Thursday, October 8, 2009

Bristol Britannia

Bristol Britannia

Type 175 Britannia

Royal Air Force Bristol Britannia Spica in 1964.
Bristol Aeroplane Company
First flight
16 August 1952
Primary users
British Overseas Airways Corporation

Royal Air Force
Number built
Canadair Argus

Canadair CL-44
The Bristol Type 175 Britannia was a British medium/long-range airliner built by the Bristol Aeroplane Company in 1952 to fly across the British Empire. Soon after production the turboprop engines proved susceptible to inlet icing and two prototypes were lost while solutions were found. By the time it was cleared, jets from France, UK and the US were about to enter service and only 85 Britannias were built before production ended in 1960. Nevertheless, the Britannia is considered the high point in turboprop design and was popular with passengers, earning itself the title of "The Whispering Giant" for its quiet and smooth flying.


In 1942, during the Second world War, the US and UK agreed to split aircraft construction; the US concentrating on transport aircraft, and the UK on heavy bombers. This left the UK with little experience in transport construction at the end of the war, so in 1943, a committee under Lord Brabazon of Tara, investigated the future of the British civilian airliner market. The Brabazon Committee called for four main types of aircraft.

Bristol won the Type I and Type III contracts, delivering their Type I design, the Bristol Brabazon in 1949. The initial requirement for the Type III, Specification C.2/47, was issued by the Minister of Supply for an aircraft capable of carrying 48 passengers and powered with Bristol Centaurus radial engines. Turboprop and compound engines were also considered, but they were so new that Bristol could not guarantee the performance specifications. After wrangling between the Ministry of Supply and British Overseas Airways Corporation (BOAC) over costs, the go-ahead was given in July 1948 for three prototypes, although the second and third were to be convertible to Bristol Proteus turboprops.

In October, with work already underway, BOAC decided that only a Proteus-engined aircraft was worth working on, and the project was redrawn to allow both turboprop and piston aircraft. BOAC purchased options for 25 aircraft on 28 July 1949, to be powered initially with the Centaurus engine but to be re-fitted with the Proteus when available. The design was now aimed at long-haul Empire and trans-Atlantic routes rather than the medium haul Empire routes originaly planned and had grown to accomodate 83 passengers.

By the time the first prototype, registered G-ALBO, first flew on 16 August 1952 at Filton, BOAC and Bristol had dropped the Centaurus because the turboprop Proteus had shown such promise. The Britannia was now a 90-seater and BOAC ordered 15 of these Series 100s. In 1953 and 54, three de Havilland Comets disappeared without explanation, and the Air Ministry demanded the Britannia undergo lengthy tests. Further, delays were caused by engine problems, mostly related to icing and the loss of the second prototype G-ALRX in an accident caused by a failed engine in December 1953. This delayed the in-service date until February 1957, when BOAC put their first Britannia 102s into service on the London to South Africa route, with Australia following a month later.

Bristol then upgraded the design as a larger transatlantic airliner for BOAC, resulting in the Series 200 and 300. The new version had a fuselage stretch of 10 ft 3 in (3.12 m) and upgraded Proteus engines, and was offered as the all-cargo Series 200, the cargo/passenger (combi) Series 250, and the all-passenger Series 300.

The first public service was operated on the 1 February 1957 with a BOAC flight between London and Johannesburg. By August 1957 the first 15 Series 102 aircraft had been delivered to BOAC.  The last ten aircraft of the order were built as Series 300 aircraft for transatlantic operations.

The first 301 flew on 31 July 1956. BOAC ordered seven Model 302s but never took delivery - instead they were taken on by airlines including Aeronaves de México and Ghana Airways. The main long-range series were the 310s, of which BOAC took 18 and, after deliveries began in September 1957, put them into service between London and New York. The 310 series (318) also saw transatlantic service with Cubana de Aviación starting in 1958. In total 45 Series 300s were built, the first jet-powered, albeit in turboprop form, airliner to enter regular non-stop transatlantic service in both directions.

A further 23 Model 252 and 253 aircraft were purchased by the RAF, as the Britannia C.2 and C.1 respectively. Those in RAF service were allocated the names of stars, "Arcturus", "Sirius", "Vega" etc. The last retired in 1975, and were used by civil operators in Africa, Europe and the Middle East into the late 1990s.

