The USAF aims to certificate its entire fleet to use 50% Fischer-Tropsch blends by 2011, and is now looking for biofuel alternatives

Commercial carriers are not the only ones experimenting with biofuels. The US Air Force is expanding its alternative fuel development programme to include certification of two 50% bio­fuel blends in addition to coal and gas-based synthetic fuel efforts under way. The USAF is to issue a request for proposals for two biofuels in spring as it aims to meet half of its domestic fuel needs by 2016 with domestically produced alternative fuels that are no worse to the environment than conventional petroleum.

While testing continues at Ohio's Wright-Patterson AFB to certificate the USAF's entire fleet to use 50% Fischer-Tropsch blends by 2011, the service is also attempting to introduce many JP8 jet fuel supplements instead of relying on one source of alternative fuel, USAF Alternative Fuels Certification Office director Jeff Braun says.

Biofuel requirements include the chemical composition and performance of JP8 jet fuel. The fuel must also be sustainable and scaleable. The USAF is uninterested in fuels made from feedstocks that compete with food supply or require huge amounts of land for production, Braun says.

USAF refuelling 

Between 605,000 litres (160,000USgal) and 757,000 litres of each candidate will be needed, depending on which aircraft type is used in testing. Plans have not been finalised, but the Boeing C-17 is likely to be one of the aircraft types used, Braun says. It is yet to be seen how fuel suppliers react.

"The biofuel aspect is more attractive to industry, but when you start talking about available feedstocks, this country has a lot of coal, which lends itself to synthetics," he says.

Depending on how quickly biofuel is acquired, the USAF would like to start certification later this year, Braun says, noting that some fit-for-purpose-type and combustion-type testing has also been performed for some biofuels. Component testing and flight-testing is set to begin in the third or fourth quarter of this year, he says.

The USAF move follows three commercial airline biofuel demonstrations in December and January by Air New Zealand, Continental Airlines and Japan Airlines. While biofuel technology has been rapidly maturing, biofuels have always been a possibility for the USAF, says Braun, who thinks most people did not expect biofuels to progress so quickly.

His office will apply lessons learned from the Fischer-Tropsch effort to the biofuel programme.

Initial plans to certificate synthetic fuel for every aircraft type were found to be unnecessary, Braun says. Instead, the USAF will only certificate biofuel for the highest-performance aircraft, he says.


However, previous data collection does not necessarily translate to a shorter testing period. Testing of infrastructure, support equipment and toxicity will also be needed for the second-generation biofuels.

While the USAF readies for biofuel testing, work continues on the Fischer-Tropsch programme. However, Braun says it is unrealistic for his office to pursue a 100% Fischer-Tropsch fuel because synthetic fuels are too low in density. "I don't know if we'll go too much above 50%," he says.

In January in Dayton, Ohio, the USAF met energy suppliers, including makers of biofuel feedstocks such as camelina and algae, as well as funding sources, the Federal Aviation Administration and the Commercial Aviation Alternative Fuels Initiative (CAAFI).

The Departments of Energy and Agriculture were also in attendance as they plan to allocate up to $25 million in research and development funding for biofuels, including aviation fuels, as well as bioenergy and bio-based products through the US Food, Conservation and Energy Act passed last year.

With large government programmes and money available, the aviation industry now needs to have a comprehensive plan to attract more attention, CAAFI executive director Richard Altman says.

The meeting was designed as a way for those providing funding to see that they are contributing to the whole rather than duplicating efforts, making aviation a more desirable transport sector with which to work, Altman says.

That Dayton meeting was held at the base where the majority of Fischer-Tropsch testing is performed, and where Goodrich has a small team to connect with its own Sensors and Integrated Systems team in Vergennes, Vermont.

Goodrich says it has completed certification testing on the Bell UH-1, Boeing B-1B, RC-135, F-15, Lockheed Martin C-5B, C-130J and variants, F-16, F-22, Northrop Grumman B-2, and the Sikorsky CH-53 and UH-60. Aircraft yet to be certificated are the Boeing E-4 (747), 737, KC-10, Bell Boeing V-22 and Lockheed Martin F-35. Goodrich expects to complete testing by the end of the first quarter. "Some of the fuels have been tested as good to go, and on others we've seen some measurement anomalies at high temperatures," it says.

In November, Goodrich's contract through Universal Technology Corporation was renewed. The 50% Fischer-Tropsch fuel blend, provided by Shell, has had slightly different properties that caused occasional errors in tank readings, but software adjustments for that monitoring corrected the discrepancy.

Goodrich is the original equipment manufacturer of fuel measurement and management systems for nearly every aircraft in the USAF inventory. Under the contract any number of fuels can be looked at. The two other fuels the USAF has told Goodrich to expect is a 100% synthetic kerosene (SPK) and fuels from hydrogenated vegetable or animal oils (HXO).

So far the USAF is pleased with the outcome of its accelerating test schedule. On 14 January the latest test flight took off from Memphis with synthetic blends in each engine of a C-5.

On 8 August 2007, the Boeing B-52H was certificated on fuel made from natural gas, with the C-17 following in December of that year. Flight tests of the F-22 are complete, as are ground tests of its F119 engines at Pratt & Whitney's West Palm Beach facility in Florida, as are tests on the F-15 and KC-135.

Planning for synthetic fuel trials with the C-130 transport, Fairchild A-10 ground-attack aircraft and Northrop Grumman RQ-4 Global Hawk and General Atomics MQ-9 Reaper unmanned air vehicles are ongoing. Braun is hopeful that all will fly by summer, adding that another order for 1.7 million litres of synthetic fuel will be needed this year.

If the service is to meet its goal of powering half its domestic fuel needs with synthetic fuels by 2016, development of production facilities will need to rapidly accelerate. However, plans for the Fischer-Tropsch facility at Montana's Malmstrom AFB have been cancelled, where Montana coal would have been converted via the Fischer-Tropsch process into synthetic jet fuel by a private producer. The facility would have cost hundreds of millions of private dollars and the USAF says the fuel project could interfere with security and safety in what is a weapons storage area used by the 341st Space Missile Wing.

Source: Flight International