Loads on Aircraft Structures Questions and Answers

Answer: A

A real gust builds up over a distance rather than striking instantaneously, and the aircraft starts to accelerate upward during that build-up, which reduces the angle-of-attack change it actually experiences. The factor, always less than one, corrects the idealised sharp-edged gust result.

Answer: B

The gust produces a lift increment that is divided by the weight to give the load factor, so a higher wing loading dilutes it. This is why a transport is most vulnerable to gust loads when it is light, and why the gust envelope must be checked at several weights.

Answer: C

VD is the design dive speed, reached in an upset or an emergency descent, and it sets the right-hand boundary of the envelope. VC, the design cruising speed, sits below it with a margin chosen so that an inadvertent overspeed does not immediately exceed the design condition.

Answer: D

The ground load cases are frequently critical for the undercarriage and its attachment structure, and a heavy landing or a braked roll over rough ground can exceed anything the airframe meets in flight. They are analysed as a separate family from the flight loads.

Answer: A

The gear must absorb the vertical kinetic energy of the descent, so the design sink rate, typically around three metres per second for a transport, together with the stroke and characteristics of the shock absorber, fixes the load. Doubling the sink rate quadruples the energy to be absorbed.

Answer: B

The wing's own weight and that of the fuel and engines it carries act opposite to the lift, so the net bending moment at the root is less than the lift alone would give. Distributing mass outboard is therefore structurally beneficial, which is one reason wing-mounted engines and wing tanks are used.

Answer: C

Correct answer: Outboard fuel preserves inertia relief

Fuel held in the outboard tanks sits beyond most of the wing structure, and its weight acts downwards against the lift acting upwards, so it relieves the bending moment at the root rather than adding to it. Burning the inboard fuel first therefore keeps that relief in place for as long as possible, which is why the outboard tanks are emptied last.

Answer: D

The wing is sized by the largest bending moment it must carry, which comes from the positive manoeuvre limit or from a severe gust at high weight, whichever proves greater. Pressurisation governs the fuselage instead, and ground loads govern the gear and its attachments.

Answer: A

Static strength asks whether one extreme load can be carried; fatigue asks whether millions of smaller cycles will grow a crack. The pressurisation cycle, the gust spectrum and the ground-air-ground cycle together make up the load spectrum a transport is assessed against.

Answer: B

On the ground the wing hangs down under its own weight and the gear reaction; in flight it bends upward under lift. That full reversal happens once per flight and is one of the largest single contributors to the fatigue damage a wing accumulates.