_______ brakes are used in the wheels of large jet-transport aircraft.

• A. Single-disc
• B. Dual-disc
• C. Twin-disc
• D. Multiple-disc

Answer: (D)

When stopping a large jet, the brakes must absorb a huge amount of energy and do it without fading from heat. That requires a brake design with a lot of friction surface and plenty of heat-dissipation capacity. Multiple-disc brakes achieve this by stacking several friction discs in each brake unit, with spacers and hydraulic pressure compressing the stack so all the discs share the load. This arrangement greatly increases the available torque and allows heat to be spread across many discs and carried away by the cooling airflow, which is essential during repeated or hard landings.

Single-disc or only a couple of discs wouldn’t provide enough surface area or heat capacity for the energy of a large jet, so they are more prone to overheating and reduced braking effectiveness. The term multiple-disc captures the needed high-energy, high-heat-performance requirement of brakes on large jet-transport aircraft.