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Identifying the inboard wheel half

Aviation Mechanic Airframe (AMA) practice question 10 of 17 on Landing Gear Systems. ACS element AM.II.E.K8 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONWhat distinguishes the inboard half of a modern two-piece aircraft main wheel from the outboard half?

  1. AIt mounts the wheel-spin transducer
  2. BIt drives the brake rotor
  3. CIt contains no wheel bearing cavity
Show the answer and explanation

Correct answer: B. It drives the brake rotor

  • A — incorrect On aircraft with anti-skid brakes the wheel-spin transducer is typically mounted at the capped outer bearing and axle end, on the outboard side.
  • B — correct The inboard half is made to accept and drive the brake rotor, using reinforced keyways, bolted-on steel keys, or bolt provisions, and that brake mounting feature is what identifies it.
  • C — incorrect Both wheel halves contain a bearing cavity that accepts the bearing cup, tapered roller bearing, and grease retainer.

BACKGROUND

Modern aircraft wheels are cast or forged from aluminum or magnesium alloy in two nearly symmetrical halves that bolt together, with a groove at the mating surface for an O-ring because most aircraft use tubeless tires. The two halves are not identical: the inboard half must accept and drive the brake rotors mounted on the main wheels, using tangs fitted into steel reinforced keyways, bolted-on steel keys, or bolt provisions on small aircraft. Both halves have a bearing cavity for the bearing cup, tapered roller bearing, and grease retainer. On high-performance aircraft the inner half often carries thermal plugs with a low melting point alloy core that melts and deflates the tire before heat can cause the assembly to explode. The bead seat area, where the tire contacts the wheel, is typically rolled during manufacture to prestress it.

STUDY TIP

Anchor the inboard half to the brake rotor drive, and remember that the outboard half caps the outer bearing and axle end; nearly every wheel-half question turns on that split.

KEY POINTS

  • The inboard half carries the brake rotor drive feature.
  • The outboard half caps the outer bearing and may serve as a hub cap.
  • Both halves have bearing cavities; the inner half may carry thermal plugs.

SOURCES

  • FAA-H-8083-31B ch13 "Wheel Construction, Inboard Wheel Half"
  • FAA-H-8083-31B ch13 "Outboard Wheel Half"
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MORE ON LANDING GEAR SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.