Is it allowed to use the APU bleed and HP cart simultaneously?

Using the APU bleed and HP cart simultaneously is prohibited due to safety and operational considerations. Operating both systems at the same time can lead to various issues, including potential over-pressurization or strain on the aircraft’s pneumatic system.

The APU (Auxiliary Power Unit) provides bleed air which is essential for engine starting and supplying air for various pneumatic needs during ground operations. The HP (High Pressure) cart is an external air source used to supply bleed air for similar needs. If both air sources are engaged at once, it could cause conflicting pressures and reduction in system reliability, ultimately endangering ground crew and the aircraft's operational integrity.

It is crucial for pilots and crew members to adhere to these regulations to ensure safety, maintain proper aircraft operation, and extend the life of the equipment used in ground support operations. Understanding this aspect of ground operations is essential for ensuring compliance with safety protocols and the effective functioning of aircraft systems.