The Armstrong Whitworth Argosy was a British post-war transport/cargo aircraft; it was the final aircraft to be designed and produced by aviation company Armstrong Whitworth Aircraft. Although given different internal design numbers, the AW.650 civil and AW.660 military models were, for most practical purposes, the same design, while both models also shared the "Argosy" name. Development of the Argosy originates in the AW.66, a proposed twin-engined military transport that was designed with British Air Ministry's Operational Requirement 323 (OR323) in mind. While Armstrong Whitworth terminated work on the AW.66, it decided to go forward with a civilian-oriented derivative of the design, designated AW.65, as it was judged to be commercially viable. The AW.65 was redesigned to use four Rolls-Royce Dart turboprop engines, and thus was re-designated as the AW.650. On 8 January 1959, the first Argosy conducted the type's maiden flight. In December 1960, the type received Federal Aviation Administration (FAA) type certification, enabling the initial civil version, referred to as the Series 100, to enter civil service across most parts of the world. In Britain, military planners took interest in the Argosy and released a new specification for a militarised variant, designated AW.660. First flown on 4 March 1961, this model featured double the range of the Series 100 and otherwise differed by an alternative door arrangement, which was largely to facilitate paratroop operations. Furthermore, an improved civil variant, the Series 200, was introduced at the behest of airline British European Airways (BEA). First flown on 11 March 1964, this model featured a new wing incorporating a fail safe structure, being stronger and lighter than its original counterpart. The Argosy was operated by both the Royal Air Force (RAF) and various civil operators across the globe for numerous years. The type was withdrawn from RAF service during 1978, while the last Argosy was retired from civil operations during 1991. Development Background The development of the Argosy can be traced back to the development of Operational Requirement 323 (OR323) by the British Air Ministry. During 1955, a specification was issued based upon OR323, which sought a medium-range freight aircraft that would be capable of lifting a maximum payload of 25,000 lb (11,340 kg), while also possessing a range of when carrying up to . British aviation manufacturer Armstrong Whitworth Aircraft took interest in this specification and decided to allocate members of its design team to the task of developing a