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Castellated nut cotter pin hole alignment

Aviation Mechanic General (AMG) practice question 20 of 33 on Aircraft Materials, Hardware, and Processes. ACS element AM.I.E.R4 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA mechanic is tightening a castellated nut on a wing attach fitting bolt. Within the recommended torque range, the cotter pin hole does not line up with any slot in the nut. What should the mechanic do?

  1. ATighten past the maximum torque until the next slot lines up
  2. BRemove the hardware and realign the holes
  3. CBack the nut off to the nearest slot below the minimum torque
Show the answer and explanation

Correct answer: B. Remove the hardware and realign the holes

  • A — incorrect Over torquing to align cotter pin holes is allowed only in cases of highly stressed engine parts, not on an airframe fitting.
  • B — correct Except for highly stressed engine parts, the nut may not be over torqued to align the cotter pin hole. The hardware is removed and the holes are realigned, for example by changing washers.
  • C — incorrect Leaving the nut below the recommended torque range means the joint does not carry its designed load. The correct action is to realign the holes with the hardware.

BACKGROUND

When tightening castellated nuts on bolts, the cotter pin holes may not line up with the slots in the nut within the range of recommended torque values. Except in cases of highly stressed engine parts, the nut may not be over torqued; the hardware is removed and the holes realigned. Plain washers act as shims in obtaining correct grip length and are used to adjust the position of castellated nuts in respect to drilled cotter pin holes in bolts. The standard torque loads apply to unlubricated cadmium-plated steel nuts, and maximum torque ranges are used only when the materials and surfaces being joined can resist breaking, warping, or other damage.

STUDY TIP

For critical, highly stressed structural fasteners, keep the torque within its range and fix alignment problems with hardware, not with extra torque.

KEY POINTS

  • Cotter pin holes may not align within the recommended torque range.
  • Except for highly stressed engine parts, do not over torque; remove hardware and realign.
  • Plain washers are used to adjust castellated nut position relative to cotter pin holes.

SOURCES

  • FAA-H-8083-30B ch07 "Cotter Pin Hole Line Up"
  • FAA-H-8083-30B ch07 "Plain Washers"
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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.