INVENTION OF AUTO-GIRO

Taranaki Daily News, 25 September 1928, Page 7

INVENTION OF AUTO-GIRO

CHARACTERISTICS OF MACHINE. The original autogiro invented by Senor Don Juan de la Cierva was taken to England in 1925 at the invitation of the Air Ministry. Experts said of it at the time that some of the desirable characteristics of the helicopter had been obtained. Although the machine depended for its support upon an airscrew rotating in the horizontal plane, it could not be classed as an orthodox helicopter, as it could not rise vertically from the ground and hover stationary in the air. It could, however, in addition to flying, climbing and gliding like an ordinary aeroplane, fly- at very low speeds and descend almost vertically under complete control. The low-speed characteristic would be useful for observation and other military purposes, while the ability to descend steeply would enable the machine to land without difficulty in a comparatively confined space, such as might be available in the centre of a large city or on the deck of an aircraft carrier at sea. A number of demonstration flights were carried out with complete success over Lallan’s Plain, Farnborough, in the presence of the Secreetary of State for Air and other officials, the machine being piloted by the well-known test pilot Captain F. T. Courtney. It consisted of an ordinary Avro fuselage, w-ith a 110 h.p. Le Rhone engine, driving a tractor airscrew in the normal position. The rudder, tail plane and elevator were of the usual Avro design, but the wings were replaced by a large four-bladed airscrew, mounted on ball bearings on an almost vertical shaft, so that it was free to rotate in a horizontal planp. The blades of this airscrew were of symmetrical section and in external appearance similar to that of an ordinary aeroplane wing. They were, however, only lightly braced, so that they were fairly flexible in the vertical plane and were, moreover, hinged at the hub to avoid the transmission of gyroscopic forces to the vertical shaft. This lifting airscrew was not directly driven by the engine in any way. When taking off from the ground, the engine driving the tractor screw was started up and the lifting screw was set in rotation byhand. At the demonstration this was done by men pulling on a rope round a frame carried by the blades. As the machine was moved forward over the ground by the action of the tractor screw, the speed of rotation of the lifting screw increased, owing to the difference in the drags on the blades having their leading and trailing edges, respectively, foremost, until a speed of about 140 revolutions a minute was reached, the estimated speed of the machine over the ground bcieng about 30 miles an hour. The pilot could then raise the machine from the ground by- means of the elevator. Climbing was effected by the combined action of the lifting and tractor screws, and the machine eould be controlled in the vertical plane by the elevator and steered by the rudder similarly to an ordinary- aeroplane. In the course of the demonstratiion flights, the machine rose several times to a height of about 300 ft, making either normal gliding descents or descending very steeply, with the engine cut off in both cases.