 The Royal Navy selected the Sea King to meet a requirement for an anti @-@ submarine warfare ( ASW ) helicopter to replace the Westland Wessex , placing an order with Westland for 60 SH @-@ 3D Sea Kings in June 1966 . The prototype and three pre @-@ production aircraft were built by Sikorsky at Stratford , Connecticut and shipped to the United Kingdom to act as trials and pattern aircraft . The first of the SH @-@ 3Ds was initially fitted with General Electric T58s and , after being shipped from the United States , was flown in October 1966 from the dockside at Avonmouth to Yeovil airfield . The other three were delivered from the docks , by road to Yeovil , for completion with British systems and Rolls @-@ Royce Gnome engines . The first Westland @-@ built helicopter , designated Sea King HAS1 , flew on 7 May 1969 at Yeovil . The first two helicopters were used for trials and evaluation by Westland and the Aeroplane and Armament Experimental Establishment ; subsequent production Sea Kings were delivered to the Royal Navy 's 700 Naval Air Squadron from August 1969 onwards . 
