EDWARDS AIR FORCE BASE: A remotely-piloted aircraft completed a 32-hour flight test using an alternative fuel mixture here Nov. 23.
The 412th Test Wing’s Global Vigilance Combined Test Force’s Block 20 RQ-4 Global Hawk took off Nov. 22 and became the first RPA to fly using the Fischer-Tropsch Synthetic Paraffinic Kerosene fuel blended with regular JP-8 jet fuel.
The Fischer-Tropsch process is a set of chemical reactions that converts carbon-based materials into liquid hydrocarbons. Typically utilizing coal, natural gas or biomass as a feedstock, the resulting synthetic liquid is utilized as a petroleum substitute.
“The RQ-4 Global Hawk aircraft is the last platform to be certified to use SPK fuel,” said David Tangren, the Global Vigilance CTF lead flight systems engineer. “The Global Hawk marks the end of the Air Force-wide Fischer-Tropsch testing effort to certify all aircraft platforms.”
Maj. Gen. Ellen M. Pawlikowski, the Air Force Research Laboratory commander, visited from Wright-Patterson Air Force Base, Ohio, for a briefing on the SPK Global Hawk flight test. She acknowledged that this flight represented a large step toward implementation of future fuels and noted that the AFRL is developing a number of additional alternative fuels for potential Air Force use.
“This flight test represents the culmination of an effort the Air Force has had the last several years to be able to qualify our aircraft to use Fischer-Tropsch-based fuels,” General Pawlikowski said.
Specifically, the aircraft flew on a mixture of 25-percent coal-to-liquid fuel, 25-percent natural gas-to-liquid fuel and 50-percent JP-8.
Because the remotely-piloted Global Hawk flies upwards of 60,000 feet for long hours, and the way its fuel is stored and utilized, the data collected will provide data regarding how the SPK will perform in a remotely-piloted aircraft when exposed to extreme environments, Mr. Tangren said.
“The data we will be collecting is engine-stability data; compatibility with our environmental control system and aerodynamic performance of the aircraft using the alternative fuel,” Mr. Tangren said.
As with all flight tests involving alternative fuels, data will be collected to see how well the aircraft performs with the SPK, versus 100-percent JP-8. Very little, or preferably no difference, between performance indicates a successful test.
“We’ll compare the test results with the baseline JP-8 tests we conducted on the Global Hawk and, if both agree, we will certify the fuel for it,” said 1st Lt. Brian Palmer, a GBCTF Global Hawk Propulsion engineer.
Testing the fuel on an RPA marked one of the last requirements in certifying the use of the FT-derived SPK throughout the Air Force fleet. The SPK has been tested and certified for use in virtually every other Air Force system.
General Pawlikowski said this flight test is an important part of the Air Force’s security objectives. The service is looking at a three-pronged approach, which includes increasing the number of energy sources as well as decreasing the amount of foreign-sourced energy we currently use — ultimately changing the culture of the Air Force.
“The fuel used in the Global Hawk today is built from coal and natural gas,” General Pawlikowski said. “With the success of this flight, the next step will be to test fuels from renewable sources such as biomass. It will indicate we can use alternative fuels with the Global Hawk. Our next step will be to work with the commercial aviation industry to develop biomass fuels and test again to see if the Global Hawk can fly on renewable fuel resources. Our overall objective is to position the Air Force to get 50-percent of our fuel from environmentally-friendly, domestic-based sources by 2016.”
Air Force researchers are currently testing an alternative fuel derived from biomass. Known as hydrotreated renewable jet fuel, this fuel is made using animal fats and plant oils extracted from plants like camelina. Camelina is a weed-like plant not used for food and thrives with little cultivation. Fuel derived from this source has already been successfully tested at Edwards AFB on a C-17 Globemaster III.
Air Force officials note the quest for different alternative fuels is not a competition.
“The Air Force is not looking for a single winner, said Jeffrey Braun, the chief of the Air Force’s Alternative Fuels Certification Division. “The Air Force is trying to identify as many sources of supply — alternative sources of JP-8 — as possible. These fuels will be considered ‘drop-in fuels’ when blended with JP-8 and simply referred to as ‘JP-8.'”
The Global Hawk landed Nov. 23. While some of the performance test points were not completed due to high winds and turbulence at altitude, initial data indicates that the Global Hawk platform should have no significant issues utilizing the FT blend. An additional evaluation flight is scheduled in the coming weeks.
