SkyDrill

Replacement of an internal wrenching bolt

Aviation Mechanic General (AMG) practice question 14 of 33 on Aircraft Materials, Hardware, and Processes. ACS element AM.I.E.K9 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONAn internal wrenching bolt in a high-strength fitting must be replaced. What may be used in its place?

  1. AA standard AN hex head bolt of the same diameter and grip
  2. BA close tolerance NAS bolt with a heat-treated washer
  3. COnly another internal wrenching bolt
Show the answer and explanation

Correct answer: C. Only another internal wrenching bolt

  • A — incorrect Standard AN hex head bolts and washers cannot be substituted because they do not have the required strength.
  • B — incorrect Close tolerance bolts are used where a tight drive fit is required; they are not named as a substitute for an internal wrenching bolt, and only another internal wrenching bolt is acceptable.
  • C — correct The handbook directs that an internal wrenching bolt be replaced with another internal wrenching bolt.

BACKGROUND

Internal wrenching bolts (MS-20004 through MS-20024 or NAS-495) are fabricated from high-strength steel and are suitable for both tension and shear applications. When used in steel parts, the bolt hole must be slightly countersunk to seat the large corner radius of the shank at the head, and in Dural material a special heat-treated washer provides an adequate bearing surface. The head is recessed for an internal wrench, and special high-strength nuts are used. An internal wrenching bolt must be replaced with another internal wrenching bolt; standard AN hex head bolts and washers cannot be substituted because they lack the required strength.

STUDY TIP

When a fastener is chosen for strength, replace it like for like; the handbook's general rule is to use a duplicate of the original fastener whenever possible.

KEY POINTS

  • Internal wrenching bolts are high-strength steel bolts for tension and shear.
  • Replace them only with another internal wrenching bolt.
  • Standard AN hex head bolts lack the required strength.

SOURCES

  • FAA-H-8083-30B ch07 "Internal Wrenching Bolts"
Practice the Aviation Mechanic General (AMG) test →Timed 60-question exam, by ACS area, or review your misses. Free.
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.