What is the APU type used in the ERJ 170/175?

The APU (Auxiliary Power Unit) used in the ERJ 170/175 is indeed the Sundstrand APS 2300. This type of APU is crucial for providing electrical power and bleed air during ground operations and when the main engines are not running. The APS 2300 is tailored for regional jets, making it an efficient choice for the operational needs of the ERJ 170/175.

Understanding the characteristics and capabilities of the APS 2300 helps in grasping the overall functionality and operational efficiency of the aircraft system. This unit provides not only electrical power for starting the engines but also air for cabin conditioning and engine start-up, ensuring that the aircraft can operate effectively even when on the ground without external power sources.

The other options do not apply to the ERJ 170/175, as they represent different models of APUs which are either used in other aircraft or are not suitable for this specific regional jet platform. The correct identification of the APU type is fundamental for maintenance, operational procedures, and understanding the aircraft systems.