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Reuse of an elastic stop nut

Aviation Mechanic General (AMG) practice question 10 of 33 on Aircraft Materials, Hardware, and Processes. ACS element AM.I.E.R3 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONDuring reassembly, a mechanic finds that a previously used elastic stop nut can be run onto the bolt with the fingers. What action is required?

  1. AReplace the nut
  2. BInstall it and safety wire it as a backup
  3. CInstall it after tapping the fiber insert
Show the answer and explanation

Correct answer: A. Replace the nut

  • A — correct When reusing elastic stop nuts, the fiber must not have lost its locking friction; the handbook states that if a nut can be turned with the fingers, it must be replaced.
  • B — incorrect A nut that turns by hand has lost its locking friction and must be replaced, not supplemented with safety wire.
  • C — incorrect The handbook specifically says not to tap the fiber locking insert; its self-locking action depends on the bolt threads impressing themselves into untapped fiber.

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's thread diameter, so the bolt threads impress themselves into the fiber and create pressure that holds the nut even under severe vibration. Normally, elastic stop nuts can be used many times with complete safety and without detriment to their locking efficiency. When reusing them, the mechanic must be sure the fiber has not lost its locking friction or become brittle. If a nut can be turned with the fingers, it must be replaced. The fiber insert must never be tapped.

STUDY TIP

Reuse of self-locking nuts is allowed, but the finger-turn check is the pass/fail test.

KEY POINTS

  • Elastic stop nuts may be reused many times if the fiber still locks.
  • A nut that turns with the fingers must be replaced.
  • Never tap the fiber locking insert.

SOURCES

  • FAA-H-8083-30B ch07 "Elastic Stop Nut"
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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.