Bristol Brabazon

Brabazon

Picture - Brabazon in 1950

Role: Airliner
Manufacturer: Bristol Aeroplane Company
First flight: 4 September 1949
Retired: 1953
Status: Only example scrapped in 1953
Number built: 1

The Bristol Type 167 Brabazon was a large airliner, designed by the Bristol Aeroplane Company to fly transatlantic routes from the United Kingdom to the United States. The prototype was delivered in 1949, only to prove a commercial failure when airlines felt the plane was too large and expensive to be useful. Despite its size, comparable to a Boeing 767, it was designed to carry only 100 passengers, albeit in roomy conditions not generally found on modern aircraft. In the end, only a single prototype was flown; it was broken up in 1953 for scrap, along with an uncompleted second fuselage.

Design and development

Background

In 1943, a British government committee met under the leadership of Lord Brabazon of Tara to investigate the needs of the British civil airliner market.

The Brabazon Committee delivered a report, known as the "Brabazon Report", calling for the construction of four of five designs they had studied. Type I was a large transatlantic airliner, Type III a smaller airliner for the Empire air routes, and Type IV a jet powered 500 mph (800 km/h) airliner. The Type I and IV were considered to be very important to the industry, notably the jet powered Type IV which would give the UK a commanding lead in jet transports.

Bristol had already studied a large bomber design starting as early as 1937, but nothing had come of this. In 1942 the Air Ministry published a tender for a new super-heavy bomber design, and Bristol dusted off their original work and updated it for their newer and much more powerful Bristol Centaurus engines. This led to a design with a range of 5,000 mi (8,000 km), 225 ft (69 m) wing span, eight engines buried in the wings driving four pusher propeller installations, and enough fuel for transatlantic range. This "100 ton bomber" and designs from the other major manufacturers were in many ways the British analogues to the American Convair B-36. However in expectation of long development times, the Air Ministry later changed their mind and decided to continue development of the Avro Lancaster, (leading to the Avro Lincoln) instead.

Picture - Bristol Brabazon main undercarriage wheels

Bristol 167

A year later, the Brabazon Report was published and Bristol was able to respond with a slightly modified version of their bomber to fill the needs for the Type I requirement. Their earlier work was the sort of performance the Brabazon committee was looking for, and they were given a contract for two prototype aircraft. After further work on the design, a final concept was published in November 1944. It was for a 177 ft (54 m) fuselage with 230 ft (70.1 m) wingspan (35 ft/11 m greater than a Boeing 747) powered by eight Bristol Centaurus 18-cylinder radial engines nested in pairs in the wing. These drove eight paired contra-rotating propellers on four forward-facing nacelles.

The Brabazon Report assumed that the wealthy flying the plane would consider a long trip by air to be uncomfortable, and they designed the Type I for luxury, demanding 200 ft³ (6 m³) of room for every passenger, and 270 ft³ (8 m³) for luxury. This is similar to the interior room of a small car.

To meet these requirements the Type 167 specified a huge 25 ft (8 m)-diameter fuselage, which is about 5 ft (1.5 m) greater than a 747, with full-length upper and lower decks. This enclosed sleeping berths for 80 passengers, a dining room, 37-seat cinema, promenade and bar; or day seats for 150 people. The Committee recommended a narrower fuselage designed for 50 passengers. BOAC agreed, but preferred a design for only 25 passengers. An agreement with the airline eventually led to an interior layout housing a forward area with six compartments, each for six passengers and a seventh for just three; a mid-section above the wing - the wing was 6 feet deep at that point - with 38 seats arranged around tables in groups of four with a pantry and galley; and a rear area with 23 seats in an aft-facing cinema with a cocktail bar and lounge. Like the Saunders-Roe Princess, the Brabazon concept was a fusion of pre-war and post-war thinking, using highly advanced design and engineering to build an aircraft that was no longer required in the post-war world.

A tremendous effort was put into saving weight. The Type 167 used a number of non-standard gauges of skinning in order to tailor every panel to the strength required, thereby saving several tons of metal. The large span and mounting of the engines close inboard, together with structural weight economies, demanded some new measure to prevent bending of wing surfaces in turbulence. A system of gust alleviation was developed for the Brabazon, using servos triggered from a probe in the aircraft's nose. Hydraulic power units were also designed to operate the giant control surfaces. The Brabazon was the first aircraft with 100% powered flying controls, the first with electric engine controls, and the first with high-pressure hydraulics.

Building the aircraft was a challenge. Bristol's existing factory in Filton was too small to handle what was one of the largest aircraft in the world, and the 2,000 ft (610 m) runway was too short to launch it. Construction of the first prototype's fuselage started in October 1945 in an existing hangar while a gigantic hall for final assembly was built, whose designer, T. P. O'Sullivan, was awarded the Telford Premium for the work. The runway was lengthened to 8,000 ft (2,440 m), which required moving elsewhere the inhabitants of the village of Charlton.

