Classification of minor & major repair 5

[Ruag]

Hi guys,
Can anybody help me to understand how can I classify a repair?
I mean, which variables do I have to consider to come to a major or minor repair for critical or not critical parts.
Is a repair on critical parts always a major repair?

I appreciate your feedback,
Cheers,
D.

 

[rb1957]

at an OEM i used to work at the distinction between major and minor repairs was major if DTA required special inspections; more frequent inspection, different method of inspection, basically a change to the approved inspection program. extensive repairs could be minor if no additional inspections were required.

 

[Ruag]

Thanks rb1957,
do you take into account if the part is classified critical (or not) for your evaluation?
(Definition of critical part: A critical part is a part, the failure of which could have a catastrophic effect upon the A/C, and for which critical characteristics have been identified which must be controlled to ensure the required level of integrity)

 

[thruthefence]

This is from 14 CFR part 1: ( I'm assuming a USA registered aircraft )

" Major repair means a repair:

(1) That, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or

(2) That is not done according to accepted practices or cannot be done by elementary operations."

Kinda vague, huh?

Note this phrase: might appreciably affect

It's up to you to PROVE by citing chapter & verse of the cert. regs that no-way-no-how is your repair going to "affect" the above mentioned areas, when seeking approval for the repair.

The following should clear everything up. Also from Part 1:

"Minor Repair. A repair other than a major repair."

Here are some advisory circulars dealing with the issue:

http://rgl.faa.gov/Regulatory_and_G...ircular.nsf/list/AC 43-210/$FILE/AC43-210.pdf

http://rgl.faa.gov/Regulatory_and_G...ular.nsf/list/AC 43.9-1F/$FILE/AC 43.9-1F.pdf

 

[rb1957]

i would deliberately consider the "criticality" of the part. one factory repair fixed a wing where the integral fuel tank had been over-pressurised by production (in fact they'd blown the wing apart); this was classified minor ('cause there was no change to the inspection program). installing an oversize fastener can be a major; fasteners installed with reduced edge distance can be major.

i think it (part criticality) would come into play when you consider the affect of your repair on the existing inspection program; eg if you cover the surface with a doubler, now you change the inspection technique from visual/HFEC to LFEC.

 

[chief52]

Transport Canada defines it like this:

http://www.tc.gc.ca/eng/civilaviation/regserv/cars/part5-standards-571s-1827.htm#571s_06

And they then provide a list of questions to help you decide if the repair or modification is major or minor:

http://www.tc.gc.ca/eng/civilaviation/regserv/cars/part5-standards-a571sa-1893.htm

Still leaves lots of room for interpretation! (Other than a negligible effect...)

 

[Metalsmythe1977]

I use an SRM for a military aircraft that classifies a major repair as: "A repair that involves restoring two or more primary structural members to original loadcarrying requirements
and/or aerodynamic characteristics is considered a major repair."

 

[dgapilot]

Thruthefence has it. 14CFR 1 covers it. It is the person doing the repair that makes the determination. 14CFR43 Appendix A also gives guidelines. An even better guide is in Order 8900.1 Volume 4 Chapter 9 where there is a flow chart for Field Approvals. All that said, the only real differences between major and minor repairs are 1. how it is recorded (337 for major, and log entry for minor), and 2. approved data for major and acceptable data for minor. It doesn't mean that the data has less rigor for a minor repair it's just that it doesn't have to be Approved, merly accepted.

As I said, the installer makes the determination. I've made a point to include my logic for determining minor in my log entries so anyone trying to second guess me can see how I made the determination.

Major and Minor have been argued for the 30+ years I've been in this business and FAA pendulum seems to swing back and forth. It's a moving target. If you really want to be sure, always use approved data, but that requires $$$ to get it approved.

 

[mfgenggear]

I was under the impression if it affected fit, form or function it was major?

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[berkshire]

As Dave says it is a moving target.
I have seen repairs that should have a form 337 filled out done with just a logbook entry, and a 3" tear in fabric that could have been done with a logbook entry, with a 337 form and an additional page attached.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[dgapilot]

If anyone wants, last year I did a presentation for an IA seminar on this very subject. Send me an email at n14ky@aol.com and I'll send you a copy of my powerpoint presentation.

David