One judgment, and forty elements of navigation

Forty-six elements. Read as a list it is the dullest subject in General and the one candidates least retain.

It is not a list. Six elements carry one judgment, and the other forty are navigation in service of it.

Learn those six and the rest becomes obvious. Learn the rest first and the six never arrive.

1. Major or minor decides what happens next

The determination is not academic. It decides whether you need approved data and whether you must file a Form 337.

• Minor — do the work to acceptable data, make a maintenance record entry under § 43.9, return to service. Done.
• Major — you need approved data, and the work is recorded on a Form 337 as well as in the maintenance record.

Get it wrong in one direction and an aircraft flies with an undocumented major alteration. Get it wrong in the other and you have filed paperwork nobody needed and possibly claimed approval you did not have.

Part 43 appendix A is a list, not an algorithm. It names things that are major, and it will not name the case in front of you. What the definitions actually turn on is effect: does this appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics or other qualities affecting airworthiness — and could it be done by elementary operations?

So the question to ask is not "is it on the list?" but "what does this change?" A candidate who reasons from effect can handle a case the list omits. One who reasons from the list cannot.

2. Two limitations on your certificate that surprise people

§ 65.81(a) is quoted in GEN-I Quick reference. Two parts of it are worth reading twice.

Propellers and instruments are carved out. An A&P may not perform major repairs or major alterations to propellers, and may not repair or alter instruments at all. Those go to appropriately rated repair stations. This surprises candidates who assume the certificate covers everything they can reach.

You may not approve for return to service work you have not satisfactorily performed before. Not "work you feel confident about" — work you have actually done, at an earlier date. If you have not, the regulation gives you the route: do it under the supervision of someone who has, or demonstrate it to the Administrator.

That is a legal requirement, and it is also the honest answer to the anxiety of a newly certificated mechanic. You are not expected to have done everything. You are expected not to sign for things you have never done, and there is a defined way to fix that.

K2 and § 65.83 add the other clock: the privileges lapse without recent experience in the preceding 24 months.

3. Approved against acceptable is about who approved it, not how good it is

Candidates reliably read "approved data" as better data. It is not a quality distinction.

Acceptable data is data the Administrator finds acceptable — the manufacturer's maintenance manual, AC 43.13 for practices where nothing more specific applies. Sufficient for minor work.

An advisory circular (AC) is guidance, not a rule. FAA-H-8083-30B Ch. 2, Advisory Circulars (AC), says an AC gives "methods, procedures, and practices acceptable to the Administrator for complying with regulations", and that ACs "do not create or change a regulatory requirement." Three things follow:

• It shows one acceptable method, not the only one. Another method may satisfy the same regulation.
• It is not binding of itself. In the handbook's words: "Unless incorporated into a regulation by reference, the content of ACs are not binding on the public."
• Its number tells you its subject. ACs are numbered to match the subject areas of 14 CFR, so AC 43.13 sits beside part 43.

Approved data is data the Administrator, or someone with delegated authority, has approved — type certificate data, an STC, an approved manual section, a field approval, a DER approval. Required for major repairs and alterations.

The same physical procedure can be either, depending on the document it came from and what that document was approved for. A manufacturer's repair may be approved data for the aircraft it was written for and nothing at all for a different model.

S17 asks you to explain the difference, not to recognize it, precisely because explaining it exposes whether the distinction is understood or recited.

4. A part that fits is not a part that applies

K21 usable-on codes, K22 serial number effectivity, R5 component applicability, S13 approved replacement parts, S9 TSO and PMA.

This is the third time this curriculum makes the same point in three different places — GEN-B Concepts §1 says it about drawings, GEN-E §5 says it about hardware in your hand, and here it is about part numbers.

An illustrated parts catalog lists parts against effectivity codes, and the code is the answer to "does this apply to my aircraft". A part number that appears in the catalog for a different serial range is a part for a different airplane that happens to share a book.

S9 adds the other question: a TSO or PMA marking tells you the part was produced under an approval, not that it is approved for your aircraft. Those are different claims and the distinction is exactly R5.

5. R3 is the element that should change how you work

Complacency during the documentation phase of maintenance procedures.

The ACS classifies documentation complacency as a risk, and the reason is timing. The paperwork is done last — when the work is finished, the aircraft is nearly ready, someone is waiting, and your attention has already moved on.

Every other unit's tasks end here, at the moment you are least inclined to be careful. That is not a character flaw; it is a predictable human factor, and GEN-L Concepts §4 explains the mechanism.

The countermeasure is structural, not motivational. Make the entry part of the task rather than after it:

• Write down what you did while you are doing it, not from memory afterwards.
• Record the data reference at the moment you use it, not when you try to recall which revision you worked from.
• Treat an incomplete entry the way you would treat an untorqued fastener — as work in progress that must not look finished (GEN-L Procedures Procedure 2).

R1, completeness and accuracy of documentation, is the same idea stated as an outcome.

6. What a maintenance record is actually for

Not compliance theater. It is the next mechanic's only source of truth about what was done to this aircraft, and you will be the next mechanic on somebody else's entry more often than you are the author of your own.

§ 43.9's four items make sense in that light: what was done, when, by whom, and who approved it. A description that says "serviced landing gear" satisfies nobody: it does not say which gear, what was serviced, to what data, or what was found.

K3 and K4 distinguish the entry after maintenance from the entry after inspection, and they are different because the claims are different. Maintenance says I did this work and it is airworthy for the work done. Inspection says I looked at this aircraft against a defined scope and here is its condition — which is why an inspection entry names the scope and states whether the aircraft was found airworthy.

7. Warnings, cautions and notes are a ranked vocabulary

K18 and R4 look like reading comprehension and are not.

The convention is consistent across manufacturers: a warning means personal injury or death; a caution means damage to equipment; a note means information that makes the task easier or clearer.

The same three words carry the same ranking in operating manuals — the airplane flight manual and the pilot's operating handbook — not only in maintenance manuals. The ACS element says so itself: it asks for warnings, cautions and notes "used in maintenance and operating manuals."

None of the FAA handbooks held here defines the three words. The definitions above are the convention manufacturers use, stated in our words, not an FAA definition. The manual in front of you governs: if it defines them, its definitions apply.

They are ranked by consequence, and skipping them inverts the ranking — because the ones easiest to skip are the ones printed most often. R4 exists because adherence degrades with familiarity, which is GEN-L Concepts §3's violation rather than error: a choice, not a slip.

8. What consumes this unit

This unit is the one every other unit ends in. That is why it is taught early and revisited, rather than taught once and finished.

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