SkyDrill

Ideal moisture content for wood structure inspection

Aviation Mechanic Airframe (AMA) practice question 11 of 30 on Non-Metallic Structures. ACS element AM.II.B.K1 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONWhen a moisture meter is used to verify the condition of a wood aircraft structure, what is the ideal percentage of moisture in the wood?

  1. A8 to 12 percent
  2. B20 to 25 percent, taken at the spar
  3. C2 to 5 percent, taken at the glue line
Show the answer and explanation

Correct answer: A. 8 to 12 percent

  • A — correct The handbook states that the ideal moisture range for a wood aircraft structure is 8 to 12 percent.
  • B — incorrect Any reading over 20 percent provides an environment for the growth of fungus in the wood, so this range is far above the ideal.
  • C — incorrect No such range is given; the stated ideal begins at 8 percent, and readings are taken of the structure rather than only at a glue line.

BACKGROUND

A wood aircraft must be dry before it can be properly inspected. It should be placed in a dry, well-ventilated hangar with inspection covers, access panels, and removable fairings opened or removed so interior sections can dry thoroughly. Wet or even damp wood swells, which makes it difficult to judge the condition of the glue joints. When there is any doubt that the wood is dry, a moisture meter is used, and nondestructive meters are available that check moisture without making holes in the surface. The ideal range is 8 to 12 percent, and any reading over 20 percent provides an environment for fungal growth.

STUDY TIP

Memorize the two numbers that bracket this topic: 8 to 12 percent is ideal, and over 20 percent invites fungus. Also remember that drying the aircraft comes before any judgment about glue joints.

KEY POINTS

  • The ideal moisture content of aircraft wood is 8 to 12 percent.
  • A reading over 20 percent creates conditions for fungal growth.
  • The aircraft must be dry before glue joints can be properly judged.

SOURCES

  • ama-airframe/ch06.txt "Inspection of Wood Structures"
Practice the Aviation Mechanic Airframe (AMA) test →Timed 100-question exam, by ACS area, or review your misses. Free.
MORE ON NON-METALLIC STRUCTURES

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.