Weight Estimation Methods Questions and Answers

Answer: A

Manufacturer's empty weight covers the aircraft as built; operating empty weight adds the crew, unusable fuel, engine oil, catering equipment and everything else needed to put it into service. The distinction matters when comparing published figures.

Answer: B

It is the weight with everything aboard except usable fuel, and it is limited structurally because fuel in the wings provides bending relief. Exceeding it overloads the wing root even though the total weight may be within limits.

Answer: C

Payload sits in the fuselage and adds to the bending the wing root must carry, while wing fuel opposes it. An aircraft can therefore be within its take-off weight limit and still overload the wing if too much of that weight is payload.

Answer: D

The gear and backup structure are sized for a landing impact at a weight lower than the aircraft may take off at, since fuel is normally burned en route. A return shortly after departure may therefore require fuel jettison or an overweight landing inspection.

Answer: A

Correct answer: Statistical fractions applied at aircraft level

A Class I estimate is made at the very start of a design, when nothing is defined in detail. It takes the take-off weight and applies fractions drawn from a database of similar aircraft - an empty weight fraction, a fuel fraction - to get a first consistent set of weights. It is quick and it closes the sizing loop; what it cannot do is tell you which group is heavy, because it never looks below aircraft level.

Answer: B

Wing, fuselage, empennage, undercarriage, propulsion and systems are each estimated from relationships involving their own driving parameters. It is more work but far more informative, since it shows where the weight actually is.

Answer: C

Correct answer: Analysis of actual defined parts

Fidelity rises through the three classes. Class I uses aircraft-level fractions, Class II uses statistical formulae for each major group, and Class III weighs the design itself - part by part, from the actual geometry and material of what has been drawn. It is the most accurate and the most expensive, and it can only be done once there is a definition to analyse.

Answer: D

Each segment has a characteristic ratio of end weight to start weight, historical for short phases and computed by Breguet for cruise and loiter. Multiplying them through gives the overall ratio and hence the fuel required.

Answer: A

Regulatory reserves, a diversion allowance and fuel that cannot be pumped out all add to the mission figure. A factor of about six per cent is a common conceptual allowance, refined later against the actual reserve policy.

Answer: B

The wing must carry the bending moment produced by the aircraft's weight at its limit load factor, so span and loading dominate. High aspect ratio raises the weight for a given area, which is the structural half of the aspect ratio trade.