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Oil prices have tumbled, and the economy has elbowed the environment from the headlines, but aviation’s drive toward alternative fuels shows no sign of slowing down.

On Dec. 30, Air New Zealand conducted the first flight test of a second-generation biofuel blend. Continental Airlines on Jan. 7 and Japan Airlines on Jan. 30 will flight-test additional biofuel mixes that meet the airline industry’s criteria for environmental sustainability, which include not competing with food crops for resources.

Three biofuel flights in a month was unthinkable just two years ago, and these tests will generate much-needed data for those charged with rewriting the jet-fuel specification, for the first time in decades, so the aviation industry can pursue the economic and environmental promise of alternative fuel sources.

“Fuel prices may have fallen, but there’s no need to slow down,” says David Morgan, Air New Zealand’s general manager of airline operations and chief pilot. “There’s a finite resource of crude oil, and no point in putting off finding alternative sources,” he says, describing the test flight as “a step on the biofuel journey for the industry.”

The 2-hr. flight from Auckland over Hauraki Gulf involved a 50:50 blend of conventional Jet A-1 and a biofuel produced from vegetable oil extracted from jatropha, a plant that grows on arid and non-arable land. Jatropha oil for the test was sourced by Terasol Energy from India, Malawi, Mozambique and Tanzania and processed into jet fuel in the U.S. using refining technology developed by Honeywell company UOP.

The Air NZ test involved the left outboard No. 1 engine on a RB211-powered 747-400, and was the result of 18 months of work in partnership with Boeing, Rolls-Royce and UOP, says Morgan. The flight was preceded by extensive ground tests at Rolls. “By the time the biofuel was blended with Jet A-1 it was indistinguishable from normal jet fuel,” he says.

The flight involved a series of fuel-specific tests, beginning with a full-throttle takeoff and climb at varying thrust. Leveling off at 10,000 ft., the crew varied bleed loads on the engine. Then between 20,000-25,000 ft. a suction test was conducted to check fuel lubricity. Pumps in the tank were switched off and fuel drawn through the system using pumps on the engine.

“There was absolutely no change in performance,” says Morgan. “That’s what was notable about the flight – nothing happened; there were no surprises.” Climbing to 35,000 ft., the crew conducted two acceleration tests, rapidly closing then advancing the thrust lever at Mach 0.8 and 300 kt. to see if the engine would surge or flame out. “There was no issue,” he says.

After tests to check that other fuel-driven systems worked as expected, the engine was shut down and a windmill restart conducted at 25,000 ft., followed by a second shutdown and starter-assisted restart at 18,000 ft. A simulated approach and all-engine go-around was accomplished between 10,000-7,000 ft. in preparation for landing back at Auckland International Airport.

Full reverse thrust was used on landing and, after taxi back and shutdown, the biofuel-powered engine was immediately restarted to confirm it would start when hot. A blank flight data recorder was fitted before the test and downloaded afterward for analysis by Boeing and Rolls-Royce. The RB211 will be removed for inspection and the 747’s fuel system cleaned and checked before the aircraft is returned to revenue service, says Morgan.

“The purpose of the flight was to be a stepping-stone to the certification of jatropha,” he says. The test will provide data needed by the ASTM International subcommittee writing the new specification for drop-in alternatives to conventional jet fuels. “Jatropha is actually better than specification: it has a lower specific gravity, higher calorific value and lower freezing temperature – three good things for aviation.”

Jatropha was selected for the test because it was the most readily available biofuel feedstock meeting Air NZ’s sustainability criteria, although it is not expected to be available in commercial quantities for another two to three years. The airline also looked at algal oil, but it was not available within the timeframe of the test. “We may do an algae test,” he says.

Continental will test a biofuel made from algae and jatropha in a 50:50 blend with conventional jet. The algal oil has been sourced from open ponds in Hawaii by Sapphire Energy and refined using the same UOP processing technology as the jatropha. The test flight over the Gulf of Mexico will involve one engine on a CFM56-powered Boeing 737-800.

JAL will test a third biofuel mix – mostly camelina, but also jatropha and some algae – in a 50:50 blend with Jet A-1 in one engine on a Pratt & Whitney JT8D-powered 747-300. The camelina oil has been sourced in Montana by Sustainable Oils and processed using the same UOP technology. Camelina is used as a rotational crop and can grow on marginal land.

UOP plans to release its hydrotreatment technology for licensing by the middle of this year, and says it is talking to major agricultural companies as well as to fuel refiners about commercial-scale plants. The company estimates there will be sufficient feedstock and refining capacity to produce “hundreds of millions of gallons” of biofuel a year by 2012.

For aviation to benefit, biofuel blends first have to be certificated as drop-in replacements for conventional jet fuel, and ASTM’s aviation fuels subcommittee is making progress toward the approval of a new specification for synthetic fuels. The specification, dubbed DXXXX, is being structured to allow use of multiple alternative fuels, both non-renewable and renewable.

The draft specification was reviewed, but not approved, at an ASTM meeting in early December. Comments are being addressed and “there is good potential for approval of the DXXXX specification by the next ASTM meeting in June 2009,” states the Commercial Aviation Alternative Fuels Initiative (Caafi), which is led by the U.S. FAA.

As a first step, approval is being sought for blends of up to 50% synthetic fuel produced from coal, gas or biomass using the Fischer-Tropsch (FT) process. These are up for approval first because research data is available on candidate FT fuels, but Caafi’s view is that approvals are expected to follow for “hydrotreated renewable fuels and other alternatives as data from technical evaluations is obtained.”

For Air NZ, approval for jatropha and other biofuels is key to achieving its goal of becoming “the most environmentally sustainable airline,” says Morgan. While he expects biofuel will be used first on domestic flights, where the supply chain is simpler, the airline is prepared to be involved in refining biofuels to supply the region. “If it adds to Air New Zealand’s business and is good for New Zealand’s economy and environment, we would consider it.”