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Aviation History
1948
1948 - 0506.PDF
42O PLIGHT APRIL 15TH, 1948 The SG Mark VI-D Helicopter A Result of Collaboration Between America and Canada The SG Mark VI-D made its first test flight on February I Oth, on the day when it left the shops. THERE is practically no end to the configurations andcombinations possible in the design of a helicopter,but for the moment the anti-torque tail rotor made classic by Igor Sikorsky is a feature shared by most. Into this class falls also the machine which forms the subject of these notes. Superficially, the most notable departure is the use of two superimposed lift rotors which are not, however, contra-rotating. The principle followed is, in fact, exactly that which was familiar to those who remem- ber the early days of flying, when it was not at all unusual to turn a two-bladed airscrew into a four-bladed by simply mounting one close behind the other, with the blades at right angles. That was the easy way. In helicopter work there is no easy way, but the designers of the SG VI-D chose the superimposed rotors in order to facilitate produc- tion by using a repetition of parts, and to get a good compromise between rotor solidity, disc loading and rotor diameter. One of the most remarkable features of the design, and one which is not obvious from mere inspection, is that it is the work of two people only: Mr. Sznycer and Miss Selma Gottlieb, of New York. Between them these two people, who had previously spent two years in theoretical work on rotary-wing problems, prepared the complete aerodynamic -The superimposed rotors have flapping and drag hinges, the former being lozated on the centre line. The mechanism is readily accessible for servicing. SG MARK VI-D HELICOPTER Aircooled Motors 6A4-I45-B3F 5 Gross weight 2,375* Weight empty 1,700 Ib Disposable load ... 675 Ib Rotor diameter 34fc Solidity -044 Rotor speed ;.. 279 r.p.m. Anti-torqu^ rotor diameter 5ft. 2in „ rotor solidity -08 „ rotor speed 1875 r.p.m. Length 30ft. lOin Height 9ft. 3in Track 9ft Disc loading ... 2.62 Ib/sq. ft Power loading 13.35 Ib/h.p. Maximum rate of climb ... ... ... ... ... 850 ft/'min Maximum forward speed ... 90 m.p.h. Cruising speed ... ••• ••- ... •-. 80 m.p.h. and stress analysis, together with all layouts and productiondetail drawings, in about 6,500.engineering hours. The first machine, the SG Mark VI, was designed and built in ayear and a half. It first flew last summer, and to a great extent it proved the rotor vibration and control theories.Detail modifications were introduced in the Mark VI-D, which was designed" and built in the record time of sixmonths. The most obvious change was from a tailwheel to a nosewheel undercarriage. When it came to the problem of obtaining financial .backing, a Canadian company came to the rescue. Under the title Intercity Airlni8j| ofMontreal, this company is presided over by Mr. J. Ernest Saward. The directors are-: J. H.Grundy, Thornton H. J. Curtis, W. S. Hart, Alexis Nihon, R. G. Perry, Roch Tremblay,Jules Timmins, all of Montreal, and Capt. Norman Edgar, of Collingwood, N.J., an Eng-lishman who will be remembered by many from the days when he operated an air line in theWest of England. Treasurer of the company is F. W. Robinson, and the secretary is W. JMarson. The SG Mark VI-D was built and assembledin Montreal, although the engine, rotor blades and certain other parts were made in America.Although it falls in the small helicopter class, being normally a two-seater, it is capable ofcarrying a second passenger, for a range of 120 miles. With pilot and one passenger, the rang^is 300 miles. In the former case, pilot and ont' passenger sit in front, with the second passengerbehind them. Dual controls can be fitted if desired, the instrument panel being directly in
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