Aircraft Structural Components Questions and Answers

Answer: C

Removing the stringers lengthens every skin panel enormously, and buckling rather than material strength then sets the thickness. The skin needed would weigh far more than the stringers saved, which is precisely why semi-monocoque construction is universal at this size.

Answer: D

Wagner's diagonal tension theory shows a buckled web carries far more than its buckling load as inclined tension bands, and designing for that state deliberately saves weight. The flanges and uprights must be sized for the inward pull it produces.

Answer: A

Correct answer: Formers are heavier than frames and carry concentrated loads

That reverses the two. Frames are the heavier, stronger members that maintain the section and take concentrated loads from the wing, undercarriage and tail attachments; formers are lighter and sit between them simply to hold the skin to shape. The other three statements are all correct.

Answer: B

The fairing carries no flight, ground or pressure load whose loss would hazard the aircraft, so it is secondary structure. The other three carry loads whose failure would be critical and attract the full weight of certification and inspection control.

Answer: C

A margin of safety is the allowable over the applied, less one, so a negative value means the applied load exceeds the allowable and the member is inadequate. Zero means exactly at the allowable, and positive values indicate reserve.

Answer: D

Correct answer: A dome is easier to manufacture than a flat plate

A dome is decidedly harder to make than a flat plate - it must be formed or built from segments, and it is the manufacturing cost that is accepted rather than a saving. What is gained is structural: the dome carries the pressure largely in membrane tension, which stresses the material uniformly through the thickness, while a flat plate would carry it in bending and be far heavier for the same strength.

Answer: A

The two are distinct. Placing area ahead of the hinge reduces the effort the pilot or actuator must supply, while placing mass ahead of it moves the centre of gravity forward and decouples rotation from bending. Only the second bears on flutter.

Answer: B

Correct answer: Rivet holes introduce no stress concentration

A rivet hole is a stress concentration - a factor of about three for a circular hole in a wide plate - and rivet holes are among the commonest fatigue origins in an airframe. Riveting persists in spite of that, for the three genuine reasons given: field repairability, individual inspection and replacement, and decades of fatigue data behind the design allowables.

Answer: C

Cutting the stiffeners from solid removes every fastener hole and the fatigue origins that go with them, and gives a clean aerodynamic surface. The penalties are the material machined away and the difficulty of repair, since a damaged stringer cannot simply be unbolted.

Answer: D

The facesheets act as the flanges of a beam and the core simply holds them apart while carrying the shear between them. Since stiffness grows with the square of the separation, a very light core buys a great deal, which is why sandwich is used for floors and control surfaces.