F-15 Engine Tested On Tri-Fuel Blend

An F-15 Eagle engine is undergoing performance testing at Arnold Air Force Base in Tennessee using a unique blend of three different fuel types. The F100 engine is being tested with a combination of JP-8 conventional aviation fuel; a biofuel derived from tallow, which is an animal fat; and a synthetic fuel derived from coal through a process commonly known as Fisher-Tropsch.

File Photo Courtesy U.S. Air Force

The fuels testing is being conducted to ensure the different fuels, in varying combinations, are suitable for an upcoming series of F-15 flight tests tentatively scheduled for October at Eglin Air Force Base, FL, said Brian Knack, the Aerospace Testing Alliance's program engineer for the test. ATA is the operating contractor at the Arnold Engineering Development Center. "This (first phase of the test) evaluated a 50 percent (by volume) tallow-derived fuel, while the final phase is bringing Fischer-Tropsch-derived fuel together with the bio-fuel forming yet another new and unique blend," he said.

Testing has simulated the overall engine conditions experienced at near sea-level conditions. A baseline test using JP-8 was performed in the first phase of the test program. Then, a blend of 50 percent tallow-derived fuel and 50 percent JP-8 was evaluated. Finally, a blend of 25 percent tallow-derived fuel and 25 percent synthetic fuel and 50 percent JP-8 was evaluated.

"They've engineered these alternative fuel blends, both the tallow and FT, to meet the existing JP-8 (specifications) requirements," Knack said. "So, we're just verifying that, although it's within the same specification chemically, that it doesn't adversely affect engine performance."

Second Lt. Drew Miller, the AEDC's project manager for the test, pointed out that this entry is not a certification test series per se, nor is it  intended to include an analysis of "wear and tear" on the engine. "We'rejust demonstrating that the engine can successfully perform on the biofuels that we're testing," he said.

File Photo Courtesy U.S. Air Force

Engineers from the Air Force Alternative Fuels Certification Office at Wright-Patterson AFB, OH, noted that the hydro-treated renewable jet biofuels -- currently only available in research and development quantities -- are expensive. The expectation is that once they are certified for use by the Air Force and by airlines participating in the Commercial Aviation Alternative Fuels Initiative, industry producers will respond to the market demand and prices will fall in line with conventional jet fuel.

Lieutenant Miller said it's important to view this test from a wider perspective. "The Secretary of the Air Force has an initiative to reduce our dependence on oil (by) 50 percent by 2016, and this is just leading the way to make that happen," he said. "The Air Force is the largest oil consumer in the Department of Defense, and this is a major step towards increasing our independence."

Knack said he is already looking toward the future of bio-fuels. "This is the next step of biofuel evolution, and a couple years from now we could be running algae-based fuels or whatever is deemed to be the most efficient, economically produced on a mass production level," he said. "Then we will probably see it here."

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