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Weighing with partially full fuel tanks

Aviation Mechanic General (AMG) practice question 18 of 25 on Weight and Balance. ACS element AM.I.C.K7 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA technician proposes to weigh an airplane with its fuel tanks about half full and then subtract the fuel weight. Why is this not acceptable?

  1. APartial fuel shifts the CG outside the empty weight CG range
  2. BThe hydrometer cannot read fuel density unless the tanks are completely full
  3. CIt is impossible to determine exactly how much fuel to account for
Show the answer and explanation

Correct answer: C. It is impossible to determine exactly how much fuel to account for

  • A — incorrect The objection is not about the CG range; it is that the exact fuel quantity, and therefore its weight and moment, cannot be established.
  • B — incorrect A hydrometer measures the density of a fuel sample in a flask; tank level does not affect it. The problem is the unknown quantity of fuel.
  • C — correct The handbook says never to weigh an aircraft with fuel tanks partially full because it will be impossible to determine exactly how much fuel to account for.

BACKGROUND

Empty weight includes only residual (unusable) fuel. To ensure that only residual fuel is accounted for, an aircraft is weighed in one of three conditions: with absolutely no fuel in the tanks or lines, after draining the tanks as the manufacturer specifies until the gauges read empty and fuel stops draining, or with the tanks completely full so that the usable fuel can be mathematically subtracted. In each case the weight and arm of the residual fuel come from the TCDS. An aircraft is never weighed with partially full tanks because the exact amount of fuel to account for cannot be determined.

STUDY TIP

Empty, drained, or completely full are the only acceptable fuel states for weighing.

KEY POINTS

  • Empty weight includes only unusable fuel.
  • Weigh with tanks empty, drained, or completely full.
  • Never weigh with partially full tanks.

SOURCES

  • FAA-H-8083-30B ch06 "Fuel System"
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MORE ON WEIGHT AND BALANCE

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.