Like the United States Air Force (USAF) during the 1960s, the British Royal Air Force (RAF) also sought a tactically-minded Short Take-Off and Landing (STOL) aircraft of strong performance to replace a mixed and aging fleet of transports made up of Blackburn Beverly and Handley Page Hasting aircraft. Between two submissions, one from Hawker Siddeley and the other from Armstrong Whitworth (AW), the AW design was selected for development as the "AW.681" to fulfill "Operational Requirement 351". The project formally began in 1962 (under the designation of Hawker Siddeley "HS.681") with the goal of seeing a first-flight recorded sometime in 1966.
AW engineers selected a conventional arrangement for their new aircraft, incorporating swept-back wing mainplanes and a "T-style" tail unit. The empennage would be raised to accommodate a loading ramp under the tail and the flightdeck would be sat over the nose in the usual way. Two engine nacelles (with a deflected-thrust capability) would be held under each wing. The engine of choice became the Rolls-Royce RB.142 "Medway" of 13,790lb thrust each with the alternative being the Bristol Siddeley "Pegasus" ducted-flow turbofan (18,000lb thrust each) coupled with 18 x RB.162-64 "lifting fans" (6,000lb thrust output) installed to cover a Vertical Take-Off and Landing (VTOL) capability. A tricycle undercarriage would allow for ground-running. Blown flaps would aid in low-altitude control and short-field take-off and landing actions. Internally, the aircraft could carry around 35,000lb of cargo or sixty combat-ready troops.
Dimensions included a length of 104.1 feet, a wingspan of 134 feet and a height of 37.9 feet. Maximum Take-Off Weight (MTOW) would reach 181,200lb. Maximum speed was estimated at 545 miles per hour with a range out to 4,800 miles and a service ceiling of 25,000 feet.
Just as soon as the AW.681 project was to get "off the ground", it was cancelled by the incoming government (Labour Party) in February of 1965 after review of ongoing military programs. The RAF then decided to secure a fleet of Lockheed C-130 "Hercules" aircraft for the transport role instead and this marked the official end of the AW.681 tale. The aircraft existed for a short time beyond that when Armstrong-Whitworth attempted to sell the same aircraft (sans the complicated VTOL capability) by combining the existing designs of the AW.681 fuselage and tail with the wings and engines of the Hawker Siddeley "Nimrod". This idea did not progress.
The AW.681 product was also known as the Whitworth Gloster Model 681.
(OPERATORS list includes past, present, and future operators when applicable)
General transport functionality to move supplies/cargo or personnel (including wounded and VIP) over range.
✓X-Plane (Developmental, Prototype, Technology Demonstrator)
Aircraft developed for the role of prototyping, technology demonstration, or research / data collection.
104.2 ft (31.75 m)
134.0 ft (40.85 m)
37.9 ft (11.55 m)
181,573 lb (82,360 kg)
(Showcased structural values pertain to the base Armstrong Whitworth AW.681 production variant)
4 x Rolls-Royce Medway turbofan engines (with thrust deflection) developing 13,800lb of thrust each.
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