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Checking a measured part against a plus-or-minus tolerance

Aviation Mechanic General (AMG) practice question 1 of 15 on Aircraft Drawings. ACS element AM.I.B.K3 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA dimension on a print is 0.225 plus or minus 0.0025. A finished part measures 0.2280 at that dimension. Is the part acceptable?

  1. ANo; it exceeds the maximum of 0.2275
  2. BYes; it lies within the 0.0050 total tolerance
  3. CNo; it is below the minimum of 0.2225
Show the answer and explanation

Correct answer: A. No; it exceeds the maximum of 0.2275

  • A — correct The plus allowance of 0.0025 makes the maximum 0.225 plus 0.0025, or 0.2275; a part measuring 0.2280 is 0.0030 over the given dimension and outside the allowed variation.
  • B — incorrect The 0.0050 tolerance is the sum of the plus and minus allowances; the part may not exceed the given dimension by more than the plus figure of 0.0025.
  • C — incorrect The minimum is 0.2225, but the part measures more than the given dimension, so the problem is the upper limit, not the lower one.

BACKGROUND

When the plus and minus allowances are equal, the drawing shows them as a single plus-or-minus figure, such as 0.225 plus or minus 0.0025, and the tolerance is 0.0050. The plus figure is the maximum allowable variation above the dimension and the minus figure the minimum allowable variation below it. The part is acceptable only if it is not more than 0.0025 larger or 0.0025 smaller than 0.225. A measurement of 0.2280 is 0.0030 over the stated dimension, which is more than the 0.0025 allowed, so the part does not conform.

STUDY TIP

Compare the measurement with each limit separately; the total tolerance band is not the amount a single measurement may deviate.

KEY POINTS

  • 0.225 plus or minus 0.0025 gives limits of 0.2275 and 0.2225.
  • A part measuring 0.2280 exceeds the upper limit by 0.0005.
  • The total tolerance of 0.0050 is the width of the band, not the allowed deviation in one direction.

SOURCES

  • FAA-H-8083-30B ch04 "Allowances & Tolerances"
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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.