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Definition of tolerance

Aviation Mechanic General (AMG) practice question 9 of 15 on Aircraft Drawings. ACS element AM.I.B.K3 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONOn an aircraft drawing, the tolerance of a dimension is defined as

  1. Athe plus figure alone, which sets the maximum size.
  2. Bthe sum of the plus and minus allowance figures.
  3. Cthe difference between the plus and minus figures.
Show the answer and explanation

Correct answer: B. the sum of the plus and minus allowance figures.

  • A — incorrect The plus figure is only the maximum allowable variation; tolerance combines it with the minus figure.
  • B — correct The handbook defines tolerance as the sum of the plus and minus allowance figures; the plus figure is the maximum and the minus figure the minimum allowable variation.
  • C — incorrect Tolerance is the sum of the two allowance figures, not their difference.

BACKGROUND

When a dimension on a print shows an allowable variation, the plus figure indicates the maximum and the minus figure the minimum allowable variation from the given dimension. The sum of the plus and minus allowance figures is called the tolerance. For example, a dimension of 0.225 with +0.0025 and -0.0005 has a tolerance of 0.0030. When the plus and minus allowances are equal, they are written with a plus-or-minus sign, such as 0.225 plus or minus 0.0025, which gives a tolerance of 0.0050.

STUDY TIP

Remember that tolerance is a total band: add the plus allowance and the minus allowance together.

KEY POINTS

  • The plus figure is the maximum allowable variation; the minus figure is the minimum.
  • Tolerance equals the sum of the plus and minus allowances.
  • Equal allowances are written with a plus-or-minus sign.

SOURCES

  • FAA-H-8083-30B ch04 "Allowances & Tolerances"
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MORE ON AIRCRAFT DRAWINGS

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.