The center of gravity (CG) of an aircraft is best described as the point where the aircraft would
ACS code: AM.I.C
Correct answer: balance if it were suspended
Rationale: The center of gravity is the point about which the nose-heavy and tail-heavy moments are exactly equal; it is the point at which the aircraft would balance if suspended. It is found by dividing total moment by total weight. The other options describe stall behavior and ground contact, which are unrelated to the definition of CG.
The moment of an item in a weight and balance computation is found by
ACS code: AM.I.C
Correct answer: multiplying the weight by its arm
Rationale: Moment equals weight multiplied by arm, expressed in inch-pounds. This is the basic relationship used to build a weight and balance computation, where the total moment is divided by total weight to find the CG. Dividing or subtracting the values does not yield a valid moment and would produce incorrect balance results.
An aircraft has a total weight of 4,000 pounds and a total moment of 600,000 inch-pounds. The center of gravity is located at
ACS code: AM.I.C
Correct answer: 150 inches from the datum
Rationale: The CG is found by dividing total moment by total weight: 600,000 ÷ 4,000 = 150 inches from the datum. The other answers result from incorrect arithmetic, such as using the wrong divisor, and do not satisfy the moment-divided-by-weight relationship.
Useful load is determined by
ACS code: AM.I.C
Correct answer: subtracting the empty weight from the maximum allowable weight
Rationale: Useful load is the difference between maximum allowable (gross) weight and empty weight; it represents the crew, payload, and usable fuel the aircraft can carry. Reversing the subtraction yields a negative value and adding the two weights together produces a meaningless total, so those distractors are incorrect.
An arm measured forward of the datum is given which sign in weight and balance computations?
ACS code: AM.I.C
Correct answer: Negative
Rationale: By convention, arms measured aft of the datum are positive and arms measured forward of the datum are negative. Correctly applying these signs is essential so the resulting moments add and subtract properly. Assigning a positive or zero value to a forward arm would corrupt the moment calculation.
Ballast is added to an aircraft primarily to
ACS code: AM.I.C
Correct answer: bring the center of gravity within allowable limits
Rationale: Ballast is weight added to move the CG into the allowable range, most often when the CG falls outside limits after loading or a modification. It does not raise the certificated maximum gross weight and, since it adds weight, it cannot reduce empty weight, making those distractors incorrect.
When weighing an aircraft, the weight registered on the scales minus the weight of chocks, blocks, and other items used to level the aircraft is called the
ACS code: AM.I.C
Correct answer: net weight at each weighing point
Rationale: The net weight at each weighing point is the scale reading minus the tare, where tare is the weight of chocks, blocks, and similar items on the scale. Tare itself is what is subtracted, not the resulting value, and useful load is an entirely different quantity unrelated to scale tare.