At what maximum altitude can an APU engine start occur?

The maximum altitude for an APU (Auxiliary Power Unit) engine start in a CRJ 200 is indeed 30,000 feet. However, option D, which states 13,000 feet, refers correctly to the limits for general APU operation.

The APU provides electrical and pneumatic power while the aircraft is on the ground, and starting the APU at high altitudes is limited due to reduced air density and increased demands on the starting system. While the aircraft is capable of starting the APU at this altitude, it is important that operators understand the limitations to avoid any potential issues related to performance and power availability.

When establishing altitude limitations, part of the considerations revolves around the performance capability of the APU at various pressures and temperatures encountered at altitude, making sure it can provide the necessary power without exceeding operational limits or compromising safety. In flight operations, the focus is also on maintaining overall aircraft performance, ensuring that all systems are functioning efficiently.