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Aviation History
1941
1941 - 2178.PDF
FLIGHT SEPTEMBER I8TH, TQ4I. THE SPERRY FLIGHTRAY Co-ordinating the Indications of Navigating Instruments THE demand for simplification ot the flight indica-tions which a pilot receives from his instrumentboard is increasing. Indicators and control devices, knobs, dials and lights, have become so numerous in the last five years that they completely cover the instrument panel, walls and roof of the cockpit of multi-engine craft and impose an excessive and confusing burden on the eyes and brain of the pilot. Many efforts have been, and are still being, made to correct this condition by substituting automatic controls for manual wherever possible, the carburettor being a notable example, and by combining the indications of a number of instruments in a single multiple indicator. It is recognised that, to the maximum extent possible, the pilot must be relieved of the necessity of continuously watching a multiplicity of instruments indicating the functioning of engines, airscrews, fuel supply and other elements of the mechanism so that he can devote his attention to flying. So on large landplanes and flying boats carrying a crew of three or four members the responsibility is divided among them, the pilot watching the flight instruments and maintaining the course, altitude and speed, the engineer devoting his attention to the engine instruments and controls, and a navigator attend- ing the navigational instruments and the radio, unless a radio operator also is carried. For convenience the various instruments and controls are grouped together as well as possible according to such a division of related functions. Most instruments needed for safe and accurate fying of aircraft having been provided, the Sperry Gyroscope Co. felt some years ago that considera tion of the arrangement and simplifi- cation of the instrument indications was important, and therefore under- took studies and experimental work to co-ordinate the flight instruments. The object was to provide '' a single indicating instrument which will show on its face all necessary flight informa tion in the most easily interpreted manner.'' Cathode Ray Tube An account of this work has been given to the Institute of Aeronautical Sciences by Preston R. Bassett, vice- president and chief engineer, and Joseph Lyman, senior project en- gineer, of the Sperry Gyroscope Co. Four years of continual experimenting and testing were devoted to the prob- lem, and, although the work is still unfinished, enough has been accom- plished to prove that the method of indication has great value for scheduled flying and for instrument landing. The Sperry instrument has been given the name Flightray, because of The Sperry Flightray installed forexperimental testing in the instrument panel of a United Air Lines twin-engine Boeing 247 transport used as a flight research laboratory. (Howmany controls, dials, knobs, levers and lights can you count ? We makeit 50, and there are more that cannot be seen.) employment in it of the cathode ray for giving a combina- tion of visible indications on a single small face. The photograph shows the face of the instrument, which is a fluorescent screen on which a variety of luminous patterns can be drawn. This is the screen of a cathode- ray tube. For those who are not familiar with the cathode-ray tube it may be said that this piece ot apparatus works by the impact oi a beam of electrons on to a glass screen covered with a substance which fluoresces (or, more simply, glows with a soft green light) under the influence of the electrons. When undeflected the beam produces a stationary bright spot on the screen, but it may be made to draw any desired pattern, such as straight horizontal or vertical lines or a small circle, by applying an alter- nating current to either vertical or horizontal deflection plates in correct phase relationship so as to cause the luminous spot to travel in straight lines or to describe a circle. • Electrical Details The 2,000-volt direct current required by the tube is obtained by driving a small dynamotor from the 12-volt or 24-volt battery of the aircraft and transforming and rectifying the alternating current delivered by the dyna- motor to direct current for operation of the cathode-ray tube. The same machine supplies direct current for the amplifiers used. The total power requirements have been reduced progressively from 240 to less than 100 watts.
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