Electric-wiring installations in British aircraft

THE increasing use of electrical equipment in modern aircraft has in its train focused attention on the distribution system. The major items of electrical equipment in British aircraft generally are supplied to the aircraft constructor as government-approved items. It will be obvious that their correct functioning depends upon the wiring installation which serves them. The size, shape, and equipment layout of an airplane does not lend itself readily to an orderly and well-spaced electric installation. The concentration into certain relatively small areas, peculiar in shape, of a large number of electrical items concerned with navigation, control, offense, and defense, is inevitable and constitutes a major problem for the designer. It is perhaps difficult to appreciate that in a modern four-engined bomber, some 4 1/2 miles of single-core electric cable would be required and in a fully equipped two-engined aircraft, 2 1/2 miles would be used. The problem of accommodation and efficient installation of this amount of wiring demands careful thought and planning. It is unfortunate that even up to the present day too little thought has been given to providing an orderly and well-engineered wiring installation and to ensuring well-protected cable routes. The impression still persists in some quarters that electric cables, being flexible, can be moved and disturbed at will to give pride of place to other more clamorous demands. This has resulted in wiring being “slung in” and is responsible for a high percentage of electric failures directly attributable to faulty location of wiring and equipment in situations where ingress of moisture, mechanical damage by air crew, and deterioration by extreme heat all have made their contributions. The Ministry of Aircraft Production, Directorate of Technical Development, now has specified design requirements in this connection which should mitigate, if not entirely overcome, such trouble in future installations.