The Vickers Viscount was a British medium-range turboprop airliner first flown in 1948 by Vickers-Armstrongs, the first such aircraft to enter service in the world. A product of the Brabazon Committee, it used a new form of propulsion, the turboprop engine, replacing the conventional piston engine.
The Viscount was well received by the public for its cabin conditions, which included pressurisation, reductions in vibration and noise, and panoramic windows. It became one of the most successful and profitable of the first post-war transport aircraft; 445 Viscounts were built for a range of international customers, including in North America.
The Viscount was a response to the Brabazon Committee's Type II design for a post-war small medium-range pressurised aircraft to fly less-travelled routes, carrying 24 passengers up to 1,750 mi (2,816 km) at 200 mph (320 km/h). During discussions between the committee and Vickers' chief designer, Rex Pierson, Vickers advocated turboprop power. The committee was not convinced and split the specification into two types, the Type IIA using piston power, which led to the Airspeed Ambassador, and the turboprop-powered Type IIB which Vickers was selected to develop in April 1945. British European Airways (BEA) was involved in the design and asked that the aircraft carry 32 passengers instead, but remained otherwise similar.
The first design in June 1945 was based on the Viking with four turboprop engines and 24 seats and designated the VC-2 or Type 453. Later a double-bubble fuselage was proposed to give extra underfloor cargo space. Neither was pressurised but it was soon realised that for economical operation an altitude above 20,000 ft (6,100 m) was needed. Thus pressurization was required. The decision for pressurization resulted in the double-bubble and elliptical fuselage designs being abandoned. A circular cross-section variant was offered at the beginning of 1946. The resulting 28-seat VC-2 was financed by the Ministry of Supply with an order for two prototypes. But, before the contract was signed, the government asked for the capacity to be increased to 32. This stretched the fuselage increase from 65 ft 5 in (19.94 m) to 74 ft 6 in (22.71 m) and meant an increased wingspan of 89 ft (27 m).[N 1]
The contract for the aircraft to Air Ministry specification C.16/46 was signed on 9 March 1946 and Vickers allocated the designation Type 609 and the name Viceroy. Although George Edwards had always favoured the 800 hp Rolls-Royce Dart other engines were considered, including the Armstrong Siddeley Mamba which the government specified for the two prototypes, the choice of the Mamba engine increased the weight but Vickers made sure the engine nacelle would fit either the Mamba or Dart. While the Dart progressed better in development, the government asked in August 1947 for the second prototype to be Dart-powered. The second prototype was designated the 630 and was named as the Viscount. The first prototype already under construction was converted to the Dart as a 630 as well.
The resulting Vickers Type 630 design was completed at Brooklands by chief designer Rex Pierson and his staff in 1945, a 32-seat airliner powered by four Dart engines for a cruising speed of 275 mph (443 km/h). An order for two prototypes was placed in March 1946, and construction started in the company's Foxwarren Experimental Department. Originally Viceroyafter the viceroy of India, Lord Louis Mountbatten, the aircraft was renamed Viscount following India's independence in 1947. There was work on replacing the Darts with the Mamba, but this was dropped by the time the prototypes were reaching completion. After Pierson's death in 1948, George Edwards (later Sir George Edwards) took over as chief designer and assumed all technical control over the Viscount project.
"Never having flown other than piston-engined aircraft I was tremendously impressed with the smoothness of the four Dart turboprop engines. As I sat in the cabin, a coin was balanced on its edge on the table..."
The prototype Type 630, registered G-AHRF, made its maiden flight from the grass airfield at Wisley on 16 July 1948, piloted by Joseph "Mutt" Summers, Vickers' chief test pilot. The design was considered too small and slow at 275 mph (443 km/h), making the per passenger operating costs too high for regular service, and BEA had placed an order for 20 piston-engined Airspeed Ambassadors in 1947. Retrospectively commenting on Britain's aviation industry, Duncan Burn stated: "Had BEA committed itself to full support of the Viscount... it was quite likely that the smaller version would have gone into production... It was in a sense BEA's lack of enthusiasm for the [Type] 630 which made possible the [Viscount's] success."
