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Reuse of a loose elastic stop nut

Aviation Mechanic General (AMG) practice question 21 of 33 on Aircraft Materials, Hardware, and Processes. ACS element AM.I.E.K4 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONWhile reinstalling a previously used elastic stop nut, a mechanic finds it can be turned onto the bolt with the fingers. What should the mechanic do?

  1. AReuse it if the fiber collar is not cracked
  2. BTap the fiber insert to restore its grip
  3. CReplace the nut
Show the answer and explanation

Correct answer: C. Replace the nut

  • A — incorrect A visually intact collar is not enough. The test is locking friction; a nut that turns with the fingers is replaced.
  • B — incorrect The fiber locking insert must not be tapped. Once the fiber has lost its friction, the nut is replaced rather than reworked.
  • C — correct If an elastic stop nut can be turned with the fingers, the fiber has lost its locking friction and the nut must be replaced.

BACKGROUND

Elastic stop nuts can normally 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 is replaced. The fiber locking insert is never tapped, and bolts with damaged threads or rough ends are not acceptable with these nuts. After tightening, the rounded or chamfered end of the bolt should extend at least the full round or chamfer through the nut; flat-end bolts should extend at least 1/32 inch through the nut.

STUDY TIP

Finger-tight on installation means the locking friction is gone; replace the nut rather than trying to salvage it.

KEY POINTS

  • Elastic stop nuts may be reused if the fiber still has locking friction and is not brittle.
  • A nut that can be turned with the fingers is 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.