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Aviation History
1950
1950 - 1972.PDF
FLIGHT, 23 November 1950 449 It is apparent that the structure of the S.55 has been kept as simple as possible, always with an eye on accessibility and ease of maintenance. Double curvatures and complex structures have been reduced to a minimum, and a good example of accessibility is the enclosure of the nose- mounted engine within two non-structural doors. Gear box, clutch, transmissions and controls are all accessible by the removal of panels, and for example, the fan assembly can be withdrawn through a large door in the fireproof wall of the forward cabin. Access to the main transmission is from the pilots' compartment, and in this instance the removable panels are soundproof. For overhaul, the main rotor head, transmission with accessories and complete hydraulic-servo-control system can, it is claimed, be removed and replaced within three hours. Additionally, every main component can be changed within 15 man-hours. In the supporting structure for the tail cone behind the cabin are the heating and ventilation systems and some baggage space. This compartment is accessible from the outside as well as from the cabin. Interchangeability with die S.51 • A considerable number of the components of the S.55 are basically the same as those in the S.51, and many indi- vidual items are interchangeable. However, the new-type main rotor head is simpler in design, and, it is said, affords more immediate control response and greater stability and manoeuvrability, in addition to an increased centre of gravity travel. Control is by a straightforward mechanical push/ pull system in which friction and vibration are practically eliminated by a servo booster. In the event of an hydraulic failure complete mechanical control remains. The rudder pedals, adjustable in reach, carry individual toe-brakes. An aerofoil surface similar in action to the trim tabs of fixed-wing aircraft and controlled by the pilot from the cockpit, is located behind the tail cone. It helps to main- tain the optimum attitude for the aircraft and gives increased stability. Both main and tail rotor blades are all-metal and should thus need little or no maintenance. The blades in each rotor are interchangeable and those of the main rotor fold for storage or transport. Normal fuel capacity is 150 Imp. gall, sufficient for 400 miles, but for ferrying purposes additional tanks can be fitted which bring the range up to nearly 1,000 miles. In the American military version of the S.55 the Wasp S.1.H2 is fitted to increase performance at the higher alti- tudes. It gives a ceiling improvement of 3,000ft (915 m) as a result of the higher degree of supercharging provided. Details of the rotor head and power hoist may be seen in this photograph. WESTLAND SIKORSKY SJ5 600 h.p. Pratt and Whitney Wasp R-I34O S3HZ) High speed at sea level HO m.p.h. Cruising speed at 70 per cent b.h.p. at 1,000ft (305 m) 86 m.p.h. (177 kmlhr) (138 kmlhr) 1,130 ft/min (5 7 m/sec) 350ft/mi« (l,8mjsec) 5,500ft V 680 m) 4,200ft (/ 280 m) 13,500ft (4/20 m) 30 gai/hr </34,4 litresjhr) 477 miles (770 km) 6.800 Jb (3 089 kg) (I 192 kg) 4,395 1b (1893 kg) 41ft 8|in (/2,70 m) 5ft 11 in (1,80 m) 14ft Sin (4,46 m) 53ft (14,10 m) 8ft Sin (2,64 m) lift (3,35 m) The empty weight quoted a Dove relers to the utility cabin interior with ten troop- type seats, basic soundproofing and radio equipment. The executive layout wLh six seats involves a weight increase of approximately 175 ib Weights of other items of optional equipment are : cabin heater and defroster, 66 ib ; all-metal amphib- ious landing-gear, 385 Ib : power-operated hoist, 54 Ib ; F-4A attitude gyro, C-2 gyrosyn compass, and landing lights—: II for night and blind flying—46 Ib ; double- capacity (200 amp) generator, 10 Ib. Max rate of climb at sea level Vertical rate of climb at sea level ... .*• Hovering ceiling with ground effect Hovering ceiling without ground effect ... Service ceiling Fuel consumption (cruising) Range (with reserve) ... Gross weight ... . Useful load 2,405 1b Weight empty ... Fuselage length Fuselage width Height overall Main rotor diameter (blade tip circle) Tail rotor diameter (biade-tip circle) Main landing gear cread layouts to accommodate six passengers, luggage and freight (side elevation, and plan at top left); ten troops; or <pf stretchers in Hen of three—all in addition to'lm aircrew of two.
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