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Elastic stop nut temperature limit

Aviation Mechanic General (AMG) practice question 30 of 33 on Aircraft Materials, Hardware, and Processes. ACS element AM.I.E.K4 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONElastic stop nuts should not be installed in places where the temperature is higher than

  1. A450 °F.
  2. B212 °F, the boiling point of water.
  3. C250 °F.
Show the answer and explanation

Correct answer: C. 250 °F.

  • A — incorrect The limit is 250 °F, not 450 °F. The fiber locking collar loses effectiveness well before 450 °F.
  • B — incorrect The stated limit is 250 °F. The fiber collar is unaffected by immersion in hot or cold water, so the boiling point of water is not the limiting factor.
  • C — correct Above 250 °F the effectiveness of the fiber collar's self-locking action is reduced, so elastic stop nuts are not installed there.

BACKGROUND

The elastic stop nut is a standard nut with its height increased to accommodate a fiber locking collar. The collar is not threaded and its inside diameter is smaller than the bolt thread, so the bolt threads impress themselves into the untapped fiber, creating friction that locks the nut even under severe vibration. The fiber collar is unaffected by immersion in hot or cold water or ordinary solvents such as ether, carbon tetrachloride, oils, and gasoline. However, elastic stop nuts are not installed where the temperature is higher than 250 °F, because the self-locking effectiveness is reduced beyond that point. They may be used on engines and accessories when the engine manufacturer specifies their use.

STUDY TIP

Memorize 250 °F as the upper temperature limit for fiber-collar elastic stop nuts.

KEY POINTS

  • Elastic stop nuts lock by the bolt threads impressing into an untapped fiber collar.
  • Do not install them where temperatures exceed 250 °F.
  • Use on engines and accessories only when the engine manufacturer specifies it.

SOURCES

  • FAA-H-8083-30B ch07 "Elastic Stop Nut"
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MORE ON AIRCRAFT MATERIALS, HARDWARE, AND PROCESSES

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.