Weight Estimation Methods Questions and Answers

Answer: C

Correct answer: Invalid; the definitions differ

Manufacturer’s empty weight is the aircraft as built; operating empty weight adds crew, oil, catering and emergency equipment, and can be several tonnes higher on a transport. Comparing one against the other flatters whichever aircraft is quoted on the lower definition. Weight comparisons are only meaningful when both figures are on the same definition, which is why weight statements name it explicitly.

Answer: D

Correct answer: Elevator power to rotate and flare

With the centre of gravity forward the aircraft is more stable, not less, so stability is not what runs out. What runs out is control: the elevator must produce a nose-up moment large enough to rotate at take-off speed and to flare for touchdown, and beyond a certain forward position the deflection required exceeds what is available. Wing bending and tank position set other limits, not this one.

Answer: A

Correct answer: Growth is best judged at the end

This is false, and it is the belief that weight control exists to prevent. By the end of a programme the design is frozen and the weight is whatever it is; the moment to detect growth is while the increments are still small and the design still open. The other three statements are correct, and together they describe how that early detection is achieved.

Answer: B

Correct answer: Increasing the design load factor

A higher design load factor makes the structure carry more, so the wing and fuselage get heavier - it increases operating empty weight rather than reducing it. The other three all remove weight: fewer galleys, lighter seats, and composite skins that give the same strength for less mass.

Answer: C

Twice the typical fraction suggests a mistake in the calculation or in the units rather than a genuine design outcome. Comparing group fractions against expected ranges is one of the quickest checks available on a weight estimate.

Answer: D

Correct answer: Determining maximum take-off weight

Moments of inertia describe how mass is distributed about the axes, and so govern how quickly the aircraft responds in roll and pitch, how it behaves in a handling qualities assessment, and where its structural modes lie for flutter analysis. Maximum take-off weight is a matter of structural strength and performance, and follows from mass alone, not from its distribution.

Answer: A

Correct answer: Segment ratios are multiplied, not added

Each fraction is the ratio of weight at the end of a segment to weight at the start, so the overall ratio is their product - the output of one segment is the input to the next. Adding them would give a number greater than one, which is meaningless. The cruise segment usually dominates the product, but every segment contributes, and reserves are added afterwards.

Answer: B

Correct answer: To move the centre of gravity aft

Trimming the centre of gravity aft in cruise reduces the download the tailplane must carry, and that download is a real drag penalty because the wing has to lift it as well as the aircraft. Pumping fuel to a tail tank buys that saving over the long cruise where it matters most, and the fuel is pumped forward again before descent to keep the landing case within limits.

Answer: C

With the centre of gravity at the neutral point the pitching moment does not vary with angle of attack, so the aircraft is neither stable nor unstable. The distance between the two, expressed in mean aerodynamic chord, is the static margin.

Answer: D

A positive static margin means the centre of gravity lies ahead of the neutral point and the aircraft is statically stable. Transports typically carry five to fifteen per cent, while relaxed stability fighters run at or beyond zero.