny as always.jim you need to study up on car3 ,
 
Do we want to get into major and minor alterations? I believe that it would neatly fall into the "and such" bin of the OP. I've said it before and I'll say it again. Aviation regs are like the bible and different people interpret them in different ways. For example, I had an IA tell me that changing my air filter on my Piper Cherokee from the Brackett snot-filled foam filter to a paper filter would be a major alteration. I can't see why that would be the case.
 
hotprops said:
pasta man funny as always.jim you need to study up on car3 ,
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Funny you should mention CAR-3 ("C3"). I decided to try and find out what happened when we went from C3 to 14CFR23 and there is a definite lack of information on that transition. And trying to find out what particular aircraft are certificated under C3 and which are 23 is nearly impossible.

Let me give you an example. I've got a 1958 C-182A. Nowhere in the Type Certificate Data Sheet (TCDS) does it mention which of these two sections this particular airplane rolled out of Wichita with. Cessna website is worthless. Old wives' tales abound. But hard data is damn near impossible to come by. Anybody got a point?

Just FYI, even the Feds have written a report stating that aircraft built to C3 are sturdier than those built to 23. That's interesting. I also found out why 12,500 is the split between "little" and "big" aircraft. More on that later.

Jim
 
weirdjim said:
Funny you should mention CAR-3 ("C3"). I decided to try and find out what happened when we went from C3 to 14CFR23 and there is a definite lack of information on that transition. And trying to find out what particular aircraft are certificated under C3 and which are 23 is nearly impossible.

Let me give you an example. I've got a 1958 C-182A. Nowhere in the Type Certificate Data Sheet (TCDS) does it mention which of these two sections this particular airplane rolled out of Wichita with. Cessna website is worthless. Old wives' tales abound. But hard data is damn near impossible to come by. Anybody got a point?

Just FYI, even the Feds have written a report stating that aircraft built to C3 are sturdier than those built to 23. That's interesting. I also found out why 12,500 is the split between "little" and "big" aircraft. More on that later.

Jim
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It actually does say on the TCDS. Every TCDS I've ever seen calls out the "Certification Basis" of the particular make/mode. For the 182, take a look at Page 20 of the TCDS.

It says, in pertinent part,
"Certification Basis:
182 Series
Part 3 of the Civil Air Regulations..."

http://rgl.faa.gov/Regulatory_and_G...6210c7286257ebd006029c5/$FILE/3A13_Rev_72.pdf
 
weirdjim said:
Funny you should mention CAR-3 ("C3"). I decided to try and find out what happened when we went from C3 to 14CFR23 and there is a definite lack of information on that transition. And trying to find out what particular aircraft are certificated under C3 and which are 23 is nearly impossible.

Let me give you an example. I've got a 1958 C-182A. Nowhere in the Type Certificate Data Sheet (TCDS) does it mention which of these two sections this particular airplane rolled out of Wichita with. Cessna website is worthless. Old wives' tales abound. But hard data is damn near impossible to come by. Anybody got a point?


Jim
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And you hold an IA.

Amazing.
 
Jim12,500 ft because 13000 or the number 13 was thought to be bad luck.
now lets talk Cessna ,American champion,Mooney if they were built in the 1940s or 50s they were car3. case in fact the c172 was car3 up to p model, now this is important, all "follow on aircraft" had specific updates added by number in order and are annotated on the tcds for that specific aircraft and ser# a real cumbersome way of doing things.so along comes part 23.fyi American champion is STILL car3 with all the cumbersome add-ons on all the 7 series. same text up to item 13 or there about as my 1946 7ac champ . more to follow.
 
hotprops said:
Jim12,500 ft because 13000 or the number 13 was thought to be bad luck.
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Doubtful. 12.5 for oxygen issues is based on where the p02 cross a couple of major numerical limits.
 
hotprops said:
Jim12,500 ft because 13000 or the number 13 was thought to be bad luck.
now lets talk Cessna ,American champion,Mooney if they were built in the 1940s or 50s they were car3. case in fact the c172 was car3 up to p model, now this is important, all "follow on aircraft" had specific updates added by number in order and are annotated on the tcds for that specific aircraft and ser# a real cumbersome way of doing things.so along comes part 23.fyi American champion is STILL car3 with all the cumbersome add-ons on all the 7 series. same text up to item 13 or there about as my 1946 7ac champ . more to follow.
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The G36 Bonanza is still primarily certified under CAR3, with some additional certifications done under Part 23 for the G1000.
 
weirdjim said:
Funny you should mention CAR-3 ("C3"). I decided to try and find out what happened when we went from C3 to 14CFR23 and there is a definite lack of information on that transition. And trying to find out what particular aircraft are certificated under C3 and which are 23 is nearly impossible.

Let me give you an example. I've got a 1958 C-182A. Nowhere in the Type Certificate Data Sheet (TCDS) does it mention which of these two sections this particular airplane rolled out of Wichita with. Cessna website is worthless. Old wives' tales abound. But hard data is damn near impossible to come by. Anybody got a point?

Jim
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There is no magic here, ASIs, DERs, DARs, ODAs, IAs, DOAs, ACOs, A&Ps all use TCDS to find certification basis. Interesting you didn't know where to find it.
 
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Timbeck2 said:
Do we want to get into major and minor alterations? I believe that it would neatly fall into the "and such" bin of the OP. I've said it before and I'll say it again. Aviation regs are like the bible and different people interpret them in different ways. For example, I had an IA tell me that changing my air filter on my Piper Cherokee from the Brackett snot-filled foam filter to a paper filter would be a major alteration. I can't see why that would be the case.
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The following link might help clear things. A change in the air filter media can have serious consequences.
https://www.aea.net/governmentaffairs/pdf/ViewSept06.pdf
 
Clark1961 said:
but a previous owner did get a field approval for installation based on an STC for a similar airframe.
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When you do that, it is called " asking for a deviation to an STC"

You simply show the STC was for X-a aircraft. but will work just as good on X-b aircraft.
 
bradg33 said:
The G36 Bonanza is still primarily certified under CAR3, with some additional certifications done under Part 23 for the G1000.
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So tell me what the difference is in requesting a modification on a 337? or show me the difference in the form.
 
weirdjim said:
Field Approval -- An FAA countersignature to the A&P IA's signature on the 337 that constitutes "acceptable data" for the completion of the form.
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Not really, when you request a field approval you follow AC 43-120 with a cover letter, and a completed 337 with the modification in block 8.
When the ASI/PMI signed the 337 in block 4 that 337 becomes approved data to do the modification on one aircraft that one in block 1 for the form.

All Field approvals are a pre approved prior to work beginning
 
Who can fill out a 337 request for approval of a major repair?
 
Tom-D said:
Who can fill out a 337 request for approval of a major repair?
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Ahhhh there's the ole Tom we know! Idk Tom you tell me! I don't know jack about this
 
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