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66-793: Originally, the aircraft was an upgraded version of the Pressurized Navajo equipped with two Pratt & Whitney Canada PT6 A-28 turboprop engines. Later, the aircraft was further refined and developed, including aerodynamic improvements and fuselage extensions. The PA-31T led to the development of the PA-42 Cheyenne III and IV . Data from Jane's All the World's Aircraft 1976–77 General characteristics Performance Related development Aircraft of comparable role, configuration, and era Pratt %26 Whitney Canada PT6 The Pratt & Whitney Canada PT6

132-410: A free power turbine . The starter has to accelerate only the gas generator, making the engine easy to start, particularly in cold weather. Air enters the gas-generator through an inlet screen into the low-pressure axial compressor . This has three stages on small and medium versions of the engine and four stages on large versions. The air then flows into a single-stage centrifugal compressor , through

198-608: 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. John Watkins, Chief Technical Officer of Trans Australia Airlines . All production Viscounts were powered by

264-529: A PT6 and propeller flying test-bed until it was replaced with a Beech King Air in 1980. The King Air test-engine or propeller replaced one of the standard ones. In 1974 the Beech 18 had been unable to fly fast enough and high enough to test the PT6A-50 for the de Havilland Canada Dash 7 so a Vickers Viscount was modified as a PT6 test-bed with a Dash-7 installation in the nose. The first production PT6 model,

330-433: A bleed arrangement which reuses the bleed air by returning it in a tangential direction at the entry to the compressor, an idea patented by Schaum et al. and titled "Turbine Engine With Induced Pre-Swirl at Compressor Inlet". It acts like a variable vane and is known as a "Jet-Flap". All versions of the engine consist of two sections that can be easily separated for maintenance: a gas generator supplies hot pressurized gas to

396-412: A development aircraft for the type for several years. In late August 1950, BEA placed an order for 20 aircraft; further orders came 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. One reporter, after travelling on an Air France Viscount, wrote in 1953: "Noise level was less than that of piston engines. It

462-588: A dozen Viscounts, and purchased later turboprop aircraft such as the Fokker F27 Friendship ; It later transitioned to jet aircraft as passenger demand outgrew the capacity of the Viscounts. To compete with its rival TAA, another Australian airline, Ansett-ANA also procured its own small Viscount fleet; the Viscount allowed Ansett to set out a faster and superior service than the larger TAA for

528-408: A folded annular combustion chamber , and finally through a single-stage turbine that powers the compressors at about 45,000 rpm. Hot gas from the gas generator flows into the power turbine, which turns at about 30,000 rpm. It has one stage on the small engines and two stages on the medium and large ones. For turboprop use, this powers a two-stage planetary output reduction gearbox, which turns

594-577: A possible new market such as a Super PC-12, a more powerful TBM, or a bigger King Air. When de Havilland Canada asked for a much larger engine for the DHC-8 , roughly twice the power of the Large PT6, Pratt & Whitney Canada responded with a new design initially known as the PT7, later renamed Pratt & Whitney Canada PW100 . The rate at which parts deteriorate in a gas turbine is unbalanced insofar as

660-581: A proposed 2,000 shp (1,500 kW) engine to replace the most powerful versions of the PT6. It was considered likely to be a development of the PT6C core, and would fit between the 1,750 shp (1,300 kW) PT6C-67C/E and the 2,300 shp (1,700 kW) PW100 family. It was expected to be ready to launch by the end of 2017 for an initial helicopter platform with a 10-15% reduction in brake specific fuel consumption . This 2,000 hp engine would target

726-725: A small gas turbine engine. Demand for the Wasp radial engine was still strong and its production was profitable but the aim was to become Canada's prime engine company by focusing on a small gas turbine engine. Riley gave Guthrie a modest budget of C$ 100,000. Guthrie recruited twelve engineers with experience gained at various places including the National Research Council in Ottawa , Orenda Engines in Ontario , Bristol Aero Engines and Blackburn Aircraft . They completed

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792-476: Is a turboprop aircraft engine produced by Pratt & Whitney Canada . Its design was started in 1958, it first ran in February 1960, first flew on 30 May 1961, entered service in 1964, and has been continuously updated since. The PT6 consists of two basic sections: a gas generator with accessory gearbox, and a free-power turbine with reduction gearbox. In aircraft, the engine is often mounted "backwards," with

