XT788 Wasp History Interact! Resources

The helicopter 'twins' produced by Westland as the Scout and Wasp originated in November 1957 when Saunders-Roe Ltd. began its design of a private venture for a Skeeter development and replacement. Two prototypes of the aircraft, then known as the Saro P.531, were begun early in 1958, the first (G-APNU) flying on 20 July and the second (G-APNV) on 30 September 1958. Several Skeeter components were used in their construction, including the tailboom, short-legged tricycle undercarriage and rotor blades (the P.531 having a 4-blade assembly). Both prototypes were powered by Blackburn-built Turmo 603 shaft turbines, derated to 325shp.
 
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Westland, after acquiring Saunders-Roe in 1959, took development an important stage further by completing two more prototypes with double the power and various other changes including a skid undercarriage. A Blackburn A129 (later known as the Nimbus) derated to 635shp powered G-APVL, which flew on 9 August 1959, while G-APVM, flown on 3 May 1960, was given a Gnome H.1000 engine derated to 685shp. The first firm order for this general purpose helicopter came from the Army Air Corps, a pre-series batch of P.531-2 Mk.1's basically similar to G-APVL being ordered in 1959. The first of these was flown on 4 August 1960, and in the following month a substantial Army order was placed for the type as the Scout AH Mk.1. Delivered from spring 1963, these are 5-seaters with Nimbus 101 or 102 engines and skid landing gear. They have replaced the Skeeter both at home and abroad and are employed for duties that include passenger or freight transport, liaison, search and rescue, and training. The Scout can also be used for casualty evacuation, carrying 2 stretchers inside the cabin and 2 more supported externally. Up to the spring of 1968 about one hundred and fifty Scouts had been built, these including deliveries to the Royal Australian Navy (two for shipborne survey work), Royal Jordanian Air Force (three), and the police departments of Bahrain (two) and Uganda (two).

Parallel development of the Wasp anti-submarine version has taken a little longer, due to exhaustive Naval trials carried out from November 1959 with a modified G-APNV and two specially-built P.531-0/N's, which also had Turmo engines but were fitted with a long-stroke quadricycle wheel undercarriage as well as landing skids. The Wasp is designed to operate from platforms on the rear decks of frigates, primarily as an extension of the ship's ability to attack submarines, but carrying no search gear. Production Wasps differ from the Scout in having the 710shp (derated) Nimbus 103 or 104 engine, long-stroke, fully-castoring wheel undercarriage (but no skids) and a half-tailplane at the top of the tail rotor pylon on the starboard side. (The Scout has a full tailplane below the tailboom.) The Wasp's main rotor blades and its entire tail section can be folded for stowage on ship. A weapon load of some 244kg can be attached to the underside between the undercarriage legs; this may comprise two Mk.44 homing torpedoes or an equivalent weight of depth charges or bombs. The Wasp HAS Mk.1 entered service in October 1963, and first production machines were allocated to No.829 Squadron and deployed singly aboard the Royal Navy's seven Tribal class and seven Leander class frigates. Other Wasps have been ordered by the navies of Brazil (three), the Netherlands (twelve), New Zealand (two) and South Africa (ten).

K.Munson "Helicopters And Other Rotorcraft Since 1907", 1968
Development of the Wasp/Scout family was initiated by Saro in 1957, with the aim of developing an aircraft based on the earlier Skeeter helicopter, but of more modern design, above all in terms of the powerplant. The result was the P.531 project, which aimed to use various components of the Skeeter; the first of two prototypes, both powered by a 400shp Turbomeca Turmo 603, flew on 20 July 1958. In 1959, Westland acquired Saro and decided to continue development of this interesting light helicopter. Another two prototypes were built, the first with a 1050shp Bristol Siddeley Nimbus engine derated to 635shp, and the other with a de Havilland Gnome H.1000 turbine derated to 685shp.

The British Army ordered a pre-production model and this was followed in September 1960 by an order for 66 of the P.531-2 Scout AH Mk.1 with 968shp Rolls-Royce Nimbus turbine engines (derated to 685shp). Another order was placed for 40 helicopters in September 1964.

The Scout was suited to all the tasks of a lightweight helicopter: observation, liaison, training, SAR. Several orders were also received from abroad: Royal Australian Navy (2), Royal Jordanian Air Force (3), Uganda (2) and Bahrain (2). The last two countries used them for police work. A total of 150 Scouts were built. Although its characteristics were not outstanding, the Scout fulfilled a role in the British Army which was played by the Bell 206 in many other armies, and has only recently been superseded by the Westland Lynx.

Development of the naval version of the Wasp proceeded more-or-less in parallel, but took longer. The Royal Navy used one of the prototypes, suitably modified with higher skids suitable for deck landings, and also ordered two P.531s powered by Nimbus turbine engines for deck landing and operational trials. The three aircraft performed exhaustive take-off and landing trials from the escort vessel HMS Undaunted in November 1959. The definitive Wasp was mainly intended for ASW from frigates of the Tribal and Leander classes and similar vessels; for this purpose it could carry one or two 122kg torpedoes or 250kg of depth charges. In September 1961, the type was ordered for the Royal Navy under the name Wasp HAS Mk.1 (the first flew on 28 October 1962 with a 968shp Nimbus engine derated to 710shp) and went into service in October 1963, performing 200 day and night landings on HMS Nubian.

The Wasp differed from the Scout mainly in the long-stroke landing gear with fully castoring wheels and the small tailplane on the starboard side of the tail rotor pylon. The main rotor and tail boom could be folded for stowage on board ship.

The Wasp, of which 63 were built, was primarily an antisubmarine helicopter in the "killer" role. It has been replaced by the Lynx in the Royal Navy but the following navies are still operating the Wasp: South Africa, Brazil, New Zealand, and Indonesia (which purchased ten second-hand aircraft from Holland when the latter's navy replaced its Wasp fleet with the Westland Lynx).

G.Apostolo "The Illustrated Encyclopedia of Helicopters", 1984