Fri 1 Feb 2008 – An Airbus A380 test aircraft has flown between Filton, UK and Toulouse, France with one of its four Rolls-Royce Trent 900 engines powered by an alternative, or synthetic, gas-to-liquid (GTL) jet fuel. This first ever flight by a commercial aircraft follows similar successful trials by the United States Air Force and just beats a test flight planned later this month by Virgin Atlantic using biofuel on a Boeing 747.
Shell International Petroleum provided the GTL jet fuel and the tests are running in parallel to the agreement signed at the Dubai Air Show last November with the Qatar GTL consortium partners (read story), who also include Rolls-Royce and Qatar Airways.
The A380 was chosen not only because of its modern technology, although Airbus says any of its models could have been used, but its four engines have segregated fuel tanks, making it ideal for engine shut down and re-light tests under standard evaluation conditions. During the flight, one engine was fed with the blend of GTL and ordinary kerosene jet fuel and the other three with conventional jet fuel. GTL, which looks like kerosene but is clear coloured, is a natural gas that has been cleaned and undergone the Fischer-Tropsch process. This process can convert coal, natural gas and other carbon-based feedstocks into petroleum substitutes.
The flight’s goal, says Airbus, was to see how the aircraft operated on GTL and to observe the engine’s behaviour as it was shut down and re-started in flight. Emissions will be compared with those of kerosene and the team will be using the results to predict the environmental benefits and define the next steps.
In researching alternative fuel, Airbus says it is looking for a ‘drop-in’ product, meaning that it could be used in aircraft currently in service. It would equal or better the aircraft performance while offering environmental benefits. Airbus is hoping to establish what the best alternative fuel options are and how they will benefit the environment. “As synthetic fuels are reported to have similar characteristics, whatever their original feedstock, this test was an excellent pre-cursor to research into biomass-to-liquid (BTL) fuels, should a suitable supply become available,” it says.
GTL could be available at certain locations to make it a practical and viable drop-in alternative fuel for commercial aviation in the short term. It has attractive characteristics for local air quality, as well as some benefits in terms of aircraft burn relative to existing jet fuel. For instance, says Airbus, it is virtually free of sulphur.
In order for an alternative fuel to qualify for commercial aviation, review and approval by the international Fuel Standards is a pre-requisite, points out Airbus, and it hopes this will be obtained for GTL by 2013.
A US Air Force C-17 airlifter completed a transcontinental flight on synthetic fuel in December and is currently ground testing the CFM56 engine, the most widely used engine in the world, using synthetic fuels. Although its motives are largely cost and strategic based, the USAF is hoping to meet half of its energy needs by 2016 with such fuels.
Sir Richard Branson’s Virgin Atlantic, in conjunction with Boeing and GE, is expected to conduct its own biofuel tests on a B747 flight between London and Amsterdam sometime this month (read story).
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