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First requirement when substituting aircraft metals

Aviation Mechanic General (AMG) practice question 15 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

QUESTIONWhen selecting a substitute metal for the repair of an aircraft structure, what is the first and most important requirement?

  1. AMaintaining the original weight of the structure, if possible
  2. BMaintaining contour and aerodynamic smoothness
  3. CMaintaining the original strength of the structure
Show the answer and explanation

Correct answer: C. Maintaining the original strength of the structure

  • A — incorrect Keeping the original weight, or holding added weight to a minimum, is one of the other three requirements, not the most important one.
  • B — incorrect Maintaining contour or aerodynamic smoothness is one of the remaining three requirements, ranked after strength.
  • C — correct The handbook lists four requirements for substitute metals and names maintaining the original strength of the structure as the first and most important.

BACKGROUND

In selecting substitute metals for repair and maintenance, it is very important to check the appropriate structural repair manual, because manufacturers design structural members to meet a specific load requirement and repair methods vary between aircraft. Four requirements must be kept in mind. The first and most important is maintaining the original strength of the structure. The other three are maintaining contour or aerodynamic smoothness; maintaining original weight, if possible, or keeping added weight to a minimum; and maintaining the original corrosion-resistant properties of the metal.

STUDY TIP

Learn all four substitution requirements, but remember that strength comes first.

KEY POINTS

  • Check the structural repair manual before substituting metals.
  • The first and most important requirement is maintaining original strength.
  • The others are contour, weight, and corrosion resistance.

SOURCES

  • FAA-H-8083-30B ch07 "Substitution of Aircraft Metals"
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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.