FAA-PMA, STC, and TSO...

S

Swede

New member
These are becoming some of my most hated acronyms! I am rebuilding my 7ECA, which had some decrepit instruments. One by one, I've begun to replace or upgrade them. Let's look at oil pressure. I can go the Aircraft Spruce and buy a quote

"2-1/4 inch UMA Electronic Oil Pressure Gauge TSO'd Range 0-100 PSI"
or
"Westach Instruments has FAA approval on all the instruments listed below. These gauges are fully approved for installation in factory aircraft..."

I'm guessing I can buy one of these and install it legally. Yet when I look at other items, such as a Horizon tachometer, or a spin-on oil filter adaptor, the device requires an STC for the specific make and model of aircraft. Can someone using plain English, explain what all this means? I would be very appreciative, and it would help me get my Citabria flying that much sooner.
 
Hi Swede, FAA-PMA means the maker of an item/product has FAA approval to make these items and has approval data to back it up, these parts are like spark plugs, magnetos, starters, oil filters etc these can be installed by an A&P and signed off by an A&P, TSO items like radios, instruments, seat belts etc are like that also. STC items are generally a modification to the airframe or engine and the STC holder has gotten all of the approval data approved but requires a FAA form 337 and an A&P plus an IA to sign the form 337 ( the IA can also be the A&P or and A&P can take the paper work to an IA to have it signed).The local FAA office need not be involved as the part is approved and just needs to be recorded in the aircrafts permanent records at OK City.
 
PMA means the part can used as a specific direct replacement. PMA'd for Cub doesn't mean you can use it on a champ, for example. PMA's are weird in that they can be for a specific part that is on all planes or just a plane.

TSO means the part has met the generic all encompassing requirements for use in pretty much any aircraft. However, it does not mean that they can be used in a specific aircraft without approval. Sounds funny, but, lets make something up and say the Garmin 970DXQ makes a certain magnetic field that throws off the compass unless you move the compass. Seems to affect the Citabrias, but its fine in a Cherokee 140. Its a made up example, but its one reason, TSO is not a direct replacement. TSO does not have specific installation instructions either. For example, the EDM 930 is a TSO'd unit, but you need an STC (or TC data, in our case) to install the unit because of the complexity. Now flip side, a TSO'd piece of equipment is much much easier to get approved. In the case of basic flight instruments, I can't see why a 337 would not cover it.

In the case of the UMA gauge, what you want is:
It to be TSO'd to show it met the minimum requirements, and you want it PMA'd to be used on a 7ECA or to replace any installation of an approved guage (I would expect the latter). Now if there is a PMA for a specific part it doesn't mean the item needs a TSO. Its likely the TSO helped get the PMA though.

Is that clear as mud?

TSO means good unit, has nothing to do with usable.
PMA means you can use the unit, good or bad.
So, you want both, if posible.
 
Thank you, guys. When I say "I am installing..." it really means "We" as in my A&P buddy, and I. He is letting me turn some wrenches with oversight and overall approval, but he seems to be as confused as me in a few cases.

I like the way Wag Aero lists their hardware. They "Code" it, codes 1 through 9, each meaning something different as far as the suitability. Their "code 4" items are listed like so:

Code 4; These items are FAA/PMA'd, TSO'd and/or STC'd or are produced under a TC; or are overhauls by an FAA certified repair facility. The holder of the Approval may be either the Wag-Aero Group or an outside vendor.
Click to expand...

Anyway, it's been quite a struggle, and it's annoying, too, when you see THE EXACT SAME GAUGE going for two different prices, with the "TSO'd/STC'd" variety being double or triple the cost.
 
Jerry's post is excellent but some further clarification might be helpful, any equipment installed must be FAA Approved for use in Certified aircraft, unless it is approved under the manufacturers Type/Production Certificates. The most basic level of approval is FAA-PMA, if a direct replacement a logbook entry will usually suffice, if an addition or modification a 337 will be required as a minimum. If the item is not listed in the TCDS then an STC will be required.

