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Airspeed Envoy

The Airspeed AS.6 Envoy was a twin-engined light transport aircraft designed and produced by the British aircraft manufacturer Airspeed Ltd.

Development
During the early 1930s, Airspeed successfully introduced the innovative Courier, the first British aircraft to feature a retractable undercarriage. On 26 June 1934, the prototype, G-ACMT, performed its maiden flight, piloted by C. H. A. Colman. Wolseley abruptly decided to cease aircraft engine manufacture in September 1936 as a result of the bureaucratic requirements of the Air Ministry being considered excessive by Lord Nuffield. Accordingly, Airspeed decided to adapt the aircraft to work with a variety of different engines. Early on, Airspeed promoted the Envoy by entering individual aircraft in air races and performing numerous long-distance flights. Production of the Envoy was produced in three distinct series; initial production aircraft lacked several of the features present on later-built examples, such as trailing edge flaps. Seventeen Series I Envoys were completed, followed by thirteen Series II aircraft (equipped with split flaps) and the improved Series III, of which nineteen were constructed. Akin to the preceding Courier, a 'colonial' model of the Envoy was developed for overseas customers. ==Design==
Design
The Airspeed Envoy was a twin-engined low-wing cabin monoplane of all-wood construction apart from fabric covered control surfaces. It had a rearward retracting main undercarriage with a fixed tailwheel. Having been designed from the onset as a twin-engined development of the company's earlier Courier, numerous commonalities were shared between the two aircraft, including near-identical wooden construction, the same outer wing panels and the main undercarriage. The airframe had a plywood exterior while the structure was composed of wood as well and was considered to be conventional for the era. In a typical configuration, the cabin could accommodate eight passengers along with a single pilot, while the Envoy's normal fuel capacity was 78 gallons, accommodated within a pair of aluminium tanks in the centre section. A separate aft compartment was normally used to store baggage, accessible via an exterior door on the starboard side of the aircraft. If the optional lavatory was installed, a reduced maximum capacity of six passengers was necessary. Passenger access to the cabin was via a single door on the port side of the aircraft. The wing of Envoy changed between models, with early-built aircraft not featuring flaps unlike later production models. It also featured outboard extension wings, which could optionally accommodate a pair of additional 30 gallon fuel tanks to extend the aircraft's range. The wing's center section was integral with the aircraft's semi-monocoque fuselage, possessing an aspect ratio of 8.16, a mean dihedral of 5 degrees, and an incidence of 2 degrees at the fuselage. The Envoy was powered by a range of engines across its various models. While initial aircraft were furnished with a pair of Wolseley Aries engines, other models were equipped with powerplants such as the Armstrong Siddeley Cheetah V and Armstrong Siddeley Lynx IVC radial engines. Regardless of the engine used, each was accommodated within an appropriate cowling, typically a short chord Townend ring, but also wider chord cowlings with and without blisters for cylinder heads. ==Operational history==
Operational history
Civilian use The first production Envoy I, G-ACVH, flew in October 1934 and was used as a company demonstrator. The second, also a Series I but fitted with Wolseley Aries III radial engines, A single Envoy participated in the Schlesinger Race to Johannesburg, but crashed midway through, killing two of its crew. Numerous early airlines adopted the Envoy for their fleets. The British company North Eastern Airways was the first to use the type as an airliner; multiple Envoys were used by the firm, which encountered difficulties on some routes due to limited passenger demand and navigation difficulties, leading to its discontinuation in 1938. The Indian operator Tata Air Service operated a single Envoy on a demonstration flight between Bombay (known as Mumbai today) and Calcutta (since re-spelt as Kolkata) on 25 February 1935 to validate the viability of air mail service between the two cities. Amongst the more successful airlines to operate the Envoy was Japan Air Transport Co. (NKYKK – Nihon Koku Yuso KK) and the Czechoslovak firm Czech Airlines (CSA), the latter having ordered four Envoys to launch its operations with on 1 October 1935. Orders for the Envoy came from a wide variety of customers, many of which were distributed across the British Empire. A pair of aircraft were delivered to the Ansett Airlines in Australia. The Spanish company Commercial Air Hire acquired one of the early-build Envoys for civilian purposes; it was subsequently impressed into military service along with several Envoys during the Spanish Civil War. During May 1937, the King's Flight took delivery of a single Envoy III as a replacement for a de Havilland Dragon Rapide; this aircraft received the registration G-AEXX and was painted in distinctive red and blue colours. Through the mid to late 1930s, several overseas companies entered negotiations with Airspeed with the aim of acquiring a licence to produce the Envoy themselves. The Japanese company Mitsubishi successfully did so, producing it as the Mitsubishi Hinazuru-type Passenger Transport. The Austrian firm Hirtenberger also secured a licence to locally manufacture the aircraft, while other entities, such as a Yugoslavian venture, also made efforts to secure similar accommodations. Military use The Envoy also saw military use, being adopted by the air arms of different countries. The aircraft was used in quantity by the Air Forces of