|A Royal Air Force Whirlwind HAR.10 of the RAF Search and Rescue Force|
|National origin||United Kingdom|
|First flight||August 1953|
|Primary users||Royal Navy|
Royal Air Force
|Developed from||Sikorsky H-19|
The Westland Whirlwind helicopter was a British licence-built version of the U.S. Sikorsky S-55/H-19 Chickasaw. It primarily served with the Royal Navy's Fleet Air Arm in anti-submarine and search and rescue roles.
In 1950, Westland Aircraft, already building the American Sikorsky S-51 under licence as the Westland Dragonfly, purchased the rights to manufacture and sell Sikorsky's larger Sikorsky S-55 helicopter. While a Sikorsky-built pattern aircraft was flown by Westland in June 1951, converting the design to meet British standards (including the provision of a revised main-rotor gearbox), was time-consuming, and the first prototype British aircraft, registered G-AMJT, powered by the 600 hp Pratt & Whitney R-1340-40 Wasp did not fly until August 1953. This was followed by ten Whirlwind HAR.1s, which entered service shortly afterwards. They served in non-combat roles, including search and rescue and communications functions. The HAR.3 had a larger 700 hp Wright R-1300-3 Cyclone 7 engine.
The performance of early versions was limited by the power of the American Wasp or Cyclone engines, and in 1955, the HAR.5, powered by an uprated engine, the Alvis Leonides Major, flew for the first time. This was followed by the similarly powered HAS.7, which became the first British helicopter designed for anti-submarine warfare in the front-line when it entered service in 1957. It could either be equipped with a dipping Sonar for submarine detection or carry a torpedo, but could not carry both simultaneously, so sonar equipped "Hunters" were used to direct torpedo armed "Killers". The HAS.7 was powered by a 750 hp (560 kW) Alvis Leonides Major 755/1 radial engine. It had a hovering ceiling at 9,400 ft (2,900 m) and a range of 334 miles at 86 mph.
In 1960 Westland introduced a Whirlwind powered by the 1,000 hp Bristol Siddeley Gnome turboshaft, the greater power giving much improved performance over the earlier piston-engined variants; helicopters receiving this modification were redesignated as the HAR.9. The Gnome featured an early computer controlled fuel system that removed variations in engine power and made for much easier handling by the pilot.
More than 400 Whirlwinds were built, of which nearly 100 were exported to foreign customers.
848 Naval Air Squadron of the Royal Navy's Fleet Air Arm was the first squadron to receive HAR.1s, which replaced Sikorsky-built HAR.21 versions of the Whirlwind, for utility and search-and-rescue service from July 1954. After entering service with the Royal Navy, the Whirlwind also entered service with the Royal Air Force and French Navy, which received 37 Whirlwind HAR.2 between 1954 and 1957.
The Royal Air Force Search and Rescue Force used Whirlwinds painted in overall yellow for rescuing people in distress around the coast of the United Kingdom. Westland Wessex, and eventually Westland Sea King, helicopters later supplemented and eventually replaced Whirlwinds in this role.
The model numbers for the US-built evaluation models were
Main article: List of Westland Whirlwind operators
Yugoslavia 19 helicopters 
Data from Westland Aircraft since 1915 
The character of Harold the Helicopter, from the British television show Thomas & Friends, was based on a Westland Whirlwind with fitted pontoons.
It wasn't until 1955 that the Squadron reformed again, this time as a search and rescue unit equipped with Whirlwinds. It is in this guise that No. 22 Squadron exists today, having flown Wessex helicopters for a number of years before receiving Sea Kings in the mid-1990s.