Most aircraft were built by Bristol at Filton Aerodrome but 15 were built at Belfast by Short Brothers and Harland.

A licence was also issued to Canadair to build a maritime reconnaissance aircraft , the Canadair Argus and long-range transport, the Canadair Yukon. Unlike the Britannia, the Argus was built for endurance, not speed, and used four Wright R-3350-32W Turbo-Compound engines which use less fuel at low altitude. The unpressurized interior was left with almost no room to move, packed with sensors and weapons. Canadair also built 37 turboprop Rolls Royce Tyne-powered CL-44 variants for the civil market similar those built for the RCAF in CC-106 Yukon guise, most of which were used as freighters. Four were built as CL-44-Js had their fuselages lengthened, making them the highest capacity passenger aircraft of the day, for service with the Icelandic budget airline Loftleiðir. One, a modified Guppy version, remains airworthy, but not flying. Several were built with swing-tails to allow straight-in cargo loading.

General characteristics
  • Crew: 4-7
  • Capacity: 139 passengers (coach class)
  • Length: 124 ft 3 in (37.88 m)
  • Wingspan: 142 ft 3 in (43.36 m)
  • Height: 37 ft 6 in (11.43 m)
  • Wing area: 2,075 ft² (192.8 m²)
  • Empty weight: 86,400 lb   (38,500 kg)
  • Max takeoff weight: 185,000 lb (84,000 kg)
  • Powerplant: 4× Bristol Proteus 765 turboprops, 4,450 ehp (3,320 kW) each
  • Maximum speed: 397 mph (345 knots, 639 km/h)
  • Cruise speed: 357 mph (310 kn, 575 km/h) at 22,000 ft (6,700 m)
  • Range: 4,430 mi (3,852 nmi, 7,129 km)
  • Service ceiling: 24,000 ft ] (7,300 m)

Bell X-5

Bell X-5

Research aircraft
Bell Aircraft Corporation
Designed by
Robert J. Woods
First flight

20 June 1951

December 1958
Primary users
United States Air Force

National Advisory Committee for Aeronautics
Number built
Developed from
Messerschmitt P.1101
The Bell X-5 was the first aircraft capable of changing the sweep of its wings in flight. It was inspired by the untested wartime P.1101 design of the German Messerschmitt company. In contrast with the German design which could only be adjusted on the ground, the Bell engineers devised a system of electric motors to adjust the sweep in flight.

The incomplete Messerschmitt P.1101 fighter prototype recovered by US troops in 1945 from the experimental facility at Oberammergau, Germany, was brought back to the United States. Although damaged in transit, the innovative fighter prototype was delivered to the Bell factory at Buffalo, New York where company engineering staff studied the design closely and led by Chief Designer Robert J. Wood, submitted a proposal for a similar design.

Although superficially similar, the X-5 was much more complex than the P.1101, with three sweep positions: 20°, 40°, and 60°, creating an in-flight "variable-geometry" platform. A jackscrew assembly moved the wing's hinge along a set of short horizontal rails, using disc brakes to lock the wing into its in-flight positions. Moving from full extension to full sweep took less than 30 seconds. The articulation of the hinge and pivots partly compensated for the shifts in center of gravity and center of pressure as the wings moved.

Even so, the X-5 had vicious spin characteristics arising from the aircraft's flawed aerodynamic layout, particularly a poorly positioned tail and vertical stabilizer, which in some wing positions, could lead to an irrecoverable spin. This violent stall-spin instability would eventually cause the destruction of the second aircraft and the death of its Air Force test pilot in 1953.

The unfavorable spin characteristics also led to the cancellation of tentative plans by the US Air Force to modify the X-5's design into a low-cost tactical fighter for NATO and other foreign countries.

Two X-5s were built (50-1838 and 50-1839). The first was completed 15 February 1951, and the two aircraft made their first flights on 20 June and 10 December 1951. Almost 200 flights were made at speeds up to Mach 0.9 and altitudes of 40,000 ft (12,200 m). One aircraft was lost on 14 October 1953, when it failed to recover from a spin at 60 degree sweepback. USAF Captain Ray Popson died in the crash at Edwards Air Force Base. The other X-5 remained at Edwards and continued active testing until 1955, and remained in service as a chase plane until 1958.

