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Aviation History
1945
1945 - 1219.PDF
JUNE 2IST, 1945 FLIGHT By filming the aircraft through a grid of wires, take-off run, acceleration and rate-of-climb can be accurately measured. Simple Performance Testing H,ow the Ranger Aircraft Engine Firm Determines Take-offs, / Climbs, Qlides and Landing Runs OMPLETE performance testing of aircraft is a com- plicated business, as those will agree who heard Mr. E. T. Jones lecture on the subject to the Royal Aeronautical Society in February of last year, or who have since read his paper in the R.Ae.S. Journal. Few, if any, private companies could afford the expense of the necessary equipment, not to mention the considerable personnel required to carry out the tests. Such work is, therefore, left to Government establishments specially equipped and staffed for the purpose. There are certain aspects of performanc&fhowever, for which tests at the manufacturer's airfield are fre- quently required, and the equipment for Which need Jiot be either expensive or complicated. Take-off and ing runs can be measured with a tape on me grounc these distances do not always, by themselvVs>tgiv^a'll the information needed. Angles of glide during an approach, speed of glide and distance run from touchdown to stand- still, give a much more complete picture. Or, again, with the take-off run it may be desired to couple accelera- tion up to the moment of "unsticking," and speed and angle of climb from that point onwards, as far as the clearing of an obstacle of given height. A very simple technique for obtaining an accurate record of such tests has been evolved by the Ranger Aircraft Engines division of the FaiTchild Engine and Airplane Corporation. The outfit merely comprises a motion-picture camera and a wire screen grid. The f camera, a BqJex coupled to an intervolometer set, is placed five fefet from the screen. It is set to take four frames per second. The wire icreen grid is ioft. long and 30m. high, and the mesh, ax spacing of the wires, is i.2in., so that there are 100 squares in the length of the screen and 25 in the heigh/ Now obviously an aircraft which taxies past the screen on the side opposite to that on which is the e pja«tographed on the film, and if the ^enftbe"/screen and the aircraft is known, will represent a certain distance, screen is placed 1,000ft. away from the camera,/can dist each In t , and each square represents 20ft. of runway, at er the central part of the screen. Similarly, of e, the vertical side of the square represents a height ft'20ft. Camera-plotted Graph It will be seen that by combining the distances ascer- tained from the screen measurements and the fact that four separate pictures are taken every second, it is pos- sible to measure quite accurately such things as accelera- tion and deceleration, in addition to speeds and angles of climb or glide. In fact, the camera plots a graph in which the aircraft itself, or some part of it, forms th«-""""* "dots." For measuring the angle of incidence of the wings in either straight flight or in a climb or glide, a black line is painted on the fuselage of the aircraft. The
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