Some design and construction work was shared out to other British companies such as Folland Aircraft.

Mark II

In 1946 it was decided to make the second prototype based on the Bristol Coupled Proteus turboprop engines - eight paired turboprops driving 4-bladed screws through a common gearbox.. This would increase cruising speed from 260 to 330 mph (420-530 km/h) and ceiling while reducing the empty weight by about 10,000 lb (4,540 kg). This Brabazon Mark II, would be able to cross the Atlantic (London-New York) in a reduced time of 12 hours.

Although the Proteus was slimmer than the Centaurus, the wing thickness was not to be reduced in the Mark II but the leading edge would be extended around the engines.

Changes to the wheel arrangement planned for the Mark II would have allowed it to use most runways on both the North Atlantic and Empire routes.

Testing

Picture - Bristol Brabazon G-AGPW takes off on its Maiden flight on 4 September 1949 at Filton Aerodrome

The Mk.I aircraft, registration G-AGPW, rolled out for engine runs in December 1948, and flew for the first time, over Avonmouth for 25 minutes, on 4 September 1949 captained by Bristol Chief Test Pilot Bill Pegg. It flew to about 3,000 ft (910 m) at 160 mph (257 km/h) and landed at 115 mph (185 km/h), throttling back at 50 ft (15 m). Four days later, it was presented at the Farnborough Airshow before starting testing in earnest. It was demonstrated at the 1950 Farborough Airshow with a take-off, clean configuration fly-past and a landing. In June 1950, she visited London's Heathrow Airport, making a number of successful takeoffs and landings, and was demonstrated at the 1951 Paris Air Show. By this point, BOAC had lost any interest in the design, if it ever really had any, and although some interest was shown by BEA on flying the prototype itself, various problems that would be expected of a prototype meant it never received an airworthiness certificate.

Cancellation

By 1952, about £3.4m had been spent on development (£53.4m in year-2000 pounds) and it showed no signs of being purchased by any airline. In March, the British government announced that work on the second prototype had been postponed. The cancellation of the project was announced by the Minister for Supply (Duncan Sandys) on 17 July 1953 in the Commons saying that it had given all the useful technical knowledge it could but with no interest from civil or the military they had no justification for continuing to spend money on it. About 6 million pounds had been spent and a further 2 would be required for the completion of the Mark II. The buildings and runway had cost a further £6 million. In October 1953, after 164 flights totalling 382 hours flying time, the first prototype was broken up, along with the uncompleted Mk.II prototype. All that remains are a few parts at the Bristol Industrial Museum and Scotland's National Museum of Flight.

Picture - Bristol Brabazon model

Although considered a failure and a white elephant, the record of the Brabazon is not entirely unfavourable. At least half of the large sums spent on the project were put into infrastructure, including the large hangars and runway at Filton. This meant that Bristol was now in an excellent position to continue production of other designs and the hall was used for building the Britannia aircraft. In addition, many of the techniques developed as a part of the Brabazon project were applicable to any aircraft, not just airliners.

Bristol had also won the contract for the "unimportant" Type III aircraft, which they delivered as the Bristol Britannia. Using all of the advancements of the Brabazon meant the Britannia had the best payload fraction of any aircraft up to that point, and it kept that record for a number of years. Although the Britannia was delayed after problems with the Type IV, the de Havilland Comet, it went on to be a workhorse for many airlines into the 1970s.

Specifications (Mark I)

Data from Flight

General characteristics

Crew: 6-12
Capacity: 100 passengers
Length: 177 ft (54.0 m)
Wingspan: 230 ft (70 m)
Height: 50 ft (15 m)
Wing area: 5,317 ft² (494.0 m²)
Airfoil: Root T.P.4 (mod) Tip T.P.5
Empty weight: 145,100 lb (65,820 kg)
Max takeoff weight: 290,000 lb (130,000 kg)
Powerplant: 8x— Bristol Centaurus radial engines, 2,650 hp (1,860 kW) each
Propellers: paired contra-rotating 3-bladed Rotol
Propeller diameter: 16 ft (4.9 m)
*Fuel capacity 13,650 Imp gal (61,971 L)

Performance

Maximum speed: 300 mph (260 kn, 480 km/h) at 25,000 ft
Cruise speed: 250 mph (220 kn, 400 km/h) at 25,000 ft
Range: 5,500 mi (4,800 nmi, 8,900 km) at 250 mph and 25,000 ft
Service ceiling: 25,000 ft (7,600 m) at full weight
Rate of climb: 750 ft/min () at sea level
Max wing loading: 54 lb/ft² (270 kg/m²)
Minimum power/mass: 0.073 hp/lb (120 W/kg)

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Source: WikiPedia