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AC revision letter meaning

Aviation Mechanic General (AMG) practice question 18 of 37 on Regulations, Maintenance Forms, Records, and Publications. ACS element AM.I.I.K10 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONAn advisory circular is numbered AC 43.13-2B. Under the advisory circular numbering system described in the handbook, what does the letter B indicate?

  1. AThe AC is in its second revision
  2. BThe AC applies to part 43, subpart B
  3. CThe AC is the second circular issued on the subject
Show the answer and explanation

Correct answer: A. The AC is in its second revision

  • A — correct The third part of an AC number is a letter showing the revision sequence; the first version has no letter, so A is the first revision and B the second.
  • B — incorrect The subject-matter part is identified by the first part of the number (43), and the letter has nothing to do with subparts.
  • C — incorrect The sequential position within a subject area is shown by the number after the dash (here 2), not by the letter.

BACKGROUND

The Federal Aviation Administration (FAA) issues advisory circulars (ACs) to provide non-regulatory guidance, and the Aviation Maintenance Technician Handbook–General explains their three-part numbering system using the example 25-42-C. The first part identifies the subject matter area and corresponds to the part of the regulations, such as part 25. The second part, beginning with the dash, is a sequential number within that subject area, so 42 means the 42nd AC relating to part 25. The third part is a letter assigned by the originating office showing the revision sequence; the first version of an AC has no revision letter, and in the example the C designates the third revision. Applying the same logic, a B designates the second revision. The handbook also reproduces the cover of AC 43.13-2B, which cancels AC 43.13-2A.

STUDY TIP

Decode AC numbers piece by piece: part number, then sequence within the part, then revision letter, remembering that the original issue carries no letter.

KEY POINTS

  • An AC number has three parts: subject area, sequential number, and revision letter.
  • The first version of an AC has no revision letter.
  • A means first revision, B means second revision, C means third revision.

SOURCES

  • FAA-H-8083-30B ch02 "The AC Numbering System"
  • FAA-H-8083-30B ch02 Figure 2-9, AC 43.13-2B excerpt
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.