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Instrument used to check heat-exposed aluminum structure

Aviation Mechanic General (AMG) practice question 22 of 23 on Inspection Concepts and Techniques. ACS element AM.I.K.K5 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONAn aluminum aircraft structure that was exposed to intense heat shows no visible damage and passes a visual inspection, but its strength is still suspect. Which instrument is used to further determine its strength and airworthiness?

  1. AA conductivity tester
  2. BA Rockwell C hardness tester
  3. CAn ultrasonic thickness gauge
Show the answer and explanation

Correct answer: A. A conductivity tester

  • A — correct For an aluminum structure that passes visual inspection but is still suspect after heat exposure, strength and airworthiness can be further determined with a conductivity tester, a device that uses eddy current.
  • B — incorrect A hardness tester such as the Rockwell C is the instrument named for possible heat damage to steel structures, because strength of metals is related to hardness, not for suspect aluminum.
  • C — incorrect Direct reading ultrasonic units measure material thickness, and heat exposure that degrades design strength does not change the thickness of the part.

BACKGROUND

Most structural metallic components of an aircraft have undergone some sort of heat-treatment process during manufacture, so an exposure to high heat not encountered during normal operations could severely degrade the design strength of the structure even when nothing looks burned or distorted. Inspection after fire or intense heat can be relatively simple when visible damage is present, because visible damage requires repair or replacement. The difficulty is the structure with no visible damage, whose structural integrity may still have been compromised, so the mechanic must reach for an instrument rather than the eye. For a suspect aluminum structure, the handbook names a conductivity tester, a device that uses eddy current. Since strength of metals is related to hardness, possible damage to steel structures might instead be determined with a hardness tester, such as a Rockwell C hardness tester.

STUDY TIP

Learn the fire damage passage as a pair: conductivity tester for aluminum, hardness tester for steel. Remembering why each works, electrical conductivity for aluminum and hardness for metal strength, keeps the two from being swapped on the test.

KEY POINTS

  • Heat exposure can degrade the design strength of metal structure with no visible damage.
  • Suspect aluminum that passes visual inspection is checked with a conductivity tester, an eddy current device.
  • Suspect steel is checked with a hardness tester such as a Rockwell C, since strength of metals relates to hardness.

SOURCES

  • FAA-H-8083-30B ch10 "Fire Damage"
Practice the Aviation Mechanic General (AMG) test →Timed 60-question exam, by ACS area, or review your misses. Free.
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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.