Spain, Japan, South Africa, Finland, China, and the United Kingdom, along with several additional nations. Seven Envoys were ordered for joint use by the South African Air Force (SAAF) and South African Airways, with three being delivered in military form and four delivered to South African Airways, where they were used on the air route between JohannesburgBloemfonteinPort Elizabeth on 12 October 1936. These aircraft, known as the "Convertible Envoy", could be equipped at short notice with bomb racks and a machinegun in a hand-operated Armstrong Whitworth dorsal turret. Accordingly, each of these seven aircraft could be transformed by a work crew of four within four hours from the transport version into a light bomber or reconnaissance aircraft; in this configuration, the crew consisted of four; pilot, navigator, radio operator and gunner. While not a large order, Airspeed benefitted substantially from its work to develop the Convertible Envoy when it subsequently developed further militarised versions of the aircraft. During October 1936, the British Air Ministry placed a sizable order for 136 Envoys, specially equipped for crew training, to fulfil Specification T.23/36. These further developed aircraft were given a new company designation as the AS.10, and entered RAF service as the Airspeed Oxford. During the Spanish Civil War, ten AS.6 Envoys were obtained by the Spanish Republicans, with the Nationalist side using two, including one that defected from the Republicans, as transport, reconnaissance aircraft or light bombers. One of the Nationalist Envoys flew into a mountain in June 1937, killing General Emilio Mola; this Envoy had been their demonstrator and was sold for £6,000 cash (six £1000 Bank of England notes). During the Second World War, the German Luftwaffe captured several Envoys and operated a few as trainer aircraft for a time. Three months later, a follow-up order was placed four additional Envoys. Following the acquisition of a licence, local production of the aircraft started at the Nagoya Mitsubishi factory of the Mitsubishi Hinazuru-type Passenger Transport. It was initially powered by Gasuden Jimpu engines, but later using licence built Armstrong Siddeley Lynx or Wolseley Aries Mk.III engines. While largely identical to their British-made equivalents, Mitsubishi-built aircraft differed in that they were outfitted with landing flaps, along with additional supporting frames around the passenger cabin windows and a covering for the transport cockpit canopy. Flight testing of the Jimpu powered aircraft resulted in a crash, killing the flight test observer, (the first fatality during flight testing of Mitsubishi aircraft), blamed on the engines producing excessive drag, resulting in the switch to licence-built British engines. Eleven aircraft were built at Nagoya before production ceased, all of which flew domestic services for NKYKK (later to become Greater Japan Airways). Postwar era By the end of the Second World War, there were very few Envoys left in operation. One of the RAF Envoy IIIs that survived the conflict was subsequently disposed of as surplus and operated by Private Charter Ltd as G-AHAC for civil passenger charter flights, it was retired and finally scrapped at Tollerton airport, Nottingham during 1950. ==Variants==
Variants
;AS.6 Envoy I : Powered by two 200-hp (149-kW) Wolseley A.R.9 piston engines. 5 built ;AS.6A Envoy I : Powered by two 240-hp (179-kW) Armstrong Siddeley Lynx IVC radial piston engines. 5 built ;AS.6D Envoy II : Powered by two 350-hp (261-kW) Wright R-760-E2 Whirlwind 7 radial piston engines, eight built. ;AS.6E Envoy III : Powered by two 340-hp (254-kW) Walter Castor engines. 5 built ;AS.6G : Powered by two 250-hp (186-kW) Wolseley Scorpio I engines. ;AS.6H Envoy : Powered by two 225-hp (168-kW) Wolseley Aries III engines. 1 built ;AS.6J Envoy III: Seven-seat light transport aircraft. Powered by two 345-hp (257-kW) Armstrong Siddeley Cheetah IX radial piston engines. 27 built ;AS.6JC Envoy : Powered by two 350-hp (261-kW) Armstrong Siddeley Cheetah IX radial piston engines. 4 built ;AS.6JM Envoy : Powered by two 350-hp (261-kW) Armstrong Siddeley Cheetah IX radial piston engines. 3 built ;AS.6K Envoy III :Three-built. ;AS.8 Viceroy :A special, one-off racer developed for the MacRobertson Race from the Envoy. ;Airspeed LXM :One Envoy evaluated by the Imperial Japanese Navy Air Service ;Mitsubishi Hinazuru-type Passenger Transport :(Hinazuruen Young Crane) Licence production by Mitsubishi, fitted with flaps and powered by Gasuden Jimpu, or licence-built Armstrong Siddeley Lynx or Wolseley Aries Mk.III engines. Eleven built from 1936 to 1938 ==Operators==
Operators
The Envoy also saw service in China, the Independent State of Croatia, Finland, Slovakia, and Spain. ; • Ansett Airlines ; • Air Force of the Independent State of Croatia ; • ČSA ; • Finnish Air Force ; • Luftwaffe (small numbers) ; • Japan Air TransportImperial Japan Airways ; • Manchukuo National Airways ; • South African Airways operated four aircraft. • South African Air Force ; • Spanish Republican Air Force from LAPE ; • Spanish Air Force ; • North Eastern Airways • Olley Air Service • Portsmouth, Southsea and Isle of Wight Aviation • Private Charter Ltd • Royal Air ForceNo. 24 Squadron RAF. • No. 17 Group Communication Flight RAFFleet Air Arm ==Accidents and incidents==
Accidents and incidents
Cheetah-powered Envoy, VH-UXY, piloted by Charles Ulm, disappeared in December 1934 during an attempt to fly the Pacific route between Oakland and Honolulu. The Envoy prototype (demonstrator) was sold to the Spanish Nationalists for £6000 cash (six £1000 Bank of England notes) in September 1936 and used as a VIP transport. On 3 June 1937 it flew into a mountain killing all on board including General Mola. ==Specifications (AS.6J Series III )==
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