In December 1946, Westland Aircraft signed an agreement to build under licence the world’s first successful operational helicopter, the American Sikorsky S-51, which became the first production helicopter in Britain. Named the Dragonfly, the first British-built S-51 flew on 5 October 1948. Westland produced a total of 149. Of these 71 went to the Royal Navy, where they served mainly as plane guards to aircraft carriers to recover downed airmen, doing what had been the task for a destroyer and 250 men. A further 16 went to the Royal Air Force to form the first frontline helicopter squadron in the service.
WH991 first flew on 4 February 1953. Shortly afterwards it joined HMS Illustrious, but was soon returned to Westland for repairs. During the next few years it served on HMS Centaur and at Lee-on-Solent and Eglington in Northern Ireland. After modifications in 1958, WH991 was sent to Trinidad to serve on the survey ship, HMS Vidal. Back in England in 1960, the helicopter joined 700 Squadron at Yeovilton and 705 Squadron at Culdrose. In 1994, it was found in a nearby scrapyard by Museum member Ray McElwain, who has restored it for static display.