The X-5 successfully demonstrated the advantage of a swing-wing design for aircraft intended to fly at a wide range of speeds. Despite the X-5's stability problems, the concept was later successfully implemented in such aircraft as the F-111, F-14 Tomcat, MiG-23, Panavia Tornado and B-1 Lancer.


The sole surviving X-5 is now at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio. It was delivered to the Museum in March 1958. It is displayed in the Museum's Research & Development Hanger.

General characteristics
  • Crew: 1
  • Length: 33 ft 4 in (10.1 m)
  • Wingspan:
    • Unswept: 33 ft 6 in (10.2 m)
    • 60° sweep: 20 ft 10 in (6.5 m)
  • Height: 12 ft (3.6 m)
  • Wing area: 175 sq. ft. (16.26 m².)
  • Empty weight: 6,336 lb (2,880 kg)
  • Max takeoff weight: 9,980 lb (4,536 kg)
  • Powerplant: 1× Allison J35-A-17 turbojet, 4,900 lbf (21.8 kN)
  • Maximum speed: 716 mph (1,150 km/h)
  • Range: 750 mi (1,207 km)
  • Service ceiling: 49,900 ft (15,200 m)

The Viscount

The Viscount was a British medium-range turboprop airliner first flown in 1948 by Vickers-Armstrongs, making it the first such aircraft to enter service in the world. It would go on to be one of the most successful of the first-generation post-war transports, with 445 being built.

The design resulted from the Brabazon Committee's Type II design, calling for a small-sized medium-range pressurised aircraft to fly its less-travelled routes, carrying 24 passengers up to 1,750 mi (2,816 km) at 200 mph (320 km/h).[1] British European Airways (BEA) was involved in the design and asked that the plane carry 32 passengers instead, but remained otherwise similar. During development, Vickers advocated the use of turboprop power, believing piston-engines to be a dead-end in aviation. The Brabazon committee was not so convinced, but agreed to split the design into two types, the Type IIA using piston power, and the Type IIB using a turboprop. Vickers won the IIB contracts, while the IIA was the Airspeed Ambassador.

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 Rolls-Royce Dart engines providing a cruising speed of 275 mph (443 km/h). An order for two prototypes was placed in March 1946, and construction started almost immediately. Originally to be named Viceroy, the name was changed after the partition of India in 1947. There was some work on replacing the Darts with the Armstrong Siddeley Mamba, but this was dropped by the time the prototypes were reaching completion.
The prototype Type 630 flew on 16 July 1948. It was awarded a restricted Certificate of Airworthiness on 15 September 1949, followed by a full Certificate on 27 July 1950, and placed into service with BEA the next day to familiarize the pilots and ground crew with the new aircraft. However 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.
The second prototype Viscount was named the Type 663 and was built as a test-bed. This aircraft fitted with two Rolls-Royce Tay (turbojet) engines and first flew in RAF Markings as VX217 at Wisley on 15 March 1950. It demonstrated at the Farnborough SBAC Show in September and was later used in the development of powered controls for the Valiant bomber. Subsequently, Boulton Paul Ltd used it as a test bed for electronic control systems until scrapping in the early 1960s.
General characteristics
  • Crew: Two pilots + cabin crew
  • Capacity: 75 passengers
  • Length: 85 ft 8 in (26.11 m)
  • Wingspan: 93 ft 8 in (28.56 m)
  • Height: 26 ft 9 in (8.15 m)
  • Wing area: 963 ft² (89 m²)
  • Empty weight: 41,479 lb (18,815 kg)
  • Max takeoff weight: 72,281 lb (32,786 kg)
  • Powerplant: 4× Rolls-Royce Dart RDa.7/1 Mk 525 turboprop, 2,100 shp (1,566 kW) each
  • Maximum speed: 352 mph (566 km/h)
  • Range: 1,735 mi (2,790 km)
  • Service ceiling: 25,000 ft (7,620 m)
  • Wing loading: 75 lb/ft² (368 kg/m²)
  • Power/mass: 0.12 hp/lb (0.19 kW/kg)

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