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Aviation History
1958
1958 - 0359.PDF
FLIGHT, 21 March 1958 375 Helicopters of the World ... have the distinct advantage of individualinterchangeability instead of requiring replacement of a complete set of blades iforae has become damaged. The blades can be folded backwards to reduce storagespace of the helicopter. • Rotor diam., 53ft; fuselage length, 42ft; weight equipped (Leonides Major), 5,336 lb; gross weight (Leonides Major), 7,800 lb; max. permissible speed, 110 m.p.h.; max. cruising speed (Leonides Major), 99 m.p.h. Wessex The Wessex has beendeveloped initially for naval use and is powered by a Napier Gazelle free turbineunit. Its naval duties include anti-sub- marine operation, rescue, communicationsand casualty evacuation, and a secondary military version will carry fully equippedtroops with alternative accommodation for stretchers. For civil use the Wessex willbe offered as a 12-seater. The airframe is of stressed-skin con-struction and the tail and the fuselage is arranged to fold, thereby saving 8ft ofhangar space. The tail rotor driving shaft disengages automatically and folds withthe tail unit. Volume of the main cabin is 397 cu ft, and access is by sliding doors—4ft high by 4ft 4in wide—on the starboard side. A hydraulically powered winch hoistis fitted above the cabin door on the star- board side of the helicopter. Loads of600 lb can be lifted. Control is either by the pilot or the crewman in the cabin. Access to the engine compartment, inthe nose, is by downward-hinging doors, as distinct from the conventional hori-zontal-opening clamshell doors fitted to prototypes. The doors are also service plat-forms for radio and electrical gear in com- partments in front of cockpit. Dual controlsare provided and there are two indepen- dent high-pressure hydraulic servo systemsoperating on both the azimuth and collec- tive pitch controls. A spring-loaded stick-centring device neutralizes stick forces for any set flight condition. The rudder (tailrotor) control is also servo-operated. Standard fuel capacity of both civil andmilitary versions is 300 Imp. gal, disposed in ten crash-proof bag tanks in the bellystructure of the fuselage section beneath the cabin floor and one big tank in aforward section of the belly space. The four all-metal main rotor blades areof similar construction to those of the Whirlwind, retaining the Westland trailingedge "pocket" construction. The rotor hub is of similar design to that proved in theWhirlwind, incorporating flapping and drag hinges with appropriate dampers andswash-plate control mechanism. By fold- ing the blades manually towards the rearthe overall length of the machine can be reduced from 57ft 3in (minimum positionof rotor) to 38ft 2in. Because of the free turbine characteris-tics it has been possible to eliminate the conventional clutch and fan unit thussimplifying the transmission and saving weight. The epicyclic main gear box nowhas only a single reduction stage which materially contributes to improve strengthand mechanical functioning of this unit. The production version of the Wessexwill have a Napier Gazelle NGa.13 engine, having a 1 hr rating of 1,430 s.h.p. and amax, continuous rating of 1,200 s.h.p. As the free-turbine system eliminates allmechanical linkage between the turbo compressor and the rotor drive, the enginecan be run, with the rotor braked, under no-load conditions up to ground idlingspeed. The makers claim that flight trials have proved the Wessex to be the quietestrotary-engined machine so far developed. Omnipol HC-2 H el i-Baby. • Rotor diam., 56ft; overall length, 65ft 9in;empty weight (transport), 7,600 lb; gross weight, 12,600 lb; cruising speed, 115 m.p.h.;max. speed, over 132 m.p.h.; hovering endur- ance, 3 hr; vertical rate of climb at s.l., 600ft/min; max. range, 340 n.m. (standard tankage). Westminster The first example of thisvery impressive twin-turbine helicopter (Napier Elands) is a "crane" or utility ver-sion, and it is expected that this machine will begin its engine runs about May. Thetype will later be developed for civil and military transport. Of Westland design, the Westminsterwill utilize some components of the Sikorsky S-56. The two Napier Elandshave rear drive and because of this feature they are placed well within the fuselagecontours, thus, the makers point out, mini- mizing rotor downwash interferenceeffects and providing a configuration with optimum hovering performance. Themakers