HOVERING FLIGHT

Greymouth Evening Star, 17 April 1939, Page 12

HOVERING FLIGHT

HELICOPTER TRIALS IN PARISThe most promising of the helicopters, offered years ago to Great Britain and declined after the inventor had been encouraged to transfer his work to London, is now pursuing its course of development in Paris. The first of a series began its flying trials in the yard of a Paris factory, and made hovering flights of 30 minutes’ duration. It is the forerunner of other models calculated to give a fast rate of climb, a high ceiling, and high forward speed’ in combination with the ability to make slow descents through the lift generated by autorotation (says the Aviation Correspondent of “The Times”). The principle applied in these helicopters is that on which the Hungarian inventor, Mr Oscar von Asboth, has been working for more than 10 years. In 1931 an offical of the British Air Ministry flew one of the early models in Budapest, and gave a favourable report of its stability and its power of vertical ascent. In 1936 the Air Ministry purchased the drawings of the invention and contemplated the construction of a helicopter, but various circumstances impeded the plan, and eventually the work was transferred to Paris. There the first machine; fitted with a 180 h.p. engine driving two co-axial lifting airscrews, has flown at a loaded weight of 1,3201 b, and has developed an Initial rate of climb of about 14 feet a second.

SMALL SCREWS. One feature of this helicopter is the small diameter of the lifting screws. It is no more than 16ft 4in. In the next model of similar power the diameter will be increased to 36ft, the loaded weight to 2,2101 b, and the rate of vertical ascent to 29ft a second. This makes an interesting comparison with the Focke-Wulf helicopter, which has rotors of 65ft diameter, and an initial rate of climb of about. Bft a second. In the biggest model he has yet projected, Mr von Asboth'proposes to use screws of only| 55ft diameter, and these, driven by | engines of 2,000 h.p., are estimated to lift 10.0001 b (of which 4,3001 b will be useful load) to 20,000 ft in 9J minutes. This type is estimated to have a top forward speed, obtained by tilting the rotors, of 270 miles an hour. The efficiency of this type of helicopter in lift and stability has been fairly well proved. The claim of efficient autorotation is also made, but the method of securing control in those circumstances has not been revealed. In his earlier models, the inventor made no use of the system of altering the angles of the rotor blades which has ben developed in the Autogiro and in the Focke-Wulf helicopter. Instead, he relied for control on movable surfaces placed in the downwash of the rotors and they proved admirable so long as the engine was running to create the downwash. The condition of descent with engine stopped involves consideration of the control surfaces which apparently no longer have powerful downwash in which to operate.

In none of the models now in use or projected is the rate of autorotational descent to be more than 16ft a second. This would enable forced landings to be made in very small fields, provided sufficient control remained at the service of the pilot to < >i-ible him to chose his landing place. m-.ft’ v . ou sboth ha s dealt with this matter in his new models, they should prove of the utmost importance-