Aircraft Structural Components Questions and Answers

Answer: C

No one method dominates, which is why a modern airframe uses all four in different places. The choice at each location follows from whether stiffness, strength, inspectability or cost is the governing consideration there.

Answer: D

Airframe layout is the discipline of load paths: wherever a concentrated load enters a thin shell, a fitting or a heavy frame appears to spread it, and wherever a path is interrupted, weight follows. Everything else, material choice included, is subordinate to getting those paths right.

Answer: A

Removing skin interrupts both the hoop and the shear paths, so the load must divert round the opening and concentrates sharply at its corners. Heavy edge members, doublers and generously radiused corners are the standard treatment, and square corners have caused fatal accidents.

Answer: B

A sharp corner produces a severe local stress peak in a pressurised shell, and the early Comet failures made the consequence unmistakable. Rounding the corner spreads the flow of stress and raises the fatigue life by orders of magnitude.

Answer: C

The doubler restores the section that the opening removed, in the region where the load must flow round it. Sizing it is a balance: too little and the corner stress stays high, too much and the stiffness discontinuity simply moves the problem to the doubler's own edge.

Answer: D

The flow acts over the length of the opening, so \( 90 \times 1.0 = 90 \) kN must find another path. Spreading that load into the surrounding structure without a large local stress peak is what the edge members and doublers are sized to do.

Answer: A

Both are true and the second is the reason for the first. The lesson was learned at considerable cost with the early Comet, whose near-square cut-out corners initiated fatigue cracks that led to the loss of the aircraft. Corner radii are now a fundamental design rule.

Answer: B

The first two are correct. The third ignores the catch: an over-thick doubler creates a sharp stiffness discontinuity at its own edge, and the fatigue problem simply relocates there. Doubler sizing is a balance rather than a maximisation.

Answer: C

Correct answer: The cabin pressure is locally higher at an opening

Pressure is uniform throughout the cabin; an opening does not raise it locally. The real difficulties are all structural: the load carried by the removed material must divert around the opening, that diversion concentrates stress at the corners, and the surrounding structure needs local reinforcement to carry it - which is why doors and windows have rounded corners and heavy surrounding frames.

Answer: D

The four measures work together rather than separately: the radius lowers the peak, the doubler and edge member carry the diverted load, and the tear strap accepts that a crack may still start and confines it when it does.