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Airspeed AS.6 Envoy

as6envoy
AS.6 Envoy

 

The design of the AS.6 Envoy, began in late 1933 as and Hessell Tiltman, the technical director and chief designer based it on the Courier and using as many common parts as possible and their new Javelin or the Wolseley A.R.9 engine. T. Neville Stack was finally content with a Cheetah-engined machine with a cruise speed of 180 mph and endurance of six hours.


Tiltman followed the same basic construction as the Courier. The airframe was of wooden construction, the fuselage was a semi-monocoque structure in two sections, the front fuselage comprising the cockpit, cabin, toilet and luggage compartment and the rear fuselage carrying the tail unit. The doors and windows were built integrally with the sides and the stressed ply skin cut away before assembly. All the major fuselage sections were jig-built with longerons of spruce and a skin of birch ply laid at an angle of 45 degrees. No diagonal bracing was needed, as the skin carried all the shear loads, bending loads being carried by the longitudinal members.


The fuselage shell comprised two sides, a bottom and a top panel, to form a light, rigid box. The top and bottom curvature was formed with formers and stringers covered in fabric. With accommodation for a pilot and eight passengers the Envoy had all control surfaces fabric-covered, and a retractable tailwheel type landing gear and a variable-incidence tailplane were fitted.


Three versions were produced. The Series 1 and 2 Envoys had a twin-spar wing with Warren girder inter-spar bracing. The leading edge was covered by 1mm ply, and the wing was fabric covered. It was stiff in torsion and was complicated to build. The Series I (17 examples built) was without trailing-edge flaps; the Series II (13 built) introduced hydraulically operated split flaps which extended from the aileron to wing root on the trailing edge of each wing, and also from wing root to wing root beneath the centre-section. With flaps down the stalling speed was reduced by 11 mph (177 kph). The Series III (19 built) was similar, but had a number of detail improvements. The Series 3 Envoy, introduced at the end of 1936, was built with a ply-covered wing, the two spars forming a torsion box to eliminate the Warren girder bracing and give a stronger and stiffer wing. The production time for the wing was reduced by 35-40 percent. The tail unit was a wooden structure, fabric covered. The undercarriage, operated by a hydraulic handpump, was geometrically and functionally similar to the Couriers.


In parallel with the design work on the Envoy, Tiltman was also working on the Cheetah-engined machine for Stack. This required so many variations from the basic Envoy that it was decided to identify it as the A.S.8, to be known as Viceroy.


Soon after the 1934 SBAC Show at Hendon, Tiltman received from the Air Ministry an invitation to tender for an Envoy converted to a Coastal Patrol aircraft. Nothing more was heard of the project.


The prototype first flew on 26 June 1934 and 50 were built, including the prototype, by Airspeed for British, Japanese, Czechoslovakian, and Chinese. South Africa acquired seven Envoys in 1936: three of these were used by the SAAF and had an armament comprising a forward firing machine-gun and a dorsal gun turret. The four civil Envoys which made up the total, and which were for operation by South African Airways, were capable of quick conversion for use in a military role. A small number were supplied to the RAF. A number were used in the Spanish Civil War. Mitsubishi also built a number under licence.


Engines fitted to Envoys included the Wolseley AR.9, Scorpio I or Aries III, Armstrong Siddeley Lynx IVC or Cheetah IX, Wright Whirlwind R.760 and Walter Castor II.

 

AS.6
Engine: 2 x Wolseley AR.9, 149-kW (200-hp)

AS.6A
Engine: 2 x Armstrong Siddeley Lynx IVC, 179-kW (240-hp)

AS.6D
Engine: 2 x Wright R-760-E2 Whirlwind 7, 261 -kW (350-hp)

AS.6E
Engine: 2 x Walter Castor II, 254-kW (340-hp)

AS.6G
Engine: 2 x Wolseley Scorpio I, 186-kW (250-hp)

AS.6H
Engine: 2 x Wolseley Aries III, 168-kW (225-hp)

AS.6J
Engine: 2 x Armstrong Siddeley Cheetah IX, 261-kW (350-hp)
Maximum speed at 2225m (7,300ft): 338 km/h / 183 kts / 210 mph
Cruising speed at 3050m (10,000ft): 290 km/h / 157 kts / 180mph
Service ceiling 6860m (22,500ft)
Range: 1046 km / 565 nm / 650 miles
Empty weight: 1840kg (4,057 lb)
Maximum take-off weight: 2858 kg (6,300 lbs)
Wing span: 15.95m (52ft 4in)
Length: 10.52m (34ft 6in)
Height: 2.9m (9ft 6in)
Wing area: 31.49 sq.m (339sq.ft)
Wing load: 18.66 lb/sq.ft / 91.0 kg/sq.m

AS.6JM/C
Engine: 2 x Armstrong Siddeley Cheetah IX, 261-kW (350-hp)
Take-off weight: 2960 kg / 6526 lb
Empty weight: 1920 kg / 4233 lb
Wingspan: 15.9 m / 52 ft 2 in
Length: 10.5 m / 34 ft 5 in
Height: 2.8 m / 9 ft 2 in
Wing area: 31.5 sq.m / 339.06 sq ft
Max. speed: 325 km/h / 202 mph
Cruise speed: 270 km/h / 168 mph
Ceiling: 6700 m / 22000 ft
Range: 990 km / 615 miles
Crew: 2
Passengers: 6

 

airspeed_envoy




 


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