TSO means that in addition to being FAA Approved the appliance meets a specific Technical Standard Order that it will perform to specified standard, accuracy, etc. TSO'd equipment is required in Transport Category aircraft, in Part 135 operated aircraft, BUT not in Part 23 aircraft except in certain circumstances such as IFR certified GPS navigators because IFR GPS Approval is based upon meeting the TSO standards.

As an example in a Part 23 aircraft, operated under Part 91, you can replace the altimeter with a like altimeter that is FAA-PMA you would not need to use a TSO'd altimeter unless the installation was in a Transport Category aircraft or one used in Part 135 operations. Another example would be equipping a Citabria for IFR GPS ops, either enroute or approach, in which case the only IFR Approved GPS navigators must be TSo'd

Tom-
 
For further mud on the wind shield, if you want to put a non-TSO'd, non-PMA'd unit in a part 23 airplane, then prior to installation you will have to show the item meets the TSO or at least any items in the TSO that could affect the airplane. Its not the writen rule, but its the policy. Basically TSO specs are considered a 'minimum' standard. Makes a lot of sense to me....not! If its the policy, the FAA should just require TSO for everything. Meh, I rant.
 
jerrymjr said:
For further mud on the wind shield, if you want to put a non-TSO'd, non-PMA'd unit in a part 23 airplane, then prior to installation you will have to show the item meets the TSO or at least any items in the TSO that could affect the airplane. Its not the writen rule, but its the policy. Basically TSO specs are considered a 'minimum' standard. Makes a lot of sense to me....not! If its the policy, the FAA should just require TSO for everything. Meh, I rant.
Click to expand...

Yes, and no, actually PMA is the minimum standard, for many items/appliances no TSO exists and Part 23 VFR aircraft have been built and operated safely with FAA-PMA'd but not TSO equipment forever. Attempting to install and get approval for the installation of non-PMA'd equipment, even if the equipment is not required, is essentially impossible today. Personally I agree 100% with you, given a choice between PMA'd and TSO'd I will always choose TSO'd but I made the distinction between PMA and TSO because I've often seen pilots buy a twice as expensive TSO'd altimeter for their Day/VFR Cub because of a misunderstanding between the two standards and when TSO was required. Just as we've often seen the non-PMA'd, non-TSO'd, non-STC'd, installations that could cause an unsuspecting IA to loose his livelihood if he Annua;s the aircraft.

Tom-
 
Tom, that is interesting. Given that premise, let me give an example. UMA makes a LOT of instruments of all sorts, airspeed, oil gauges, etc. Many of them are TSO's and good to go for certified aircraft. So we know that UMA a FAA-PMA manufacturer. They make good, aircraft-quality stuff. Can I install a UMA gauge that is not TSO'd into my Citabria?

The 337 thing has me confused. It doesn't seem to me that replacing an oil pressure gauge is any sort of a major alteration or repair. Given the above scenario, when is a 337 REQUIRED? My brain hurts. :?

Every single gauge on my 7ECA except the airspeed and tachometer was in terrible shape, and I need to replace it all. Thanks for everyone's help.
 
Swede-

The UMA website shows that all but one of their FAA Approved instruments are TSO'd, the one exception being the Gyro Suction Gauge which is FAA-PMA but not TSO. I suspect the except is because there is no TSO for that instrument.

Tom-
 
Swede said:
Tom, that is interesting. Given that premise, let me give an example. UMA makes a LOT of instruments of all sorts, airspeed, oil gauges, etc. Many of them are TSO's and good to go for certified aircraft. So we know that UMA a FAA-PMA manufacturer. They make good, aircraft-quality stuff. Can I install a UMA gauge that is not TSO'd into my Citabria?

The 337 thing has me confused. It doesn't seem to me that replacing an oil pressure gauge is any sort of a major alteration or repair. Given the above scenario, when is a 337 REQUIRED? My brain hurts. :?

