A Novel Start System for an Aircraft Auxiliary Power Unit

This paper describes the design and the main technical characteristics of a new Start System for an Aircraft Auxiliary Power Unit (APU). The system eliminates the one battery, dedicated for APU starting, the DC Starter and its Clutch Assembly, by driving the generator installed on the APU as a motor to achieve the start. This new system extends the APU life by providing a faster start, assisting the APU acceleration up to 8,400 rpm and maintaining lower engine temperatures during start. The battery voltage control feature and the option of using AC power for start, to save battery power and extend battery's life is another advantage over the classical DC.