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Aviation History
1949
1949 - 1805.PDF
FLIGHT, 27 October 1949 569 chief test pilot of the Royal Aircraft Factory, Capt. FrankGoodden, Dr. Thurston said that, initially, two machines were built and flown. The first collapsed in the air after 20 or 30hours' flying and Goodden was killed. The committee of enquiry found that the accident was caused by the airscrewbreaking and fracturing the wing structure. " I didn't believe this," said Ur. Thurston, " and therefore ordered that a guardbe placed upon the wreck and the hole searched and the pieces of the airscrew found and placed together. The whole of theperiphery of the airscrew was found, assembled and photo- graphed. It was obvious that the fracture was not due to theairscrew. I found, however, that one bottom front spar had failed by downward torsion. This could not have happenedunless something else had failed previously in the interior of the wing. I therefore visited the second machine, which had been flown for nine hours, and gave the bottom wing a bangwith my hand. There was a nasty jarring sound from the in- terior bracing, which was evidently slack. I therefore strippedthe fabric with my penknife and incipient lines of failure could be seen in the varnish of the strengthening ribs between thestruts. The structure, in effect, was like a box without a bot- tom. There was no provision to resist torsion due to downloadon the front of the wing, so I suggested that a piece of three- ply should be placed between the upper and bottom ribs andthe front and back spars to take the torsion. This was done and large numbers of this very fine machine were made andflown without further trouble. " By taking advantage of every piece of evidence availablea system of design and testing was evolved which, with slight modifications, has remained in force to the present day." A.T.C. GLIDING NEWS New Two-seat Trainer : Some Soaring for CadetsR ESERVE Command announced last week that it is hoped to provide each of the 49 A.T.C. gliding schools with one Slingsby Sedbergh two-seat trainer by March next year, and that, during 1950, the schools will work to a new, more ambitious programme. The Sedbergh X Mk. T, to use its full designation, is identical with the successful civil two-seat training glider known as the Type 21B, which was designed to provide clubs with a robustly constructed and easily maintained aircraft' of medium performance. Forward of the two main wing-attach- ment frames, the fuselage is of wooden stressed-skin construc- tion, the remainder being of fabric-covered girder type. The braced, 54ft-span wing, mounted on a large faired bulkhead, is of wooden construction, fabric-covered aft of the main spar, and the control surfaces also are fabric-covered. The cockpit, forward of the main bulkhead, has side-by-side seating with dual stick-and-rudder-pedal controls, and offers excellent visibility. Provision is made for the wearing of back- type parachutes, and there are twin "bugs-eye" windscreens to protect the occupants during air-towing. A larger type of full-width windscreen has been found to set up severe turbu- lence. For comfort when acting as passenger, each occupant can rest his feet in a well in the cockpit floor. The Sedbergh has an all-up weight of 590 lb. Its best gliding angle is 1 in 21 at 42 m.p.h., and its minimum sinking speed is 2.8 ft/sec at 38 m.p.h. Over a speed-range of 36-50 m.p.h., the sink remains below 3.75 ft/sec, and the gliding angle does not exceed 1 in 18. Stalling speed is 28 m.p.h. Very few of the A.T.C. schools had the advantage of using a two-seat trainer, and the majority of pupils have been taught the rudiments of gliding—and little more—in single- seat Cadets and Prefects, together with a few non-standard types such as the German Grunau Baby. The advent of the Sedbergh will permit a much higher standard of training to be reached, and will enable the instructors to log more flying hours than were previously possible. The Royal Aero Club's "A" certificate—which entails a straight solo flight of 30 sec—has been the standard reached by the majority of A.T.C. gliding pupils, but during next year those who show sufficient promise will graduate to the solo circuit stage, in which a one-minute-flight qualifies for the "B" certificate. Reserve Command also announces that, in exceptional circumstances and suitable weather, a certain num- ber of cadets will be allowed to qualify for the "C" certificate by making a five-minute soaring flight. r Items of interest in the Sedbergh cockpit are : (I) batteries; (2) quick-release ; (3) A.S.I. ; (4) turn-and-slip indicator ; (S) quick-release knob ; (6) variometer; (7) altimeter; (8) spoiler control lever and lock. New servicing arrangements will be in operation next year, whereby instructors will undertake only minor maintenance duties, while second- and third-line servicing of the gliders will be in the hands of the nearest R.A.F. station, or—where distance is prohibitive*—-an R.A.F. mobile servicing party. There will be improvements in the type of ground equipment issued: new 15-cwt trucks are now being modified for use as retrieving vehicles, and more efficient winches will be in service, giving better launches and greater serviceability. During July, Reserve Command opened its Instructors' Glid- ing School at Detling, where some of the A.T.C.'s 500 instruc- tors are now on preliminary courses. The school is now com- manded by F/L. R. C. Forbes, a well-known sailplane pilot. In 1928, 2,127 cadets reached "A" certificate standard, and by June of this year 1,186 were similarly qualified; an indication of the Corps' enthusiasm is the fact that the demand for glider training has generally exceeded the capacity of the schools. Although the introduction of the Sedbergh and other new equipment may not increase the numbers of cadets trained, the instruc- tion will be more advanced and more useful. Apart from its value as pre- Service training, the new A.T.C. pro- gramme may, by giving its members deeper insight into the art of soaring, strength of the British gliding move- ment. (Left) The civil version of the Sedbergh, the Type 2IB, has given good service to clubs for many months. B 29
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