Early flight trials, however, showed the qualities of a turboprop, resulting in a February 1949 order from the Ministry of Supply for a prototype of a stretched version with more powerful engines, the Type 700. Meanwhile, the first prototype Type 630 was awarded a restricted Certificate of Airworthiness on 15 September 1949, followed by a full certificate on 27 July 1950, which allowed the aircraft to be placed into service with BEA on 29 July to familiarise the pilots and ground crew with the new aircraft. It flew scheduled flights between London and Paris, and London and Edinburgh for a month. The 29 July flight between Northolt and Paris – Le Bourget Airport with 14 paying passengers was the first scheduled airline flight by any turbine-powered aircraft.
Type 663 Tay Viscount demonstrating at Farnborough in September 1950
The second prototype Viscount, the Type 663 testbed, had two Rolls-Royce Tay turbojet engines and first flew in RAF markings as serial VX217 at Wisley on 15 March 1950. It was demonstrated at the Farnborough SBAC Show in September and was later used in the development of powered controls for the Valiant bomber. It later saw use as a test bed by Boulton Paul Ltd for the development of electronic flight controlsystems.
The designers then went back to the drawing board and the aircraft emerged as the larger Type 700 with up to 48 passengers (53 in some configurations), and a cruising speed of 308 mph (496 km/h). The new prototype G-AMAV first flew from Brooklands on 28 August 1950, and served as a development aircraft for the type for several years. In late August 1950, BEA placed an order for 20 aircraft; further orders would come in the following year from operators such as Air France, Aer Lingus and Misrair. In 1953, the basic cost given for a Viscount was £235,000.
Performance and changes
One commentator, after travelling on an Air France Viscount, wrote in 1953: "Noise level was less than that of piston engines. It was a definite relief to be rid of the rough vibrations... The turboprop is an excellent shorthaul airplane and a definite crowd pleaser. The substitution of a lower constant pitch noise and smoothness for the vibration, grunts, and groans of the piston engine gives the hesitant passenger a feeling of confidence." The Viscount's cabin windows were ellipses measuring 19 by 26 inches.[N 2] The Viscount had lower operational costs than many rival aircraft; Vickers projected a 700 could carry a 13,000-lb payload from Chicago to New York in 2 hours 45 minutes against a 10-mph headwind, burning 6395 lb of fuel.
"In the field of intercity transports employing the propeller turbine, the Vickers Viscount Model 700 appears to be considerably superior to anything else in its class. [It has] exceptionally fine flying qualities and is a most comfortable vehicle in which to travel."
All production Viscounts were powered by the Rolls-Royce Dart turboprop engine; From its initial 800 hp, and then 1,000 hp and higher, Rolls-Royce extensively developed the Dart engine, due to its popularity and use on the Viscount and several later aircraft.[N 3] One key model was the Dart 506 engine, which had far greater fuel efficiency than earlier models, this enabled the airlines to deploy their Viscounts onto longer routes and to carry a greater maximum weight. Coupled with the availability of increasingly powerful engines Vickers continued to develop and modify the Viscount's design;[N 4] later models could carry increasing numbers of passengers and had fewer load limitations.
There were three basic versions of the Viscount. The first production version was the type 700 powered by R.Da.3 Dart 505 and later R.Da.3 Dart 506s. A sub variant were the type 700Ds powered by R.D.a Dart 510s.
The second version was the type 800. The 800s were shorter ranged, higher passenger capacity aircraft than the 700s. The fuselage was lengthened 3' 10" and the rear pressure bulkhead was moved aft 5' 5" allowing more passengers to be carried. The 800s (excepting the 806s) were powered by the Dart 510.
The third and final type of Viscount were the 810s. The same size as the 800s but powered with R.Da. 7/1 Mk 225 or Mk 530 Darts. With the greater power the 810s were faster and longer ranged than the 800s.
Proposed type 740, 850 and 870 Viscounts never made it beyond the drawing board.
The Viscount's good performance and popularity with customers encouraged Vickers to privately finance and develop an enlarged and re-engined variant of the Viscount, later designated as the Vickers Vanguard. The Vanguard drew extensively from the knowledge and design of the Viscount, and likewise maintained its advantage of lower operating costs over pure jet-powered aircraft, but its disadvantage in being slower than jet aircraft became increasingly critical as jets became more available over time.