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Aviation History
1935
1935 - 1572.PDF
SUPPLEMENT FLIGHT. JUNE 27, 1935. I having ascertained the position, both vertically and longi tudinally, of the centre of gravity. Chocks are pulled away and the machine is run round the aerodrome to test the suitability of the undercarriage, brakes, and skid or tail wheel. A special watch is kept for pitching and swing ing ; steering at low speeds may prove difficult and, when the throttle is opened, torque or slipstream may exhibit peculiarities for which remedies must subsequently be sought. The pilot's handling of the machine on the ground becomes increasingly rough, and he subjects it to severe bumping (by picking out a portion of the aerodrome where the surface is bad) and turning. Often, as a result of these taxying tests, a pilot can prophesy any serious vice which the machine is likely to exhibit when taken into the air; this may then be nipped in the bud. On returning to the hangars a detailed inspection is made and, perhaps, detail modifications are called for before the aeroplane first leaves the ground. During the initial tests of seaplanes and flying boats such items as the position of the water line and the stability, riding, airscrew clearance and control on the water must be noted. Now the machine goes out to make its first take-off. At the extreme down-wind end of the aerodrome, with the tail trimming gear in '' half way'' position, the throttle is eased forward and the tail lifts clear of the ground as the machine runs over the aerodrome. In this attitude it is possible for the pilot to feel each control before he lifts the machine off and climbs gradually. It is useful, on the first flight, to throttle back at a safe height and determine the approximate stalling speed, as this will assist in making the first landing, although it is not advis able to stall the machine, as the controls cannot yet be guaranteed to stop a spin. Serious testing of new types is done between 10,000 and 15,000 ft. Turns, of increasing tightness, are made to right and left to test the effectiveness and harmony of the con trols : any vibration is noted and longitudinal stability with engine on and off is tested. Possibly the aircraft will respond well to one or two con trols, but not to the third, showing that the three are not harmon ised, so after the first landing, which, made of course, in a respectful manner, the surfaces may be modified, a larger rudder fitted, or the span of the ailerons increased. The days when wings and tails were in the habit of parting company with the fuselage (one test pilot just could not make up his mind which part to remain with) are passed. It is not un common for a test pilot to stunt a machine on the first flight he makes in it, probably more from exhilaration than any desire to show off. After the completion of the first flight a confer ence is held between the pilot, designer, and chief engineer, and other interested parties, and thef desirability of modifications discussed. Should any be made, the machine, in its new form, is tested " light " once more and then loaded, usually with ballast, to its gross weight. Figures are taken for the machine with varia tions in external drag. For example, a light bomber will probably be tested carrying, say. An Armstrong Whit- worth general - purpose biplane shows her mettle during handling tests. (Flight photograph.)
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