858-531: Is an accepted version of this page The Vickers Viscount is a British medium-range turboprop airliner first flown in 1948 by Vickers-Armstrongs . A design requirement from the Brabazon Committee , it entered service in 1953 and was the first turboprop-powered airliner. 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

924-561: Is known for its reliability with an in-flight shutdown rate of 1 per 333,333 hours up to October 2003, 1 per 127,560 hours in 2005 in Canada, 1 per 333,000 hours from 1963 to 2016, 1 per 651,126 hours over 12 months in 2016. Time between overhauls is between 3,600 and 9,000 hours and hot-section inspections between 1,800 and 2,000 hours. Early PT6 versions lacked a FADEC , autothrottle could be installed as an aftermarket upgrade with an actuator , initially for single-engine aircraft like

990-478: Is known for its reliability, with an in-flight shutdown rate of 1 per 651,126 hours in 2016. The PT6A turboprop engine covers the power range between 580 and 1,940 shp (430 and 1,450 kW), while the PT6B/C are turboshaft variants for helicopters. In 1956, Pratt & Whitney Canada's (PWC) president, Ronald Riley, ordered engineering manager Dick Guthrie to hire a team of gas turbine specialists to design

1056-578: Is the same as in 1964, updates have included a cooled first-stage turbine vane, additional compressor and turbine stages and single-crystal turbine blades in the early 1990s. Its pressure ratio is 13:1 in the AgustaWestland AW609 tiltrotor, the highest that can be used without cooled turbine blades. In response to the General Electric GE93 , in 2017 Pratt & Whitney Canada started testing core technology and systems for

1122-642: 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

1188-504: The Cocos (Keeling) Islands to Melbourne's Essendon Airport in 10 hours 16 minutes (343.8 mph). Trans Australia Airlines (TAA) received its first Viscount in 1954, and the aircraft quickly proved profitable, leading to additional orders. The Viscount proved to be an invaluable aircraft for TAA, aviation author John Gunn stating, "TAA had achieved dominance on Australia's trunk routes with its turboprop Viscounts". TAA procured over

1254-625: The PC-12 and potentially in twin-turboprop aircraft. In October 2019 the PT6 E-Series was launched on the PC-12 NGX, the first general aviation turboprop with an electronic propeller and engine control system with a single lever and better monitoring for longer maintenance intervals, increased from 300 to 600 hours, and a TBO increased by 43% to 5,000 hours, reducing engine operating costs by at least 15%. In April 2022, Daher announced that

1320-407: The 700. The fuselage was lengthened 3 ft 10 in (1.17 m) and the rear pressure bulkhead was moved aft 5 ft 5 in (1.65 m), allowing more passengers to be carried. The 800s (excepting the 806s) were powered by the Dart 510. The third type of Viscount was the 810. It was the same size as the 800s, but was powered with R.Da. 7/1 Mk 225 or Mk 530 Darts. With the greater power,

1386-468: The 810 was faster and longer ranged than the 800. Proposed type 740, 850, and 870 Viscounts never left 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

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1452-461: The PT6 have appeared over time: The PT6A family is a series of free-turbine turboprop engines providing 500 to 1,940 shaft horsepower (370 to 1,450 kilowatts) BX Turbo de Havilland Canada Beaver DHC-2 (STC) ARON M80 (WIG CRAFT) Piper PA-46 (M700 Fury) The engine is used in over 100 different applications. Data from Jane's 62-63, Related development Comparable engines Related lists Vickers Viscount This

1518-467: The PT6, which first ran in December 1963, was beset with engineering problems, cost overruns and lack of sales. It was almost cancelled. The team lacked the ability to deal with the technical difficulties, i.e. how to develop the engine, because, as one of the team Elvie Smith recalled, they came from research and design backgrounds. They learned how to run a development program, such as testing around

1584-458: The PT6A-20, was the pipe diffuser patented by Vrana, another of the original PT6 team. It replaced the vaned type diffuser used in centrifugal compressors. The pipe diffuser became standard design practice for P&WC. Another design change improved the part-speed functioning of the compressor. It is common to bleed air from a compressor to make it work properly at low engine speeds. The PT6 has

