An auxiliary power unit (APU) is a device on an aircraft that provides energy for functions other than propulsion. They are commonly found on large aircraft and naval ships as well as some large land vehicles. Aircraft APUs generally produce 115 V AC voltage at 400 Hz (rather than 50/60 Hz in mains supply), to run the electrical systems of the aircraft; others can produce 28 V DC voltage . APUs can provide power through single or three-phase systems.
On June 4, 2018, Boeing and Safran announced their 50-50 partnership to design, build and service APUs after regulatory and antitrust clearance in the second half of 2018. Boeing produced several hundred T50/T60 small turboshafts and their derivatives in the early 1960s. Safran produces helicopters and business jets APUs but stopped the large APUs since Labinal exited the APIC joint venture with Sundstrand in 1996.
This could threaten the dominance of Honeywell and United Technologies. Honeywell has a 65% share of the mainliner APU market and is the sole supplier for the A350, the B777 and all single-aisles: the B737 MAX, Airbus A220 (formerly Bombardier CSeries), Comac C919, Irkut MC-21 and A320neo since Airbus eliminated the P&WC APS3200 option. P&WC claims the remaining 35% with the A380, B787 and B747-8.