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Aviation History
1963
1963 - 0780.PDF
FLIGHT International, 23 May 1963 751 Double-slotted flaps on the wings and special control surfaces on the nose give the Wren 460 a speed range extending to below 26 m.p.h. (see "Introducing the Wren") S PORT AND B U S I N ESS Introducing the Wren Flight tests have been completed on the Wren 460, a modification of the Cessna 180 designed by Wren Air craft Corporation of Fort Worth to combine normal light-aircraft cruise performance with exceptional low-speed manoeuvrability. The aircraft has been developed as a commercial application of the ULS (ultra low speed) control system recently tested by the US Army on James Robertson's experimental Skyshark aircraft, and is described by the company as the first HTOL (heliport take-off and landing) aeroplane. At gross weight under zero-wind, standard- atmosphere, sea-level conditions the aircraft is stated to take off in under 300ft and land in less than 200ft—well within the 400ft dimension suggested by the Federal Aviation Agency for heliports. The level-flight speed range quoted for the Wren 460 is from under 26 m.p.h. to over 160 m.p.h. The slow-speed performance stems from full-span, double-slotted flaps which can be lowered to one of four positions (15°, 35°, 45°, and 60"). At the fully extended 60° position the lift of the wing is almost tripled and the drag is quadrupled. The ULS control surfaces, mounted on the nose of the aircraft directly behind the propeller, serve to deflect the slipstream and to produce powerful control forces at low airspeeds. The effective ness of the normal elevators decreases sharply as the speed of the aircraft is reduced, while that of the ULS surfaces increases (as power is increased to offset the drag produced by the extended flaps). On the Army's Skyshark aircraft, ULS nose controls are used to provide control in pitch, yaw and roll. On the Wren 460, which does not fly as slowly as the Skyshark, the normal rudder and ailerons are sufficiently effective so that pitch control is the only ULS control needed. The ULS controls are integral with the elevator controls by a direct push-rod linkage to the control yoke, and they operate in conjunction with the normal elevators at all times. Compared with the elevators the ULS controls are of small area, and so have only limited effect during cruising conditions, when the slipstream is only slightly faster than the airflow over the entire aircraft includ ing the elevators. As the speed of the aircraft decreases and power is applied to maintain slow flight, the ULS controls take a bigger "bite." The Wren 460 incorporates a number of other unusual design features. A set of rotatable "teeth" or spoilers are located ahead of the ailerons on the upper surface of each wing. These are con nected directly to the aileron control linkage, and serve to eliminate the adverse yaw which accompanies large aileron deflections at low speeds. Normally "feathered," the spoilers rotate to provide extra drag when the aileron behind them is deflected upwards. To delay the stall at slow speeds, the full length of the leading edge of the wing has been "augmented" by a wrap-around cuff of sheet metal which enlarges the radius of the leading edge and causes a slight "drooping" appearance in cross-section. Stalls are reported to be extremely gentle. The height of the rudder and fin has been increased by eleven inches. The only change in the cockpit is the addition of an LSI, or low speed indicator, driven from an anemometer mounted on the starboard wing strut. The company report that the only ad verse effect of the addition of the new devices is a decrease of approximately four per cent in the high-speed capabilities of the aircraft. Production versions of the Wren will use new production Cessna 180/182 airframes; the power unit is a Continental O-470-R rated at 230 h.p. at 2,600 r.p.m., driving an 82in diameter constant- speed propeller. At a gross weight of 2,8001b, the aircraft carries four people and cruises at 153 m.p.h. at 75 per cent power at 6,500ft. —and the Derringer Illustrated below, the Derringer twin- engined two-seat business aircraft is currently being developed by Wing Aircraft Company of Torrance, California. Powered by two 115 h.p. engines, the prototype Derringer made its first flight in May 1962; production versions, powered by two 150 h.p. Ly- comings, are now under construction at Torrance. Further pro duction is expected to start in Okmulgee, Oklahoma, in 1964. The unusual formula of a twin-engined machine carrying only two people was selected after Wing had carried out surveys which indi cated that more than 57 per cent of all flights in four- to seven-seat aircraft were made with only two people aboard; and that twin- engined types were 1.5 times as active "in trip frequency" as single- engined craft. The Wing Derringer, described above, has a cruising speed of 225 m.p.h. Gross weight is 2,6801b, span is 29ft 2in, and basic price is $27,500 'f
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