Almost all the long-range civil transport aircraft entering service during the next few years will be equipped with some form of instrument system. It is proposed to describe here some aspects of the developments which have been embodied in one such system, the Smiths Flight System, and to indicate its scope when applied to the operation of such aircraft.

Since the war the operation of a high-performance transport aircraft on congested and competitive routes has become an increasingly complicated process. With the advent of the gas turbine, cruising speeds have doubled, and at the same time there has been a tendency towards higher standards of economy and safety. The development of the air traffic control system has brought about a demand for greater precision in navigation, and in the most congested areas by far the greatest number of flights are conducted under instrument conditions. Meanwhile, aircraft have also become more complex, and the pilots themselves are often expected to monitor the operation of the controls and instrumentation associated with the engines, electrics and pressurization as well as carry out the navigation. This extra work has had to be undertaken without any relaxation of the general vigilance which constitutes good airmanship.