What is the maximum RPM of the compressor/turbine in an APU?

The correct answer highlights that the maximum RPM of the compressor/turbine in an Auxiliary Power Unit (APU) can reach up to 43,000 RPM. This high RPM is essential for the efficient operation of the APU, as it must generate enough compressed air and power to support aircraft systems when the main engines are not running.

APUs are designed to operate within a specific RPM range to ensure optimal performance while maintaining reliability and safety. The 43,000 RPM figure aligns with the typical specifications found in many APUs used in various aircraft, making it an important figure for aircrew to know. Understanding this maximum RPM helps ensure operators can properly assess performance and monitor the system during pre-flight checks, maintenance, and operational procedures.