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Aviation History
1949
1949 - 0670.PDF
454 FLIGHT gress in the helicopter field, this country can more than hold its own. It is worth remembering that one of our American contemporaries recently admonished its readers not to forget that they could still learn something from this country's helicopter work. Perhaps the most spec- tacular of British helicopter achievements was made with the aircraft which forms the subject of this article, the Fairey Gyrodyne, for on June 28th, 1948, in the hands of S/L. Basil Arkell, this aircraft established a new world's helicopter speed record at 124.3 na.p.h. In relation to this and the foregoing remarks about official support, it is all the more noteworthy to emphasize that this aircraft is a private venture by the Fairey Aviation Co., Ltd. Fairey Gyrodyne Lateral section through distribution gearbox and transmission to the side airscrew, showing flexible couplings, bearing assemblies and cardan shaft details basically a braced-trusswork welded-skeleton of steel tubes to which the enclosing skin is applied in the form of panels, virtually all of which can be removed for accessi- bility. It is, however, planned to employ a monocoque structure for production versions of the aircraft. The wings are semi-monocoque structures, built up with two spars of extruded T-section booms and plate webs with pressed sheet chordal ribs and a single wrapped skin for- ward of the rear spar, the trailing edge being a separate sub-assemibly. This relatively stiff structure is necessi- tated to cater for the thrust, drag and inertia loads of the offset airscrew to starboard and, of course, the drag and inertia loads of the complementary battery housing to -AIRSCREW GEARBOX BALL STEADY-BEARWG As a conception, the Gyrodyne originated just before the war to meet a naval requirement for a rotary-wing aircraft capable of operating from the deck of a ship, but owing to war's own exigencies, it was not until 1946 that develop- ment of the type really started. It should, perhaps, be explained that the fundamental principle of operation exploited in the Gyrodyne differs from the basic form used in other helicopters. The immediate difference is discern- ible in the use of an offset tractor airscrew instead of the lateral thrust airscrew carried on a tail boom in other types of single-rotor helicopter as a means of compensat- ing torque reaction. Usually, the power distribution is to provide a maximum for the main lifting rotor and a minimum for the balancing rotor, but in the Gyrodyne, par contra, the power given to the main rotor is kept as low as possible and the remainder utilized for the credit purpose of forward propulsion. Although a subsidiary quality of uniqueness in helicopter practice, the use of stub wings and of horizontal and ver- tical tail surfaces results in the Gyrodyne having a stable fuselage. The compactness of the aircraft belies, at first, the generous accommodation: forward of the leading edge of the "wings," the fuselage is wholly cabin. A useful idea of the degree of spaciousness is given by our cut- away drawing, and although some measure of the quality of appointment is also conveyed, the air of quiet com- fort and unostentatious luxury which wraps about the traveller by Gyrodyne is something only to be appreciated by actual experience. On the score of capacity, perhaps one of the most useful forms which the Gyrodyne is likely to take is that of an ambulance. Two full-size stretchers can be accommodated, one above the other, on the star- board side of the cabin, access being afforded by splitting the nose on the vertical centre-line and hinging the star- board half to swing away. A seat is provided for a nursing orderly behind the pilot and adjacent to the heads of the stretchers. The level attitude of the Gyrodyne in flight is a further advantage in this instance. Structurally, the fuselage of the Gyrodyne Mk. I is port. Again, the existence of these strong appendages offered a first-class opportunity to provide the aircraft with a wide track undercarriage (10ft). Each of the oleo pneu- matic telescopic struts—of Fairey manufacture—is anchored in a light alloy block through-bolted to extra-heavy chordal ribs, the head of the leg piercing the block core, which is countersunk top and bottom to provide seatings for annular cones on the leg, squeezed up by a ring nut threaded on the strut crown. A similar form is adopted for the nose- wheel strut which, incidentally, is furnished with a twin- track electrical conducting tyre. Leg travel is 12m for the main units and ioin for the nose unit, the undercarriage being designed to cater for a vertical velocity of 12ft/sec. Tail Surfaces A semi-monocoque structural form is also employed for the tail surfaces, but the material here is wood. Two box ribs of spruce booms and ply webs are used in conjunction with built-up chordal ribs and a plywood skin. The booms are continuous and are attached to the rear fuselage with two fork-and-lug fittings from the front spar, and a single- pin attachment at the base of the rear spar to the apex of a two-strut brace running down to the heel ot.the rear fuselage. The fins are of similar construction to the tail- plane and are attached to the ends of the spars with through-bolted machined fittings. The "elevator" is purely a trim tab, used in forward flight to adjust fuselage attitude, but as the rotor characteristics of the Gyrodyne are such that the fuselage is basically level in cftiising flight, the tab is little used. The rudders are not normally • used at all; to all intents and purposes, they are exten- sions of the fin surfaces, but in autorotation, with the tractor airscrew stopped, there is no positive directional control and, therefore, the rudders are available for use in this connection. The Alvis Leonides which is used to power the Gyrodyne is not the helicopter version of that engine. It is the stan- dard "upright" power plant housed with the crankshaft axis on the fore and aft centre-line of the fuselage. The
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