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Aviation History
1956
1956 - 1051.PDF
FLIGHT, 3 August 1956 If? SEEN AT ST. YAN Notes on Sailplanes and Equipment at the World Gliding Championships (Left) The German Ka2B Rhbnschwalbe, with swept - forward wing. This machine was entered by Tur- key in the two-seater class at St. Yan. IT is not at all certain that the pilot of the most efficient sailplanewill be the winner of a championship. Other factors such aspiloting skill, weather and luck are as important. Nevertheless, the fact is that the majority of the sailplanes seen at this year'sWorld Gliding Championships in France were quite new since the 1954 Championships, and several other types had beenmodified since then. Many were prototypes and unlikely to go into production, but most designers were presumably hoping thattheir machines would seem to be worth their cost. High performance demands high aspect-ratio and light weight.High performance at low speeds and while circling is not com- patible with low sinking speeds at top speeds unless flaps orjettisonable ballast are employed. Safe landings and very low drag can both be obtained only by retractable wheels or skids.Many sailplanes aiming at very high performance thus tend to become expensive in comparison with the "classical" designscommon in Great Britain. The four British designs (Sky, Skylark 3, Olympia IV and T.42)were very successful. They are of wood and fabric construction and, aerodynamically, have progressed from the twenty-year-oldOlympia only in general cleanness and (on the Skylark, Olympia IV and T.42) in changing the wing profile to a laminar-flowsection. They already cost well over £1,000 which, in a gliding movement which receives no subsidy, is quite enough to haveto pay. At the other extreme, we have sailplanes like the YugoslavMeteor. This was designed by Obad, Cijan and Mazonec and sponsored jointly by the Yugoslav Government and the nationalAero Club. The construction is all-metal, and the magnificent wing finish indicates the use of large and expensive jigs. Thelarge landing wheel is retractable, as is the front skid. The Meteor wing-section is laminar, 16J per cent thick with alj deg washout, and is disturbed only by dive brakes fitted well towards the trailing edge and by full-span flaps of small chord.The chord of the flap proper varies from four to six inches and of the aileron from six to nine inches. The basic wing-section isslightly cambered, but a downward flap deflection increases the camber for circling and for landing. For very-high-speed flying,even the basic camber leads to high drag, and a small upward deflection is used to improve performance. The elevator andrudder both have horn balances, and longitudinal trimming is obtained by a variable incidence tailplane. Two Meteor prototypeshave been built, and the measured performance shows a maximum gliding-ratio of more than 40. The cost, however, is at least threetimes that of the British machines. Two sailplanes which performed well were the Polish-builtJaskolka single-seaters and Bocian two-seater. These have many expensive devices such as flaps, slotted ailerons, sliding hoods,retractable wheels, water-ballast tanks—and even navigation lights and static-discharge wicks! Nevertheless, the price of the single-seat Jaskolka is quoted as only £1,250—kept low, perhaps, by Exotic front-ends: (top to bottom) the Jugoslav Meteor; the Polish Jaskolka Z and the Czechoslovak VSM.40 Demant, both fitted with sliding canopies; and the Hungarian Z.08.
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