Aircraft Apu

THE AIRCRAFT APU (Auxiliary Power Unit)

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ABSTRACT
The Auxiliary Power Unit is a system designed to provide a secondary source of energy to a particular plant or craft. In aviation, this system has evolved to become as essential system in today’s commercial transport aircraft. This report provides an analysis of the history, functionality and future development of the aircraft Auxiliary Power Unit. It covers the technological evolution of the APU with reference to specific makes and models, and their direct impact on the aviation industry. The report also details the main components of Auxiliary Power Units, and highlights their impact on the aircraft’s flight controls. The report concludes with a summary of the impact of APU’s on global aviation, and their development into the future.

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CONTENTS

TITLIE PAGE ABSTRACT CONTENTS HISTORY APU SYSTEM COMPONENTS AND FUNCTIONS APU REDUNDANCIES - The RAT FUTURE APU SYSTEMS – The Fuel Cell SUMMARY REFERENCES

1 2 3 4 7 10 11 12 13

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HISTORY
The development of an aircraft Auxiliary Power Unit was first undertaken by British aircraft designer and manufacturer Noel Pemberton Billing in 1916 (Andrews & Morgan, 1987). His P.B.31.E prototype “Nighthawk”, was a quadruplane designed to hunt German airships at night during WW1. For that purpose, it was equipped with a nose-mounted searchlight powered by a 5 horsepower, 2stroke gasoline piston engine, courtesy of the All British Engine Company (ABC) (Andrews & Morgan, 1987). Although the Nighthawk never entered service, it has achieved historical significance as the first ever example of an APU equipped aircraft.
Fig 1: Early ABC APU (ABC and other aero auxiliary engines , 2002)

During WW2, the All British Engine Company once again took up manufacturing of APU systems for military aircraft. ABC APU’s were installed in a variety of aircraft, primarily providing secondary electrical power to various electronic systems (Andrews & Morgan,

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