An RQ-4 Global Hawk completed a 32-hour flight test using an alternative fuel mixture last week, according to the Air Force.
A Block 20 Global Hawk took off from Edwards AFB, Calif., at 4:30 p.m. Nov. 22 and became the first remotely piloted aircraft to fly using the Fischer-Tropsch Synthetic Paraffinic Kerosene fuel and regular JP-8 jet fuel blend, Air Force public affairs said.
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 aircraft landed cleanly at 11:06 p.m. on Nov. 23. While some of the performance test points were not completed due to high winds and turbulence at altitude, the Air Force said initial data indicate the platform should have no significant difficulties utilizing the Fischer-Tropsch blend. An additional evaluation flight has been scheduled for the coming weeks.
The RQ-4 Global Hawk aircraft is the final Air Force platform to be certified to use SPK fuel, said David Tangren, the flight systems engineer for last week’s test. “The Global Hawk marks the end of the Air Force-wide Fischer-Tropsch testing effort to certify all aircraft platforms,” he said.
Maj. Gen. Ellen Pawlikowski, Air Force Research Laboratory commander, said the flight represents a major step toward wider Air Force use of alternative fuels.
“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,” said Pawlikowski.
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 upward of 60,000 feet for long hours, the data collected will provide insight into how the SPK will perform in extreme environments.
“The data we will be collecting is engine-stability data,” said Tangren. He added that the Air Force is also collecting information about “compatibility with our environmental control system and aerodynamic performance of the aircraft using the alternative fuel.”
Comparisons between SPK and 100-percent JP-8 will also be analyzed.
“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, GBCTF Global Hawk propulsion engineer.
Further, Pawlikowski said the air service is taking a fresh approach to fuel usage that includes increasing the number of energy sources, as well as decreasing dependence on foreign-sourced energy.
“The fuel used in the Global Hawk today is built from coal and natural gas,” said Pawlikowski. “With the success of this flight, the next step will be to test fuels from renewable sources such as biomass.”
The Air Force then plans to work with the commercial aviation industry to develop biomass fuels.
“Our overall objective is to position the Air Force to get 50-percent of our fuel from environmentally-friendly, domestic-based sources by 2016,” said Pawlikowski.
The Air Force is 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. The camelina plant 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 on a C-17 aircraft.
“The Air Force is trying to identify as many…alternative sources of JP-8 as possible,” said Jeffrey Braun, chief of the Air Force’s alternative fuels certification division. “These fuels will be considered ‘drop-in fuels’ when blended with JP-8 and simply referred to as ‘JP-8.'”