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NASA’s Alternative Fuel Effects on Contrails and Cruise Emissions (ACCESS) experiment recently completed a series of tests that studied effects of alternate biofuel produced from camelina plant oil on engine performance, emissions and aircraft-generated contrails.

The tests involved flying a NASA Dryden Flight Research Center DC-8 airplane as high as 39,000 feet—an altitude typically flown by commercial airliners—while an instrumented HU-25C Guardian aircraft, based at NASA's Langley Research Center, trailed behind at distances ranging from 300 feet to more than 10 miles. Researchers measured exhaust composition and contrail characteristics depending on fuel type, plume duration and atmospheric conditions.

During the flights, the DC-8's four CFM56 engines were powered by conventional JP-8 jet fuel, or a 50-50 blend of JP-8 and an alternative fuel of hydroprocessed esters and fatty acids produced from camelina plant oil, NASA reported. More than a dozen instruments mounted on the Guardian jet characterized the soot, gases and ice particles streaming from the DC-8.

Dan Bulzan of the Cleveland, Ohio-based Glenn Research Center, who is the the ACCESS experiment’s technical lead, told Biomass Magazine that NASA purchased the biofuel from Honeywell UOP.

The ACCESS experiment follows two Alternative Aviation Fuel Experiment studies conducted in 2009 and 2011, during which ground-based instruments measured the DC-8's exhaust emissions as the aircraft burned alternative fuels while parked on a ramp in California.

An additional phase of ACCESS flights is slated for 2014, and the researchers plan to capitalize on lessons learned from previous tests and include a more extensive set of measurements.