Which statement best describes cross-bleed starting with an APU?

Which statement best describes cross-bleed starting with an APU?

• A. It powers hydraulic systems
• B. It supplies electrical power to engines
• C. The APU provides conditioned bleed air at sufficient pressure/temperature to facilitate starting other engines via cross-bleed lines
• D. It is used only for cabin air

Answer: (C)

Cross-bleed starting with an APU relies on using the APU’s conditioned bleed air at the right pressure and temperature to drive the air turbine starter of another engine through cross-bleed lines. This pneumatic power spins the target engine up to idle so it can take over and run on its own. It’s a way to start engines without external air sources or using the engine’s own bleed air for the start, and it isn’t about hydraulics or electrical power for the engines. It also isn’t limited to cabin air; bleed air is specifically used for starting via the cross-bleed path.

Cross-bleed starting with an APU relies on using the APU’s conditioned bleed air at the right pressure and temperature to drive the air turbine starter of another engine through cross-bleed lines. This pneumatic power spins the target engine up to idle so it can take over and run on its own. It’s a way to start engines without external air sources or using the engine’s own bleed air for the start, and it isn’t about hydraulics or electrical power for the engines. It also isn’t limited to cabin air; bleed air is specifically used for starting via the cross-bleed path.