What is the maximum operating altitude for the APU?

The maximum operating altitude for the APU (Auxiliary Power Unit) on the CRJ 200 is determined by the manufacturer's specifications, which outline the operational limits for various systems on the aircraft. In this case, the correct answer is that the APU can operate up to 37,000 feet.

This altitude limit is crucial because it ensures that the APU can provide adequate electrical power and air pressure necessary for starting the engines and maintaining systems when the aircraft is not connected to an external power source. Operating the APU above this altitude could result in insufficient performance, which could compromise operational safety by not meeting the power and pneumatic demands of the aircraft.

The APU's performance is designed around optimal conditions, and exceeding the specified altitude might lead to inadequate thrust, electrical output, or bleed air pressure, which could hinder the aircraft's operational functions. Therefore, understanding this limitation is essential for flight crews to ensure the safe and effective use of the APU during flight operations and ground handling.