In the not-too-distant future aircraft carrier deck refueling personnel or “purple shirts” as they’re commonly known, may be gassing up F/A-18 Super Hornets and other carrier aircraft with a biofuel blend derived from weeds.
The purple shirts won’t be the only personnel handling veggie gas if the service meets goals set forth by Secretary of the Navy Ray Mabus in October of last year. Among other objectives, Mabus wants an operational “green” carrier strike group to run on a significant percentage of biofuels by 2016, with a carrier group demonstration scheduled as early as 2012. Making that happen will require certification of an array of Navy platforms and power plants. The service is off to a good start with the General Electric F414-GE-400 which powers the F/A-18 Super Hornet.
Since early spring, the Navy has been test flying an F/A-18F Super Hornet at NAS Patuxent River in Maryland with a 50/50 blend of conventional jet fuel (JP-5) and a biofuel based on the camelina plant. A member of the mustard family, a distant relative of canola, and a short-seasoned, fast-growing crop, camelina is one of several plant sources being considered for biofuel production.
The first flight in the “Green Hornet” test program took place on April 22 (Earth Day) and a subsequent 15 flights have been made, totaling 17.5 hours flight time. Air Test and Evaluation Squadron VX-23, which carried out the flights, and the NAS Patuxent River-based Navy Fuels Laboratory are still reviewing the data, but all indications are the GE-F414 will be certified to run on the blend.
“Everything performed spectacularly,” Navy Fuels Team Leader Rick Kamin reported. “The aircraft performed exactly the same with the fuel [tested] in this program as with the conventional fuel.”
That sentiment was evident from the first 45 minute flight, after which test pilot Lt. Cmdr. Tom Weave commented, “The aircraft flew exactly as we expected – no surprises. The fuel works so well all I needed to do was just fly the plane.”
Naturally, considerable forethought and analysis facilitated what appears to have been a smooth test program. “The camelina fuel was a representative example of an entire family of plant oils that are hydro-processed into a finished product,” Kamin said. “Camelina was selected through open competition conducted by the Defense Energy Support Center (DESC) which buys all the fuel for DoD and the government. We listed the requirements and they ran the open procurement. Camelina was the fuel that could meet our requirements and delivery schedule.”
Sustainable Oils of Seattle, Wash., and Bozeman, Mont., provided 40,000 gallons of the camelina blend for evaluation at a cost $2.7 million. That comes to about $67.50 per gallon, but such small R&D batches of fuel are not representative of the potentially much cheaper costs of commercial quantities of biofuel. As importantly, whatever biofuels are ultimately to power the Navy’s tactical jet fleet and other platforms must be “drop-in” replacements for conventional fuel.
“Our primary goal is that any alternative fuel we approve, whether it be camelina, algae, or something else, must be a finished product that is a drop-in replacement for petroleum,” Kamin said. “The [camelina blend] is a hydrocarbon pretty similar to what we use today. That’s the difference between these biofuels and the biodiesels that are on the market. The biodiesels are oxygenated compounds so there is a piece of them which isn’t the true hydrocarbon we require in our systems. With camelina we won’t have to modify any of our aircraft or ship systems. We don’t change our distribution system and these fuels are 100 percent interchangeable.”
Though final analyses have yet to be completed, throughout the Green Hornet test program the camelina blend proved its suitability as a direct substitute for JP-5. “At this point in time, nothing negative has come up,” the Navy Fuels Team Lead confirmed. “There have been no issues.”
The blend is “water white,” the same color as many jet fuels, which can run the spectrum from white to yellow. From a handling standpoint, the camelina blend is treated just as any hydrocarbon fuel, and is no less, or more, safe. Kamin said its pumping flow rate is the same as conventional fuel. And its storage stability, tolerance to seawater compensation, resistance to biocontamination and flashpoint characteristics appear to be sufficient. The camelina blend is even more nasal-friendly than JP-5.
“As far as the smell, it’s not as pungent as petroleum fuel because these hydrogen-renewable jet fuels or diesel fuels have no aromatic compounds in them,” Kamin explained.
The biofuel has also shown no discernible affect on aircraft engine components or materials. “We did a bore scope analysis to the engine before the program and after the program and there was no abnormality,” Kamin said.
Nor was there any difference in dynamic performance. The Green Hornet F/A-18F was flown to multiple supersonic test points on the blend with no problems. “All the test pilots involved in the program came back from their flights with pretty much the same statement,” Kamin said. “If you didn’t tell them they were flying a 50-50 blend of biofuel and petroleum, they wouldn’t have known.”
This summer, Green Hornet program data will be reviewed to determine what other systems can be certified based on similarity and what systems will require additional testing. That testing will go forward in the upcoming fiscal year.