The Whirlwind HAS.7 was a naval helicopter built under licence by Westland Aircraft. It first took flight in 1953 and was officially introduced in 1954.
The Whirlwind is actually a modified version of the Sikorsky S-55, also known as the H-19 Chickasaw in its military guise.
Prior to the Whirlwind, Westland had already built a version of the S-51, another Sikorsky stalwart. That model was designated the Dragonfly. It was therefore natural that, when looking for a larger helicopter, Westland purchased the rights to the S-55.
The helicopter was mainly used by the Royal Navy to perform anti-submarine and search and rescue missions.
Powered by two 750 horsepower radial engines from Alvis Leonides Major, the Whirlwind had a substantial amount of lift for the time period. It could hover at up to 9 400 feet and range as far as 334 miles at 86 miles per hour.
The Alvis engines were only added later however, with early performance limited by underpowered Wasp or Cyclone engines. Later models were converted from radial to turboshaft engines. Specifically the Rolls-Royce Gnome. That variant was given the designation HAR.9.
The HAS.7 Whirlwind has the distinction of being the first helicopter specifically designed for frontline anti-submarine warfare. However, a single Whirlwind could not carry both a sonar and a torpedo, so some performed as “hunters” and others as “killers”.
Killer HAS.7 units could carry either a Mark 30 or a Mark 44 torpedo.
Almost all Whirlwinds served the Royal Navy’s Fleet Air Arm and in total about 400 were built. Of that number 100 units were exported to other nations. The French Navy, for example, received 37 HAR.2 variants between 1954 and 1957.