L-1011 APU: APU Application (49-11)

Flow of pneumatic air from the APU load compressor can be monitored and controlled at the Flight Engineer's Engine Bleed Control Panel. Duct pressure may be monitored on the duct pressure indicators.

As can be seen from the panel schematic, APU pneumatic air is available for engine starting, ATM operation, or air conditioning pack operation. APU air is never mixed with air from another source to prevent damage to the APU.