further state that the use of S-56 components such as the main rotor bladesand hub, tail rotor, tail rotor transmission, the epicyclic gearing and other details inthe main rotor gearbox—also the dupli- cated power-operated flying controls—means that full advantage is taken of the lead time gained by these American-designed components. Together with these advantages there are the benefits oftesting and proving which the American components have had over a considerableperiod of operational conditions. The prototype will be powered byEland 229 engines of limited power out- put, but all components of the helicopter,such as the rotor transmission, rotor head, etc., have been designed to accept thepower of the more powerful Eland NE1.5 engines which will be available for produc-tion helicopters. These engines, it is remarked, will confer a remarkable degreeof safety to the operation, since the power of the Eland NE1.5 engine is sufficient forsingle-engine hovering flight. The rotor hub is of Sikorsky design. Alarge offset of the flapping hinge provides a e.g. range of 24in, which permits indis-criminate loading without the usual neces- sity for ballasting. All-metal main rotorblades with heavy extruded leading-edge spars and honeycomb-filled trailing areasafford freedom from incidental damage and a fatigue life of over 2,000 hr. Provision ismade for hot air de-icing of both the main and tail rotor blade assemblies. The fuselage is of monocoque construc-tion with provision for a normal fuel load of 920 Imp. gal of fuel under the cabinfloor. The floor structure is designed to accommodate seat rails and the dispositionof large windows permits a variety of seat- ing arrangements. The simple fixed undercarriage, withlow-pressure tyres, is suitable for operat- ing from unprepared ground. At a cruisingspeed of 150 m.p.h. range performance is not unduly affected and maintenance pro- cedures are materially improved by itsbeing non-retractable. Provision is made in the transport ver-sion for at least 39 passengers. • Rotor diam., 72ft; overall length, 86ft 9in;empty weight equipped (civil), 20,000 lb; nor- mal gross weight, 33,000 1b; estimated cruisingspeed, 150 m.p.h.; estimated rate of climb at s.l. (two engines at 66 per cent max. cont.power), over 2,000ft/min; still-air range (full normal fuel), 500 miles. CZECHOSLOVAKIA Omnipol, Ltd. Washingtonova 11, Prague III.HC-2 Heli-Baby The following is a maker's description of the HC-2 Heli-Baby: "The Heli-Baby is the world's light- est two-seater helicopter with a three-bladed, fully articulated main rotor and dual controls. The powerplant is a flat-four Praga DH developing 83 h.p. at 3,000 r.p.m. "The Heli-Baby can be used as a trainer,observation post, courier and for a number of other jobs. The following features makeit well suited for primary helicopter pilot training: rugged construction, controlswith suitable response and sensitivity, satisfactory stability characteristics and lowcosts per flying hour. Practice engine-off landings can be performed without thenecessity of switching off the engine. The Heli-Baby has an extremely low vibrationand noise level, and an excellent visi- bility. Its small overall dimensions andhigh manoeuvrability enable the Heli-Baby to land on and take off from the smallestunprepared sites. As a single-seater, the Heli-Baby can be profitably used fornumerous other purposes, such as air-mail service, advertising, agricultural pest con-trol, field intensity surveys, fire patrol, material transportation, snow and ice sur-veys, etc. Besides the pilot, the Heli-Baby can carry a photographer, reporter, geolo-gist, doctor or any other person needed urgently anywhere. "In all these operations the Heli-Babyis unsurpassed in economy, as it carries a pilot and a total of 220 lb of payload overa distance of 62 miles in a one-hour flight at a total consumption of 4.85 gal of fuel.Over long distances it can be easily trans- ported on railroad or truck, due to its lowweight, small overall dimensions and quickly removable rotor blades. Thegeneral layout of the Heli-Baby makes it possible to inspect and service the wholemachine from ground level." • Rotor diam., 28ft llin; overall length,34ft Sin; empty weight, 840 lb; gross weight, 1.280 lb; max. level speed, 78 m.p.h.; cruisingspeed, 62 m.p.h.; range at cruising speed, 93 miles: hovering ceiling (with ground effect),3,600ft; service ceiling, 10,150ft; rate of climb, 710ft/min.
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