DGCA Technical General: Landing Gear, Wheels & Brakes Questions

Correct answer: C. Cantilever fork half fork dual wheel

The four undercarriage arrangements illustrated are, in order, cantilever, fork, half fork and dual wheel: a cantilever leg carries the wheel on a stub axle from a single rigid member, a fork straddles the wheel supporting the axle on both sides, a half fork supports the axle from one side only, and the dual-wheel unit mounts two wheels on a common axle.

Correct answer: C. Making tight turns when taxying

The torque links (scissor links) hold the two halves of the oleo strut in rotational alignment, so they are loaded most heavily when the wheel is being turned relative to the strut, as in tight turns while taxiing. That twisting is exactly what the links are designed to resist.

Correct answer: D. 1,5.

With no inner tube there is nothing to chafe or rotate inside the cover, and there is no separate tube valve that creep could shear off. However, the tyre itself can still creep on the rim, creep does not deflate a tubeless tyre, and they are not notably easier to fit.

Correct answer: D. Microswitches.

Microswitches operated by the compression of the landing gear legs, the weight-on-wheels or squat switches, signal that the aircraft is on the ground and prevent the retraction circuit from operating. A ground lock solenoid typically blocks the selector until the aircraft is airborne.

Correct answer: B. limit the speed of extension and compression of the strut

The oil in an oleo strut is forced through restrictor orifices, damping movement in both directions so that neither compression on touchdown nor extension (recoil) happens too quickly; it is the compressed gas charge, not the oil, that actually supports the aircraft's weight.

Correct answer: B. Release excessive tyre pressures to prevent wheel/tyre explosions.

Thermal plugs in the wheel rim melt at a set temperature when brake heat soaks into the wheel, releasing the tyre pressure in a controlled way. This prevents the overheated wheel and tyre assembly from exploding.

Correct answer: B. can be measured by painting marks on the tyre and wheel rim

Creep is the slow rotation of the tyre relative to its wheel rim; aligned paint marks applied across the tyre and rim make any relative movement immediately visible on inspection so excessive creep can be caught before it tears out the inflation valve.

Correct answer: B. High temperatures.

Fusible plugs have a core of low melting point alloy that melts when the wheel reaches a dangerously high temperature, deflating the tyre safely. They respond purely to temperature, not to pressure.

Correct answer: B. The gear is down and locked

Three green lights confirm the gear is down and locked, each light being triggered by the down-lock microswitch on its respective leg. A leg that is merely down but not locked will not illuminate its green light, so the greens indicate more than just gear position.

Correct answer: D. Moving at high speeds on the ground.

Shimmy is a rapid, potentially damaging oscillation of a wheel about its vertical axis that develops when moving at high speed on the ground. It is countered by torque links, shimmy dampers and correct tyre pressures.

Correct answer: C. the brake pads overheating

Brake fade occurs when the friction pads overheat: at high temperature the coefficient of friction falls sharply, so braking effectiveness fades away even though pedal pressure is maintained.

Correct answer: D. Multi disc.

Modern transport aircraft use multi-disc brake units, in which alternating rotor and stator discs are squeezed together by hydraulic pistons. Multiple friction surfaces provide the large braking capacity needed in a compact wheel space.