L-1011 APU: APU Operation and Location (49-3/4)

The APU can be started from sea level to flight level 250 and will operate up to flight level 310.

The APU is installed at the rear of the aircraft below the No. 2 engine "S" duct forward of the No. 2 engine firewall. The APU is contained in a fireproof compartment and the platform the APU is mounted on is part of the aircraft skin.