Guide
AC 43.13-1B explained: what it is and isn't
What AC 43.13-1B is, when you can use it, why it is acceptable data and not approved data, and when it can be used for a major repair.
What is AC 43.13-1B?
AC 43.13-1B is an FAA advisory circular called "Acceptable Methods, Techniques, and Practices: Aircraft Inspection and Repair." It is a big book of standard ways to inspect and repair the parts of civil aircraft that are not pressurized. You use it when the manufacturer has no repair instructions for the job. [AC 43.13-1B, Par. 1, Purpose, p. 1]
Mechanics just call it "43.13." It covers wood, fabric, fiberglass, sheet metal, welding, inspection methods, corrosion, hardware and more. [AC 43.13-1B, Table of contents, p. 2 to 16]
When can you use AC 43.13-1B?
Only when there are no manufacturer repair or maintenance instructions for the job. The manufacturer's manual comes first. If it covers the repair, you follow it. The AC fills the gap when it doesn't. The data in it mostly covers minor repairs. [AC 43.13-1B, Par. 1, p. 1]
That order comes from the rule every mechanic works under. You must use the manufacturer's current maintenance manual or Instructions for Continued Airworthiness, "or other methods, techniques, and practices acceptable to the Administrator." [14 CFR Part 43, § 43.13(a)]
What is the difference between approved and acceptable data?
Approved data has been approved by the FAA for a specific job. Acceptable data is data the FAA accepts as a good way to do work. Acceptable data is fine for minor repairs. Major repairs and major alterations need approved data. AC 43.13-1B is acceptable data. [AC 43.13-1B, Par. 1, p. 1]
| Compare | Approved data | Acceptable data |
|---|---|---|
| What it is | Data the FAA has approved for a job | Methods the FAA accepts as good practice |
| Examples | Type certificate data, approved repair data | AC 43.13-1B, AC 43.13-2B |
| Use it for | Major repairs and major alterations | Minor repairs and minor alterations |
This exact difference is on the test. The ACS lists "Difference between approved data and acceptable data, and when each is required" as a General knowledge item. [FAA-S-ACS-1, AM.I.I.K16, p. 19]
Can AC 43.13-1B be used for a major repair?
Yes, but only under three conditions. The data can be used as approved data, and listed in block 8 of FAA Form 337, when it is right for the product, it applies directly to the repair, and it does not go against the manufacturer's data. If any one of those fails, you need other approved data. [AC 43.13-1B, Par. 1, p. 1]
Technical details: the purpose paragraph, word for wordShow
"This advisory circular (AC) contains methods, techniques, and practices acceptable to the Administrator for the inspection and repair of nonpressurized areas of civil aircraft, only when there are no manufacturer repair or maintenance instructions. This data generally pertains to minor repairs. The repairs identified in this AC may only be used as a basis for FAA approval for major repairs. The repair data may also be used as approved data, and the AC chapter, page, and paragraph listed in block 8 of FAA form 337 when: a. the user has determined that it is appropriate to the product being repaired; b. it is directly applicable to the repair being made; and c. it is not contrary to manufacturer's data." [AC 43.13-1B, Par. 1, p. 1]
What makes a repair major or minor?
A major repair is one that, done wrong, might noticeably affect weight, balance, strength, performance, engine operation, flight handling or other airworthiness qualities. A minor repair is any repair that is not major. Appendix A of Part 43 lists examples of major repairs. [14 CFR Part 1, § 1.1] [14 CFR Part 43, Appendix A]
Deciding major or minor is your job as the mechanic. It is also an ACS knowledge item.
Technical details: the definitionsShow
14 CFR § 1.1: "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." "Minor repair means a repair other than a major repair." Part 43, Appendix A, paragraph (b) lists airframe, powerplant, propeller and appliance major repairs. [14 CFR Part 1, § 1.1]
What is AC 43.13-1B not?
- Not a rule. It is guidance. The rule is § 43.13. The AC is one accepted way to meet it. [14 CFR Part 43, § 43.13(a)]
- Not first in line. If the manufacturer has instructions, those come first. [AC 43.13-1B, Par. 1, p. 1]
- Not for pressurized areas. Its purpose covers nonpressurized areas only. [AC 43.13-1B, Par. 1, p. 1]
- Not for alterations. Alterations are in its sister book, AC 43.13-2B. [AC 43.13-2B, Purpose, p. 1]
- Not automatic approved data. It counts as approved data only under the three conditions above.
Why does this matter for the A&P tests?
Approved versus acceptable data is a General knowledge item on the written. And in 2026 the FAA rebuilt the practical test questions to line up with aircraft maintenance manuals and advisory circulars. That change is to the practical test only, not the written. On the practical, you will be finding answers in real data, not reciting them. [FAA-S-ACS-1, AM.I.I.K15, K16, p. 19] [ATCA-2026-09-SPECIAL, Practical Test Banks Updates, p. 2]
Practice looking things up. Open the AC, find the chapter, find the paragraph, and write down the reference like you would in a logbook. A record entry must describe the work, or point to data acceptable to the Administrator. [14 CFR Part 43, § 43.9(a)(1)]
Next steps
- Read the full guide to getting your A&P.
- Take the free General diagnostic. It includes questions on regulations and records.
- Download AC 43.13-1B from the FAA. The link is on our sources page.
Questions people ask
- Is AC 43.13-1B approved data?
- Not by itself. It is acceptable data. It can be used as approved data for a major repair only when it fits the product, applies directly to the repair, and doesn't go against the manufacturer's data.
- Do I need AC 43.13-1B for the A&P tests?
- You need to know what it is and when to use it. The ACS lists the difference between approved and acceptable data as a General knowledge item. The practical test now leans on manuals and advisory circulars too.
- What is the difference between AC 43.13-1B and AC 43.13-2B?
- 1B covers inspection and repair. 2B covers alterations. Both are acceptable methods, techniques and practices published by the FAA.
Sources
Every fact above comes from one of these FAA or eCFR documents. Page numbers are the PDF page unless marked. The full list of what we use is on the sources page.
- AC 43.13-1B: Acceptable Methods, Techniques, and Practices: Aircraft Inspection and Repair (1B with Change 1)
- Paragraph 1, Purpose; Paragraph 3, Reference, p. 1
- Table of contents, chapter list, p. 2 to 16
- Purpose, p. 1
- 14 CFR Part 43: 14 CFR Part 43: Maintenance, Preventive Maintenance, Rebuilding, and Alteration (eCFR current as of 2026-10-28)
- § 43.13 Performance rules (general), p. 43.13
- § 43.9 Maintenance records, p. 43.9
- Appendix A, Major Alterations, Major Repairs, and Preventive Maintenance, p. Appendix A
- § 1.1 Definitions: major alteration, major repair, minor repair, p. 1.1
- FAA-S-ACS-1: Aviation Mechanic General, Airframe, and Powerplant Airman Certification Standards (November 2021 (effective September 21, 2022))
- AM.I.I.K15 and AM.I.I.K16, p. 19
- ATCA-2026-09-SPECIAL: Airman Testing Community Advisory, September 2026 Special Edition (September 2026 Special Edition)
- Practical Test Banks Updates, p. 2