|Role||rescue or communications helicopter|
|Primary users||Royal Navy|
Royal Air Force
|Developed from||Sikorsky H-5|
Design and development
In December 1946 an agreement was signed between Westland Aircraft and Sikorsky to allow a British version of the S-51 to be manufactured under license in the United Kingdom. These would be powered by the 500 hp Alvis Leonides radial engine. A modified version was also developed by Westland as the Westland Widgeon, but it was commercially unsuccessful.
The Dragonfly entered service with the Royal Navy in 1950 in the air-sea rescue role. A number were also used by the Royal Air Force for casualty evacuation. It was replaced in British service by the Westland Whirlwind, another derivative of a Sikorsky design, in the late 1950s. Fifty-one civilian WS-51s were produced.
- Westland/Sikorsky WS-51
- Dragonfly HR.1
- Air-sea search and rescue helicopter for the Royal Navy powered by a 540 hp (400 kW) Alvis 50 radial piston engine. Thirteen built, some modified later as HR.5s.
- Dragonfly HC.2
- Casualty evacuation helicopter for the Royal Air Force similar to the commercial Mark 1A, three built.
- Dragonfly HR.3
- Air-sea search and rescue helicopter for the Royal Navy. Similar to the Dragonfly HR.1, but fitted with all-metal rotor blades, 58 built some later modified as HR.5s.
- Dragonfly HC.4
- Casualty evacuation helicopter for the RAF similar to the Dragonfly HR.3 with all-metal rotor blades, 12 built.
- Dragonfly HR.5
- Air-sea search and rescue helicopter for the Royal Navy similar to the Dragonfly HR.3. Modified from HR.1 and HR.3.
- Westland-Sikorsky WS-51 Mk.1A
- Civil transport helicopter powered by a 520 hp (388 kW) Alvis Leonides 521/1 radial piston engine. Built by Westland in the United Kingdom.
- Westland-Sikorsky WS-51 Mk.1B
- Civil transport helicopter powered by a 450 hp (336 kW) Pratt & Whitney R-985 Wasp Junior B4 radial piston engine.
- Sabena - Three helicopters
- Royal Egyptian Air Force - Two helicopters as VIP transports.
- French Air Force - Nine helicopters initially for use in Indo-China.
- Royal Iraqi Air Force - Two helicopters
- Italian Air Force - Three helicopters
- Royal Ceylon Air Force - Two helicopters
- Japan Air Self Defense Force - Three helicopters
- 153rd Rescue Squadron
- Tohuku Electrics - Two helicopters for power line inspection.
- Royal Thai Air Force - Four helicopters
- Empire Test Pilot's School
- Royal Air Force
- Central Flying School
- No. 194 Squadron RAF
- Fleet Air Arm
- SFR Yugoslav Air Force - Ten helicopters
- Dragonfly HR.3 WG751 on display at the Chatham Historic Dockyard, Chatham, United Kingdom.
- Dragonfly HR.5 WN403 on display at the Fleet Air Arm Museum at RNAS Yeovilton in Somerset, United Kingdom
- Dragonfly HR.3 G-AJOV on display at the Royal Air Force Museum Cosford, Shropshire, United Kingdom
- WS-51 Mk.1B 11503 on display at the Yugoslav Aeronautical Museum at Nikola Tesla Airport, Belgrade, Serbia.
- Dragonfly Mk.1A WS-51 H1-4/96, (cn WA/H/120) at Royal Thai Air Force Museum, Don Muang AFB.
- Dragonfly HR.5 WG724 on display at the North East Aircraft Museum, Sunderland, United Kingdom
- Dragonfly HR.5 on display at the Sri Lanka Air Force Museum, SLAF Ratmalana, Sri Lanka
- Dragonfly HR.5.Mk.5 On display at (The Helicopter Museum) Weston-super-Mare (North Somerset), (United Kingdom)
Specifications (Dragonfly HR.1)
Data from 
- Crew: 1 (pilot)
- Capacity: 3 (passengers)
- Length: 57 ft 6½ in (17.54 m)
- Main rotor diameter: × 48 ft 0 in (14.63 m)
- Height: 12 ft 11½ in (3.95 m)
- Main rotor area: 1809.56 ft2 (168.11 m2)
- Empty weight: 4380 lb (1987 kg)
- Gross weight: 5870 lb (2663 kg)
- Powerplant: 1 × Alvis Leonides 50 radial piston, 540 hp (403 kW)
- Maximum speed: 95 mph (153 km/h)
- Range: 300 miles (483 km)
- Service ceiling: 12,400 ft (3780 m)
- Sikorsky R-4
- Sikorsky H-5
- Westland Widgeon
- List of helicopter models
- List of aircraft of the Royal Air Force
- List of aircraft of the Fleet Air Arm
- Orbis 1985, page 3080
- The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). Orbis Publishing.
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