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Confirming an integral tank is safe to enter

Aviation Mechanic Airframe (AMA) practice question 1 of 12 on Aircraft Fuel Systems. ACS element AM.II.J.R3 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA large integral fuel tank has been defueled, dried, and vented of vapors. What confirms that it can be entered safely?

  1. AA pressure check of the tank structure
  2. BA test with a combustible-gas indicator
  3. CA visual check for pooled fuel and sludge
Show the answer and explanation

Correct answer: B. A test with a combustible-gas indicator

  • A — incorrect Pressure checks verify the soundness of a repair or the absence of leaks; they say nothing about the vapor level inside.
  • B — correct After drying and venting, the tank is tested with a combustible-gas indicator to be certain it can be entered safely.
  • C — incorrect A visual check cannot establish that ignitable vapor has been removed, which is the hazard that governs entry.

BACKGROUND

Integral tank leaks occur when the sealant on tank seams loses its integrity, and repairing them on a transport category aircraft means entering the tank. Preparing the tank for safe entry follows a series of manufacturer steps that include transferring or defueling the fuel, drying the tank, and venting it of dangerous vapors. The tank is then tested with a combustible-gas indicator before anyone goes in. The technician wears clothing that does not cause static electricity along with a respirator, an observer is stationed outside to assist, and a continuous flow of ventilating air is maintained through the tank. Empty fuel tanks retain ignitable vapor for a long time, so purging is an absolute necessity before any repair is started.

STUDY TIP

For any tank entry question, look for the combination of purge, gas test, respirator, outside observer, and continuous ventilation.

KEY POINTS

  • Dry and vent the tank, then verify with a combustible-gas indicator.
  • An outside observer and continuous ventilating airflow are required.
  • Empty tanks hold ignitable vapor long after the liquid fuel is gone.

SOURCES

  • sources/ama-airframe/ch14.txt, "Integral Tanks" (Fuel Tank Repair)
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MORE ON AIRCRAFT FUEL SYSTEMS

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.