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Tightening nuts on a replacement window panel

Aviation Mechanic Airframe (AMA) practice question 18 of 30 on Non-Metallic Structures. ACS element AM.II.B.K25 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA mechanic is bolting a replacement transparent plastic panel into its mounting. How should each nut be tightened?

  1. ATo a firm fit, then backed off one full turn
  2. BTo the torque value specified for metal panels
  3. CUntil the gasket is fully compressed
Show the answer and explanation

Correct answer: A. To a firm fit, then backed off one full turn

  • A — correct Each nut is tightened to a firm fit and then backed off one full turn so it is snug but can still be rotated with the fingers.
  • B — incorrect Overtorquing can easily develop more than 1,000 psi on the plastic, which is why a metal torque value is not applied here.
  • C — incorrect Gaskets are used to distribute stress and waterproof the installation, but the plastic must not be placed under excessive compressive stress.

BACKGROUND

A replacement panel is installed using the same mounting method the aircraft manufacturer used, and a panel is never forced out of shape to make it fit a frame. In clamping or bolting a plastic panel, the plastic must not be placed under excessive compressive stress, because more than 1,000 psi can easily be developed by overtorquing a nut and bolt. Each nut is tightened to a firm fit and then backed off one full turn. Spacers, collars, shoulders, or stop-nuts are used to prevent overtightening, and panels are mounted between rubber, cork, or other gasket material. Holes through the plastic are made oversize by 1/8 inch so the panel does not bind or crack at the hole edges.

STUDY TIP

Group the installation rules around one idea: plastic expands, contracts, and cracks, so every step exists to leave it free to move. The one full turn backoff, the oversize holes, and the spacers all serve that purpose.

KEY POINTS

  • Nuts are tightened to a firm fit and then backed off one full turn.
  • Overtorquing can put more than 1,000 psi on the plastic.
  • Holes through the panel are made 1/8 inch oversize.

SOURCES

  • ama-airframe/ch07.txt "Installation Procedures"
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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.