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Weight balance practice questions

24 questions from the aviation mechanic general practice test.

Weight balance practice test

10 questions, graded as you go, with the reason for every answer. No sign-up.

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Sample questions

An engine's oil system holds 8 qt. Using the standard weight for lubricating oil, how much does the oil weigh?

Answer in lb.

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15 lb

8 qt ÷ 4 = 2 gal. Oil is taken as 7.5 lb per gallon: 2 × 7.5 = 15 lb.

Reference: FAA-H-8083-30, Weight and Balance (standard weights)

An airplane has a maximum gross weight of 2,550 lb and an empty weight of 1,640 lb. What is its useful load?

Answer in lb.

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910 lb

Useful load = maximum weight − empty weight = 2,550 − 1,640 = 910 lb.

Reference: FAA-H-8083-30, Weight and Balance (terminology)

The datum is at the firewall. A 30 lb item is mounted 10 in forward of the datum. What is its moment?

  1. Plus 300 lb-in
  2. Minus 3 lb-in
  3. Minus 300 lb-in
  4. Plus 40 lb-in
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C. Minus 300 lb-in

Arms ahead of the datum are negative, so the moment is 30 × (−10) = −300 lb-in. Entering it as positive would shift the computed center of gravity aft of where it really is.

Reference: FAA-H-8083-30, Weight and Balance (weight, arm and moment)

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