The auxiliary power unit (APU) is used to start the main engines and for pre-flight preparation of helicopters and aeroplanes. During flight, it serves as an auxiliary source of power if the main engine fails. PBS has been developing and manufacturing turbine power units for over 50 years. During this time, almost 6,000 APUs had been installed. It is one of 4 companies in the world that holds EASA certification for development, production, and maintenance of APU for the aerospace industry.