Minor or major That is the question!

[minton]

My last face to face with the Feds was contact with my PMI concerning installation of rear bubble windows vs flat. Minor or major? Field approval or not?? His take on it was Minor modification. He required a written request for determination. In return I received a letter of determination from him. That coupled with your A&P log book sign off and you're good to go.

I feel this is a good approach for a couple of reasons.

1) It gets the facts put in writing such as installation techniques, reference to AC 43.13 and /or MFG maintenance manuals, materials used in installation, any airworthiness issues and methods, materials of manufacture.
2) It gets you a legal document that holds water down the road.
3) Provides an extra copy for your mechanics files for the next time.
4) Eliminates some confusion as to who can make that determination. In the past, well it was sometimes left to ??

Hope this helps someone down the road.

[Bruce Fenstermacher]

Yes I recently read AC 43- 210 were it talked about being issued a letter of determination when an approval, other than a log entery, was not needed. I thought, what a novel idea.

[hilltop170]

Minton-
I never heard of that before but could have sure used one a time or two. Sounds like a good idea and holds the fed's feet to the fire should the decision ever be questioned down the road. Thanks for sharing.

Case in point:
The Horizon P-1000 digital electronic tach has been STC approved for many airplanes listed on the Approved Model List (AML).
The C-172A with an O-300-D engine is on the AML.
No C-170 with an O-300-D engine is on the AML although the installation is essentially the same and the engine is exactly the same as the C-172A.
The local FSDO inspector said go ahead and install it with a 337 and log book entry, no field approval required.
The next annual, a different IA says the tach is illegal because it was not field approved and will not sign off the annual.
Since no written record exisits of the original FSDO Inspector's determination, the annual is not completed until I go back to the original FSDO Inspector in another state and ask him to go ahead and sign off a field approval, which he begrudgingly does.
A letter of determination would have eliminated all the unnecessary BS, frustration, and anxiety.

By the way, I like the digital tach very much. It works very well with the vernier throttle.

[lowNslow]

The local FSDO inspector said go ahead and install it with a 337 and log book entry, no field approval required.

This is the problem when certain FSDOs require 337s for MINOR alterations. A 337 is for either a MAJOR repair or MAJOR alteration. A major repair can be signed off by an IA with supporting info, a major alteration needs either a change to Type Cert., an STC, or a field approval from the FAA for a return to service. I think the procedure minton mentions gets around this problem. Some regions also suggest submitting an UNSIGNED 337 for the same purpose which does not create an open 337 on your aircraft.

[minton]

Karl,

You migh be right. I have only been required to submit unsigned 337 with a AC 210 submission, But, the feds seem to go the direction they choose even though they have a very thick "guidance manual" It used to be the "8800". Think is has changed.

The best suggestion I have for the "Instrument Panel Electrification" Folks is give this system a try.

That letter is golden!!

[n2582d]

Cessna video on the subject of major vs. minor repair/alteration.

[minton]

Having just viewed the "Cessna" video they have brought to light some of the issues you would come up against with this issue. The ones that most impact major/minor that cause me grief are the outdated part 43 and FISDO interpretations even with the guidance manual in hand. It really helps to have an AI with a good PMI in his corner and the pair in yours.
Also the Approved Data issue causes problems on a daily basis. I hope that someday some real guidance will be in place although being 66 yo maybe not