AWA aircraft instrument manufacturing during WW2.

Aircraft instruments were not made in Australia before the war, and one of the important tasks of the new industry was to provide ample supplies of these instruments. Their manufacture was spread over three firms. At the works of Amalgamated Wireless (Australasia) Ltd a whole factory was devoted to making compasses, the Sperry gyro horizon, Sperry directional gyro, rate-of-climb indicator, pressure gauges and altimeters. Warburton Franki Ltd of Melbourne concentrated on such equipment as ammeters, voltmeters, and air temperature indicators, while H. A. Chivers of Melbourne made tachometer generators, tachometer indicators and turn-and-bank indicators. In selecting the directional gyro for special mention two considerations have been uppermost: it was then the only device affording fixed directional reference in the cockpit of an aircraft in flight; and its manufacture called for considerable skill.

The instrument was introduced into the manufacturing program at A.W.A. in January 1942. The greatest care had to be exercised in keeping the premises where it was made free from dust. Traditional watch-making anti-dust practices were not good enough; even the type of clothing worn by the employees concerned was carefully regulated. The gyroscopic movement of the instrument had a speed of 11,500 revolutions per minute (an ordinary electric fan made 2,000 a t the most) and being delicately poised could be irreparably damaged if small specks of dust were allowed to enter the pivots or ball races. Operatives were trained to establish by a sense of touch the permissible "play " of 0.0005 of an inch in dynamically balancing the unit. The permissible THE AIRCRAFT INDUSTRY 393 machining tolerance in making the parts of the gyroscope was one ten - thousandth of an inch. Difficulties caused by the unusual features of its castings held up production for several months, but by September 1942 the target of 30 instruments a week was reached. A.W.A's contract ended in May 1945, by which time more than 2,000 instruments had been made.

Coupled with the directional gyro was the gyro-horizon, a device which created for pilots an artificial horizon so that the orientation of an aircraft with respect to the earth's horizon could be indicated accurately without the earth's horizon being visible. Like the directional gyro it consisted of a spinning wheel (15,000 revolutions a minute) supported by gimbals, but it was also fitted with a pendulum and vanes which automatically corrected any drift error caused by friction in the bearings. More than 2,000 of these instruments were made.

The Aircraft Industry Soon after the war, Ch 18, Page 392 & 393

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