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Aviation History
1948
1948 - 1474.PDF
3io FLIGHT September gth, 1948 C>erva Air Horse. Crew of three and 24 passenger intended for training helicopter pilots, it will also have itsmilitary applications, and the low price should appeal to quite a number of private owners. The Skeeter has a single three-bladed main rotor of 29ft dia-meter, and the empty weight is in the neighbourhood of 800 lb. At a normal all-up weight of 1,210 lb, the cruising speed isexpected to be about 75 m.p.h. The engine will be of no h.p., probably a Jameson. Falrey /AUTWARDLY the Fairey Gyrodyne differs from other single-V/ rotor helicopters in that its torque-compensating airscrew is placed on the right wing stub, thus additionally contributingmuch to forward propulsion at forward speeds. This reduces the stresses in the main transmission, but the arrangement alsohas the added advantage that the main rotor is at relatively low pitch, so that the tendency to tip-stalling at high forwardspeeds is reduced. Dr. J. A. J. Bennett, in charge of Fairey's helicopterdivision, was long associated with the late Senor de la Cierva, and in the Gyrodyne he has retained the tilting head of theAutogiro, thereby avoiding the many levers and bearings associated with cyclic pitch control. Blade pitch bearingsare eliminated, and collective pitch change is effected auto- matically about the flapping and drag articulations, the flap-ping hinges being inclined at an angle of about 60 deg in relation to the blade axes at zero torque. When torque isapplied, this angle increases to a maximum of about 70 deg. The Gyrodyne carries pilot and three passengers, with anAlvis Leonides engine. The prototype has a steel tube fuselage, but production machines will have a metal monocoque. Thethree-bladed rotor has a diameter of 52ft, the blades,,being of composite construction, with steel tube spars and wooden ribsand covering. When carrying full load, the all-up weight is 4,800 lb, and as for performance, it is sufficient to recall thatS/L. Arkell established a world's speed record, homologated by the F.A.I., of 124.3 ni.p.h. Firth BASED on Landgraf patents, the FH/01/4 Atlantic type ofhelicopter, two of whiGh are now being built by Firth Helicopters, Ltd., is a twin-rotor, twin-engined machine. Therotors are of the rigid, non-articulated type, in which the equivalent of pitch change is achieved by trailing-edge flaps. Another unusual feature is the transmission from engines torotors. Instead of the usual shaft transmission, use is made of tension rods attached to slanting discs. Irvin-Bell THE Bell 47B, sales rights of which are held by Irvin-BellHelicopter Sales, Ltd., is a small two-seater single-rotor helicopter, in which the two-bladed rotor is of the see-saw type.That is to say the blades have no flapping hinges but tilt around a central hinge, one blade rising as the other is falling. Thereis cyclic pitch control, and the gyroscopic effect of a stabilizing bar gives the machine a good deal of automatic stability. Theall-up weight is 2,100 lb, and the engine is a Franklin flat-six. The maximum permissible speed is 92 m.p.h. Westland - Sikorsky TGOR SIKORSKY is the American designer who has had most-*- experience in helicopter work, and it was therefore natural that Westland Aircraft Ltd., should choose his S-51 for con-struction in England. It is now in production at Yeovil, with an Alvis Leonides engine mounted horizontally. In most otherrespects the machine is identical with its American prototype.' It carries pilot and three passengers at a gross weight of5,100 1b. The rotor head shows the usual flapping and drag hinges, and control is by collective and cyclic pitch sticks, andpedals for controlling the pitch of the tail airscrew. Composite rotor-blade construction is used, the tubular sparbeing step-tapered and the rest of the structure comprising wood ribs with a wood covering over the front 60 per cent ofthe chord. The trailing-edge portion is covered with two thicknesses of fabric. It is probable that later versions willhave metal blades. The Westland-Sikorsky has already done good work in thiscountry, such as experimental mail-carrying and, in real earnest, delivering supplies to the crew of a lighthouse when badweather prevented boats from taking the supplies to the light- house. It has also been employed for pest destruction withgood success. Cruising speed of the S-51 is 85 m.p.h., but what gives abetter indication of its capabilities is the fact that its service ceiling (with forward speed) is 14,000ft, and its hovering ceiling,outside, the ground effect, is 5,100ft.
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