How is AMAD power supplied during ground maintenance?

• A. By the APU ground maintenance operation.
• B. By the aircraft battery.
• C. By an external power cart.
• D. By the environmental control system.

Answer: (A)

AMAD stands for the Airframe Mounted Accessory Drive. It powers engine accessories when the main engines aren’t running, so on the ground you still need a source to drive those accessories for maintenance tasks.

The APU, when run for ground maintenance, provides that drive. It spins the AMAD, which in turn powers the hydraulic pumps and electrical generators needed for checks and servicing. This allows hydraulic systems, test devices, and avionics that rely on those accessories to function without the main engines running.

Shorter power sources like the aircraft battery only supply limited electrical power and cannot drive the AMAD. An external power cart can furnish electrical power to the aircraft, but it does not provide the mechanical drive to rotate the AMAD. The environmental control system is powered as part of normal operations and ultimately depends on the AMAD/APU setup for its power during maintenance, but the specific source that drives the AMAD on the ground is the APU being run for ground maintenance.