Every single gauge on my 7ECA except the airspeed and tachometer was in terrible shape, and I need to replace it all. Thanks for everyone's help.
Click to expand...

TSO's don't apply to specific aircraft.
PMA does (or can apply to a specific item instead). In your specific senario, PMA is the gold nugget for you.

Therefore, you need to find:
1) What UMA's PMA applies to. If its open ended, you can probably swap things out easy.
2) If there is no coverage via PMA, then a 337 for a TSO'd instrument.

OR:

3) United Instruments 8025 or Sigmatek EA5171-2-AC are TC approved. (The Sigmatek number is specific to the 7ECA/7GCAA).
I guess I am suprised there is no UMA in the spec. (yet) I see a UMA VSI, Vacuum Gauge, and Manifold Pressure

As for PMA being the minimun standards, well, PMA is not a standard. When there is no TSO for the respective item, you are down to the FAR's as standards.
 
We seem to be having a somewhat confusing discussion over the semantics of the word "standard", while there is no doubt that TSO is a Technical Standard Order the minimum "standard" for installation/use in a certified aircraft remains FAA-PMA approval and inclusion on either the original Type Certificate or a Supplemental Type Certificate.

The FAA clearly states that PMA is a "combined design and production approval for modification and replacement parts", a minmimum for use on certified aircraft.
http://www.faa.gov/aircraft/air_cert/design_approvals/pma/
From this site you can link to further information on PMA design/production approvals.

The TSO process means that a particular part or appliance meets a "minimum performance standard", while not clearly stated this is a higher standard than PMA, it is important to understand that TSO's do not exist (or are required) for all parts or appliances installed on certified aircraft BUT all parts or appliances must be PMA'd. It is also important to understand that for light aircraft TSO is not a hard requirement for example a non-TSO'd moving map may be installed for VFR use if PMA'd but for IFR use a TSO'd GPS is required to guarantee minmimum performance.
http://www.faa.gov/aircraft/air_cert/design_approvals/tso/
Even FAA inspectors are often confused about when a TSO'd item is required, large Transport Category (Part 25) aircraft are required to use TSO'd parts, commercialy operated aircraft (Part 121, 135) are required to used TSO'd items, for example a headset used in a Part 25 aircraft, or one operated under Part 121/135, must be TSO'd.

Anything not included in the original Type Certificate must be approved under a Supplemental Type Certificate (or a Field Approval), any major repair or modification (including something installed under a STC) must be documented on a FAA Form 337 submitted to the FAA and retained in the aircraft records (AFM). While Field Approvals are now usually difficult to obtain they are frequently used for simple avionics installations.

Tom-
 
Tom said:
The FAA clearly states that PMA is a "combined design and production approval for modification and replacement parts", a minmimum for use on certified aircraft.
Click to expand...

So, you are saying I am wrong and then you quote this?
PMA is an APPROVAL not a standard...RIGHT THERE. If there is no TSO then you get a PMA with FAR compliance...said this last post.

Whatever, you win, I am done with this discussion.
Since I do (or did) this crap for a living, maybe I better get a new job; so I dont starve the kids.
 
Jerry-

Clearly I was using the term "standard" as it is defined by Webster, not as it is used in TSO, to clarify that a PMA'd product is the minimum requirement (standard) for installation is a FAA Standard Category aircraft and that point was clearly made in my posts.

I never questioned your knowledge or expertise BUT was attempting to simplify our responses to the original post because this is a subject of much apparent confusion within the community. The links were provided for the edification of the group not to prove you wrong or me right.

Tom-
 
I can fix this problem. I have installed ACA (Mitchell) engine instruments in my 7ECA last year and had no problem with any paperwork as they are what ACA installs in new A/C. Now I want to replace them with ECI gauges which I believe are approved as the factory also uses them. If you want to buy my ACA (Mitchell) gauges you can.

Jeff
 
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