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Neilster -> RE: Neilster's cool aerospace thing thread (6/25/2007 4:50:56 AM)
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I think one of the most interesting periods of aerospace history begins in the early 30s when many theoretical aerodynamic breakthroughs and engineering advances were being incorporated in new aircraft. This process was accelerated by WW2, by the end of which the gas turbine and swept wing heralded a new era. As a result, the mid to late 40s were a time of flux where designs were often quickly overtaken by the rush of new technologies. One such aircraft was the Bristol Brabazon... (from Wikipedia)
Development
In 1942, during World War II, the US and UK agreed to split responsibility for aircraft construction; the U.S. would concentrate on transport aircraft while the UK would concentrate on their heavy bombers. This would leave the UK with little experience in transport construction at the end of the war, so in 1943 a committee met under the leadership of Lord Brabazon of Tara in order to investigate the future needs of the British civilian airliner market.
The Brabazon Committee delivered a report, later known simply as the "Brabazon Report", calling for the construction of four of five general 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 miles (8,000 km), 225 foot (69 m) wing span, eight engines buried in the wings driving four pusher propellers, and enough fuel for transatlantic range. This "100 ton bomber" was in many ways the British analogue to the American Convair B-36. However the Air Ministry later changed their mind and decided to continue to pursue versions of the Avro Lancaster (leading to the Avro Lincoln) instead.
Only 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 exactly 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 (53.9 m) fuselage with 230 ft (70.1 m) wingspan (35 ft (11 m) more 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 was backward-thinking in one aspect however. When considering the people who would fly in the aircraft they designed, they thought in the context of wealthy people who were the only ones able to afford it at that point. The idea that a larger aircraft would make flying less expensive never appears to have occurred to them. Instead they 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 6 m³ (200 ft³) of room for every passenger, and 8 m³ (270 ft³) for luxury. This is about three times the interior room of a small car.
In order to meet these requirements the Type 167 initially specified a huge 25 foot (7.6 m) diameter fuselage, which is about 5 ft (1.5 m) greater than a 747, with upper and lower decks. This enclosed sleeping berths for 80 passengers, a dining room, 37 seat movie theatre, 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 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 movie theatre with a cocktail bar and lounge.
A tremendous amount of 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 tonnes 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 in itself. Bristol's factory in Filton was far too small to handle what was one of the largest aircraft in the world, and the local 2,000 ft (610 m) runway was too short to launch it. Construction of the first prototype's fuselage started in October 1945 in another hangar while a considerably larger assembly hall was built for final assembly and the runway was lengthened to 8,000 ft (2,440 m).
In 1946 it was decided to make the second prototype based on the Bristol Coupled Proteus turboprop engines instead of the less powerful Centaurus, increasing cruising speed from 260 to 330 mph (420 to 530 km/h) while reducing the empty weight by about 10,000 lb (4.5 t). This would be known as the Brabazon Mark II, which would be able to cross the Atlantic in a reduced time of 12 hours.
The Mk.I aircraft rolled out for engine runs in December 1948, and flew for the first time on 4 September 1949. Four days later it was presented at the Farnborough Air Show before starting testing in earnest. During 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.
By 1952 about £3.4m had been spent on development 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. In October 1953, after less than 400 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 Museum of Flight.
Although considered a failure and a white elephant, the record of the Brabazon is not all unfavourable. At least half of the money spent on the project was 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. 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 it had the best payload fraction of any aircraft up to that point, and 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. The Britannia is still considered by many[attribution needed] to be the ultimate propeller driven airliner.
I think the Brabazon is a fantastic looking aircraft and captures the optimistic, post-war mood of a time when aerospace technology seemed to have boundless potential.
I found an excellent, jaunty, period movie of it here (got to love the clipped, upper class accents of the English newsreel guys back then)...
http://www.youtube.com/watch?v=miRV-SgYx7Q
Cheers, Neilster
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