In the interest of diversifying its fuel supply, the U.S. Air Force has been testing and certifying engines to run on a mixture of conventional jet fuel and biofuels derived from plants. Last month, testing began on a GE F110 using a 50/50 blend of the two fuels at the Arnold Engineering Development Center at AFB in Tennessee. This represents the first USAF dedicated testing of hydro-processed renewable jet (HRJ) blended fuel in an altitude chamber. The data gained from testing will be used to support a flight-test program on the F-22, C-17 and potentially the F-15. Test parameters to be measured include ignition light-off, throttle transients, augmenter (afterburner) lighting and screech and rumble monitoring to detect combustion instabilities.

The testing so far has focused on the F110 and Pratt & Whitney’s F100, as they are the most challenging and most fleet-representative engines in the USAF inventory. The USAF’s ultimate goal is to have complete certification of its engine fleet for unrestricted use of the HRJ blended fuel by the end of 2012. It also aims to supply half of its fuel requirements by 2016 with fuels produced domestically. Similar testing has been ongoing at Wright-Patterson AFB since 2008 to certify the entire fleet to use coal and gas-based blended fuel produced through the Fischer-Tropsch process.