July 30, 2013 - Could the solution to the avgas crisis, the high cost of pilot training, concerns about lead emissions, and a host of other challenges facing general aviation be parked outside the Innovations Pavilion here at EAA AirVenture Oshkosh?
The 180-hp Aviat Husky with the bulbous belly tank unveiled here this week makes a compelling case for a cheap, abundant, non-polluting, but heretofore untried energy source for aviation that could solve these problems: compressed natural gas (CNG).
Among CNG's advantages over avgas: It's 138 octane, it's a much cleaner fuel, and it costs less than a dollar for the equivalent of 1 gallon of 100LL.
N15NG is the first dual-fuel, piston-powered aircraft to operate on both CNG and avgas. At the flick of a switch and the advance or retarding of the throttle the pilot can switch between the two fuel sources.
Developed by Aviat Aircraft of Afton, Wyoming, in association with Minneapolis-based Aviation Foundation of America (AFA), the Husky is capable of operating completely on CNG, but the current lack of refueling stations makes total reliance on CNG impractical.
AFA President Greg Herrick came up with the idea of trying to power an aircraft with CNG last year and approached Stu Horn, president and owner of Aviat Aircraft - which has a history of bringing innovation to general aviation, such as offering the first factory-installed enhanced vision system (EVS), and first inflatable seat belt restraints in a certificated aircraft.
The first question Horn asked himself: "Why would I want to do this?" he told AirVenture Today yesterday at the Aviat display at Exhibit 205-207/220-222. But after studying the increasing use of CNG for ground transportation and its abundance in the U.S., he concluded, "The answer was, 'Because I can.' I said, 'Let's do this.'"
Early this year Horn created a "dog team" of eight Aviat employees to work on the project along with outside CNG experts. The team created the hardware and software for the fuel controls; with the exception of these fuel controls and the belly tank, N15NG is a stock Husky.
The belly tank on N15NG holds the equivalent of 14 gallons of CNG, and the installation weighs about 135 pounds, including the 70-pound tank. But composite CNG tank technology is rapidly advancing; current generation tanks would weigh about 30 pounds less. As for the major drawback cited by many naysayers, the lack of refueling stations: "Everything begins with a first step," Herrick said.
"Think of a flight school where training flights are two hours. It will take the cost of fuel down 80 percent." And as for lack of distribution, CNG is delivered via pipeline throughout North America, and is even piped into many aircraft hangars, where it powers hot water heaters.
As for the lead many aircraft engines need to operate at peak efficiency, simply nickel plating the valves obviates the need for the additive.
Horn piloted N15NG to Oshkosh from Afton. He reports EGTs and CHTs run 30 degrees cooler with CNG than avgas, and until engines are redesigned to take advantage of its 138 octane, there's no difference in performance between the two fuels.
Said Herrick, "I want people to look at this and see this could really work and lower the cost of flying, and most importantly, lower the cost of flight training."
Horn, meanwhile, will meet with strategic partners here to discuss the CNG technology and "understand what their needs are. Based on that feedback," he said, "we'll formulate a plan for what comes next."