First Indication Is That Navy Hornet Can Fly on 'Green Fuel'

The Navy says it is one step closer to flying the "Green Hornet." Members of the NAVAIR Fuels team recently made a small, but very vital step toward changing the source of jet fuel the U.S. Navy uses.

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The team tested an F404 F/A-18 engine to determine if it could run on a jet fuel (JP-5) derived from a weed.

"This engine run was our first shot at certifying a JP-5 fuel derived from a renewable source," said Tony Cifone, director for the Propulsion & Power Department at the Naval Air Systems Command. "This is the first step on the road to the 'Green Hornet'."

The "Green Hornet" encompasses more than just a new source for jet fuel. It will eventually include upgrades and new technology to create a more fuel efficient F/A-18 Super Hornet. More tests will occur in the December-January timeframe on the F414, the engine for the Super Hornet. This test could be conducted either at NAS Patuxent River or at the General Electric facility in Lynn, Massachusetts.

Secretary of the Navy Ray Mabus pointed out during the Navy's Energy Forum held last week, that the "Green Hornet" is an important element in accomplishing his five Green Goals, which center around reducing the use of petroleum derived fuels and increasing the use of energy from renewable sources. The intent is to have the alternative fuels in operational use in the Hornet within three years of certification.

This first test on the F/A-18 Hornet engine proved that a renewable source of JP-5 can be used as a "drop-in" replacement for the current petroleum-based jet fuel. "The engine reacted the way we had expected," said NAVAIR's Rick Kamin, who is the Navy's Fuel Team Lead. "It did not know the difference." Likewise, the operators in the fleet will not know the difference, Kamin said as he emphasized the importance of the "drop-in" aspect of an alternative fuel.

Cifone said he anticipates the first actual flight of a Super Hornet fueled with a renewable fuel blended with the current JP-5 will occur next spring. "The eventual goal for the Navy is to be able to use fuels produced from non-petroleum sources without having to blend them with petroleum derived fuels," Kamin explained. "The 50/50 blend is a stepping stone on the path. We are using a walk before you run philosophy.

"Aircraft, since their inception, have been developed around petroleum based fuels. Although renewable fuels currently being tested have many similar properties to petroleum based fuels, they are not 100 percent the same. Blending is the near term solution to allow use of these fuels until on-going research provides a complete solution."

The tests the fuels team conducts to ultimately certify alternative fuels are the same for all fuels. The tests encompass standard chemistry, component and engine testing. The certification process is the same regardless of the source of the fuel. One of the unknown aspects of using a fuel derived from a non-petroleum source is how it would affect seals in the various systems.

Standard petroleum-based jet fuel contains aromatics, a class of ring-shaped hydrocarbon molecules that includes benzene and related solvents. Aromatics soak into the seals and make them swell, and ensure a tight fit against the metal. "Self-sealing fuel bladders, for example," Kamin said, "need aromatics to work properly."

The fuel used in the recent run of tests was created from the camelina plant, which is in the same family of plants as the mustard seed and rapeseed. It needs little water or nitrogen to flourish and can be grown on marginal agricultural soil. An important aspect of using camelina as a renewable source for fuel is that it does not compete with food crops.

Kamin said the Navy's goal is to certify as many alternative fuels derived from renewable sources as possible.

FMI: www.navy.mil