1650-683: The PT6A-6, was certificated in December 1963. The first application was the Beech Queen Air , enticing the U.S. Army to buy a fleet of the U-21 Ute variant. This helped launch the King Air with Beechcraft selling about 7,000 by 2012. From 1963 to 2016 power-to-weight ratio was improved by 50%, brake specific fuel consumption by 20% and overall pressure ratio reached 14:1. Its development continues and while today its basic configuration

1716-523: The Rolls-Royce Dart turboprop; 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. One key model was the Dart 506 engine, with better fuel efficiency than earlier models, allowing airline Viscounts to fly longer routes, with more payload. With the availability of more powerful engines, Vickers continued to develop

1782-580: 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 trial 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 until 23 August 1950. The 29 July 1950 flight between Northolt and Paris – Le Bourget Airport with 14 paying passengers

1848-518: The US government imposed its embargo on Cuba in 1962, Cubana decided to sell all of its Viscounts. They were replaced by Soviet-built turboprop aircraft. South African Airways (SAA) was another major operator of the Viscount; by January 1959, it was operating on all of SAA's domestic routes. In 1961, SAA had seven Viscounts, and acquired a further aircraft from Cuba in the following year. In 1965, SAA began receiving Boeing 727s , which had been selected

1914-499: The Viscount 700 prototype G-AMAV achieved the fastest time (40 hours 41 minutes flying time) in the transport section of the 12,367 mi (19,903 km) air race from London to Christchurch , New Zealand. The aircraft averaged 320 mph (520 km/h) in the event, crossing the finish line nine hours ahead of its closest rival, a Douglas DC-6 A of KLM , with the latter winning on handicap. En route , equipped with extra fuel tanks, it flew 3,530 mi (5,680 km) nonstop from

1980-596: The Viscount became the mainstay of the route between Johannesburg in South Africa, Salisbury (now renamed Harare) in modern-day Zimbabwe , and London, England. CAA had enough Viscounts to entirely replace its Viking fleet and to occasionally lease them to other operators. More Viscounts were purchased by CAA right up until 1965, when CAA announced its intention to procure the British Aircraft Corporation 's jet-powered BAC 1-11 successor as

2046-734: The Viscount generated considerable interest from airlines and industry figures across the United States, including American aviation pioneer Howard Hughes , who purchased 15 Viscounts immediately after personally flying one. US Capital Airlines became an important operator of the Type 700 Viscount, using it heavily throughout the eastern US routes; in 1958, Capital reportedly had accumulated over 350,000 flight hours on its Viscounts, more than any other operator. Continental Airlines and Northeast Airlines also became US Viscount operators. The first airline in Latin America to operate

Piper PA-31T Cheyenne - Misplaced Pages Continue

2112-404: 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... Test Pilot Joseph Summers , commenting on flight characteristics of the Viscount. The prototype Type 630, registered G-AHRF , made its maiden flight from

2178-472: The Viscount was Cubana de Aviación . Cubana's −755D Viscounts, delivered in 1956, were placed on the Havana -Miami and Varadero -Miami routes, and were successful at raising Cubana's market share on these routes. During the 1958 Cuban elections, a Cubana Viscount was hijacked by gunmen aligned with the 26th of July Movement ; the aircraft crash-landed in the sea, reportedly killing 17 of the 20 occupants. When

2244-589: The Viscount with Britain directly. The last batch of six aircraft built was for the Chinese CAAC Airlines , which was delivered during 1964; at the end of production. 445 Viscounts had been manufactured. Many Viscounts were refurbished and saw new service with African operators; sales of these second-hand aircraft continued into the 1990s. The last airworthy Viscount, 9Q-COD, is believed to have been flown last in January 2009 for Global Airways in

2310-791: The Viscount with a newer turboprop aircraft, the Hawker Siddeley HS 748 . On 18 April 1996, British World Airlines conducted the last Viscount passenger service in Britain, exactly 46 years after BEA's inaugural flight; on board the flight were Sir George Edwards and Sir Peter Masefield . In late 1960, the People's Republic of China had begun negotiations with Vickers for as many as 40 Viscounts, but negotiations were protracted due to political tensions. At this point, China sought arrangements to purchase Viscounts second-hand from existing operators, and later achieved successive deals regarding

