The US Air Force's bid to reduce its dependence on foreign oil, which includes certificating a 50% blend of synthetic jet fuel and conventional JP-8 across its entire fleet of aircraft by early 2011, appears to be well on schedule.

Speaking at the Future Fuels Aviation Summit in London, Jeff Braun, director of the USAF's Alternative Fuels Certification Office, said testing of the Boeing F-15's Pratt & Whitney F100 engine is due to start on 26 April, with a test schedule of around 50-60h. General Electric F110 engine tests for the same aircraft will follow in October, he says, adding: "We are finding that based on our experience we can hit the points we want to hit within that timeframe."

 USAF F-15 in flight
 © US Air Force

P&W will start testing the Lockheed Martin F-22's F119 engine in May, or possibly June, with Braun expecting flight tests to conclude in the autumn. "Every aircraft that the USAF flies is at some point in the process," he adds.

The P&W TF33-powered Boeing B-52H bomber last August became the first type to be approved, and ground and flight test demonstrations of the Boeing C-17 transport's P&W F117 using a gas-to-liquid (GTL) synthetic fuel supplied by Shell Malaysia are also complete.

Despite some initial concern from P&W over corrosion, Braun expects formal certification this summer - something that could act as a bridge to commercial aviation use. "It looks like their concerns are not valid, and now they are ready to support that fuel in that engine," he says.

GE, meanwhile, is close to reaching 50h of ground testing with the Boeing B-1B bomber's F101 powerplant, with early indications showing practically identical engine performance using the GTL synthetic fuel, with a slight increase in thrust and slightly reduced specific fuel consumption. Braun says the aircraft (pictured below during testing at Dyess AFB, Texas) performed equally in all stages of its flight profile, including supersonic and low-level, high-speed operations, and that the mission commander reported he "would take this aircraft into combat tomorrow".

© US Air Force

Following certification of the entire USAF fleet to use synthetic fuel by 2011, Braun says "the next target will be what we call the "tipping point", where we will look at increasing the synthetic mix and the point where engine performance deteriorates." Work will be conducted by the Air Force Research Laboratory.