Auxiliary power unit
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An auxiliary power unit (APU) is a device on a vehicle 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, 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.
A Honeywell GTCP36 APU mounted in the tail of a business jet
The APU exhaust in the tailcone of an Airbus A380
The intake diverter of the Jumo 004, with pullcord starter handle for Riedel APU and its sparkplug access ports
The Riedel 2-stroke engine used as the pioneering example of an APU, to turn over the central shaft of both World War II-era German BMW 003 and Junkers Jumo 004 jet engines (pullcord starter variant shown).
Supermarine Nighthawk
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The Supermarine Nighthawk or P.B.31E was a First World War British aircraft, designed by Noel Pemberton Billing and built at Woolston, Southampton after Pemberton Billing's company became Supermarine Aviation Works Ltd. The P.B.31E, as with its predecessor the P.B.29 "Battle Plane", was an anti-Zeppelin night fighter. It was operated by a crew of three to five, and was designed to fly for 9–18 hours. The prototype of the P.B.31E flew in February 1917. It quickly became obsolete when it was found that Zeppelins could be more easily be destroyed by igniting their hydrogen bags using explosive bullets. Only a prototype aircraft was built.
Supermarine Nighthawk
The Pemberton Billing PB-29 at NRAS Chingford in 1916
The P.B.31E at the Supermarine works at Woolston, Southampton. R.J. Mitchell, who was to succeed as the company's chief designer, is standing fourth from the left.
The Nighthawk propeller at Solent Sky