2376-428: The Viscount's design. Later models could carry more passengers and had fewer load limitations. Three basic versions of the Viscount were built. The first production version was the Type 700 powered by R.Da.3 Dart 505 and later R.Da.3 Dart 506s. A subvariant was the type 700Ds powered by R.D.a Dart 510s. The second version was the Type 800, which was shorter in range and had a higher passenger capacity aircraft than

2442-517: The Viscount, and maintained its advantage of lower operating costs over jet airliners, but its disadvantage in being slower became critical as jets became more available. Regular passenger flights were launched by BEA on 18 April 1953, the world's first scheduled turboprop airline service. BEA became a large user of the Viscount, as well the rival Handley Page Dart Herald ; by mid-1958, BEA's Viscount fleet had carried over 2.75 million passengers over 200,000 flight hours. Following BEA's launch of

2508-466: 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

2574-460: 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,

2640-586: 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 the designers soon realised that for economical operation, an altitude above 20,000 ft (6,100 m)

2706-460: The clock rather than on one shift, from a PWA team which directed the development for several months. The PT6 first flew on 30 May 1961, mounted as a third engine in the nose of a Beech 18 aircraft which had been converted by de Havilland at its Downsview facility in North York, Ontario . Full-scale production started in 1963, with service entry the following year. The Beech 18 continued as

Piper PA-31T Cheyenne - Misplaced Pages Continue

2772-584: 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

2838-525: The company's Foxwarren Experimental Department. Originally named Viceroy after the viceroy of India, Lord Louis Mountbatten , the aircraft was renamed Viscount following India's independence in 1947. Work took place 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

2904-714: The compressor intake by inertial separators in the inlet. In some installation such as the PT6A-66B version in the Piaggio P.180 Avanti , the engine is reversed, with the propeller acting as a "pusher", the accessory gearbox facing the front of the aircraft. By the 40th anniversary of its maiden flight in 2001, over 36,000 PT6As had been delivered, not including the other versions. Up to October 2003, 31,606 delivered engines have flown more than 252 million hours. Till November 2015, 51,000 have been produced. The family logged 400 million flight hours from 1963 to 2016. The PT6 family

2970-515: The detailed design of an engine for Canadair's small jet trainer, the CL-41 . It was a 3,000-pound-force (13 kN) thrust turbojet but the design was taken over by P&WA who developed it into the Pratt & Whitney JT12 . The team had to wait for market assessments to define their next engine, a 450 shaft horsepower (340 kW) turboprop for twin-engined aircraft, the PT6. The early development of

3036-477: The end of 1953, the order book had risen to 90, and 160 by the end of the following year. Vickers was able to quickly respond to the new orders, as it had gambled on such orders emerging and early on the decision had been taken to commit to a high production rate at the company's own risk. In 1957, the Vickers production line was producing the Viscount at a rate of one aircraft every three days. In October 1953,

3102-592: The first Viscount was delivered to Canada in a large media event that included an improvised aerial display. TCA became a prolific operator of the type, placing multiple follow-up orders for additional Viscounts. By 1958, TCA had an operational fleet of 51 Viscounts. Aviation author Peter Pigott later wrote: "For TCA and Vickers, the Viscount was a public-relations coup. Passengers loved the quiet ride and panoramic windows. No other airline in North America flew turbo-prop airliners then, and no other British aircraft

3168-492: The first time. The Two Airlines Policy was formally established in 1952 by the Fifth Menzies Ministry. The policy took practical effect when Ansett purchased the failing Australian National Airways in 1957, resulting in it being the only competitor for the government-owned TAA. Unstated was the requirement for both airlines to have identical equipment. The first North American airline to use turboprop aircraft

3234-445: The fuselage 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). 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

3300-464: 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

3366-421: The hottest parts need replacing or repairing more often than the cooler-running parts. If the hotter parts can be removed without disturbing the rest of the engine, for example without removing the complete engine from the aircraft, maintenance costs are reduced. It was achieved with the PT6 by having the hottest parts, the gas generator turbine and combustor, at the propeller end. They are removed without disturbing

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3432-427: The intake at the rear and the exhaust at the front, so that the turbine is directly connected to the propeller. Many variants of the PT6 have been produced, not only as turboprops but also as turboshaft engines for helicopters, land vehicles, hovercraft, and boats; as auxiliary power units; and for industrial uses. By November 2015, 51,000 had been produced, which had logged 400 million flight hours from 1963 to 2016. It

3498-465: The long-term successor to the Viscount. BEA, and its nationalised successor British Airways (BA), vigorously operated the Viscount on Britain's domestic routes. In the 1980s, BA began withdrawing its ageing Viscount fleet; all BA Viscount operations in Scotland had ended in 1982. Former BA aircraft were often sold on to charter operators such as British Air Ferries . Some airlines chose to replace

3564-465: The most successful and profitable of the first postwar transport aircraft; 445 Viscounts were built for a range of international customers, including in North America. The Viscount was a response to the 1943 Brabazon Committee's proposed Type II design for a postwar, 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

3630-464: The power section at the front of the nacelle, where it can drive the propeller directly without the need for a long shaft. Intake air is usually fed to the engine via an underside mounted duct, and the two exhaust outlets are directed rearward. This arrangement aids maintenance by allowing the entire power section to be removed along with the propeller, exposing the gas-generator section. To facilitate rough-field operations, foreign objects are diverted from

3696-416: The previous year as a jet-powered replacement for the Viscount. SAA sold its last Viscount to British Midland in the 1970s. Central African Airways (CAA) had been a traditional customer of Vickers, already operating a number of Vickers Vikings when it received its first Viscount on 25 April 1956. The introduction of the Viscount roughly coincided with the opening of a major airport at Salisbury , and

3762-428: The propeller at a speed of 1,900 to 2,200 rpm. The exhaust gas then escapes through two side-mounted ducts in the power turbine housing. The turbines are concentric with the combustion chamber, reducing overall length. In most aircraft installations the PT6 is mounted so that the intake end of the engine is towards the rear of the aircraft, leading to it being known by many as the "back-to-front" engine. This places

3828-476: The rest of the engine with its connections to the aircraft. This arrangement was patented by designer Newland, one of the original PT6 team. A similar general arrangement with a free-turbine power take-off at the exhaust end (the 1,000 shp (750 kW) P.181 engine) had been shown by Armstrong Siddeley Motors at the Farnborough Airshow in 1957. An early design improvement, incorporated in

3894-435: The type, multiple independent charter operators, such as British Eagle , were quick to adopt the Viscount into their fleets. During the 1960s, the Viscount formed the backbone of domestic air travel in Scotland. The early operational service of the Viscount quickly proved it to have significant performance advances over its rivals, and orders rapidly rose as a result; up to November 1952, only 42 aircraft had been ordered; by

3960-587: The updated SOCATA TBM -960 would be powered by the PT6E-66XT. The main variant, the PT6A , is available in a wide variety of models, covering the power range between 580 and 920 shaft horsepower (430 and 690 kilowatts ) in the original series, and up to 1,940 shaft horsepower (1,450 kilowatts) in the 'large' lines. The PT6B and PT6C are turboshaft variants for helicopters. In US military use, they are designated as T74 or T101 . Several other versions of

4026-434: Was Trans-Canada Air Lines (TCA), with a small fleet of Type 700 Viscounts. Initially, TCA was cautious of the Viscount due to the turboprop engine being a new technology, and a preference had existed for acquiring the piston-engined Convair CV-240 , instead; praise of the Viscount from pilots and a promise from Vickers to make any design changes desired by TCA persuaded it to procure the Viscount, instead. On 6 December 1954,

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4092-461: 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." Viscount cabin windows were huge ellipses, 19 by 26 inches. Viscount operational costs were lower than many rival aircraft; Vickers projected

4158-594: Was bought by American airlines in such quantity." TCA operated the Viscount for two decades until Air Canada (TCA relabelled with a name equally at home in English and French), ended Viscount services in 1974. The type was replaced by the McDonnell Douglas DC-9 . Routine Flight (1955) featured the TCA introduction of the Viscount in this National Film Board of Canada documentary. TCA's procurement of

4224-504: Was needed. Thus, pressurisation was required. The decision for pressurisation 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. Before the contract was signed, though, the government asked for the capacity to be increased to 32. This stretched

4290-693: Was the first scheduled airline flight by any turbine-powered aircraft. 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

4356-403: Was used as a test bed by Boulton Paul Ltd for the development of electronic flight-control systems. 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

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