AIN Blog: Making the Move Away From 100LL

 - September 4, 2014, 12:37 PM
Pipistrel Alpha
This Pipistrel Alpha LSA runs much more happily on unleaded autogas. (Photo: John Jerabek)

One-hundred octane low-lead avgas (100LL) is on its way out. Despite the fact that studies by the Environmental Protection Agency have failed to demonstrate a clearly higher risk attributable to lead emissions by piston-engine 100LL-burning aircraft, lead is poisonous in any concentration. Enormous pressure is forcing the FAA to confront this issue, and someday, one must hope, a viable replacement fuel will be available.

For general aviation, the problem is that many aircraft cannot burn anything without the detonation-prevention capabilities of 100LL. Roughly 30 percent of all piston-powered aircraft have engines that require leaded avgas. These airplanes, and probably most piston-powered helicopters, will need a replacement fuel that meets the anti-detonation requirements and can be manufactured and distributed with processes not significantly more complex than those already in place.

The fact that 70 percent of the GA fleet can fly safely with ethanol-free unleaded autogas (mogas in aviation parlance), however, means that an interim solution is at hand, right now.

The biggest complaint about switching to a new fuel has less to do with its manufacturability and more to do with distribution. The entire distribution system is currently set up to handle 100LL, and that’s what all the avgas tanks and trucks at airports are capable of pumping. There are some airports with mogas tanks, but these are few and far between. If and when there comes a day when the aviation industry makes the switch to an alternative gasoline product that satisfies the needs of high-power engines, the distribution system needs to be ready to handle this fuel. Suddenly switching from avgas to another type of gas won’t be simple or quick.

This industry is stuck in a chicken-versus-egg conundrum. Nobody wants to invest in mogas tankage because there isn’t much of a market for mogas in aircraft. Yet the many aircraft that can use mogas have no efficient way to buy it.

The simple solution is to get ready for the transition now, by installing mogas-capable facilities at airports that serve aircraft that can burn mogas. At the very least, any FBO that has to right to deliver fuel at airports could purchase a small fuel truck to serve mogas. There actually is a mogas distribution network, and it is available to some degree, at handfuls of airports in many states. And the more that the fuel is available, the more pilots will use it. Certainly all the pilots flying light sport aircraft—thousands by some counts—would welcome the opportunity to buy mogas instead of 100LL, which still causes lead-fouling on spark plugs. Airport commissions and management should have zero concern about mogas, given that its use removes lead from the environment and makes their airports greener.

It’s true that many LSAs, especially those powered by Rotax engines, can burn autogas with up to 10 percent ethanol, which is what is for sale at the local gas station, but when we make the switch to a new alternative fuel, it very likely isn’t going to contain any alcohol.

Many other aircraft can quality for purchase of a supplemental type certificate (STC) from Petersen Aviation or the Experimental Aircraft Association and then legally and safely burn mogas. Some aircraft with engine-driven fuel pumps such as the Piper low-wings will require a new fuel pump, but most gravity-fed aircraft powered by low-compression engines qualify to install the STC without modifying the fuel system. According to Petersen, about 60,000 aircraft have been upgraded with mogas STCs and 115,000 certified airplanes qualify for the STC. That doesn’t include tens of thousands of experimental airplanes with engines that could run on mogas (for which an STC is not required).

If mogas were more widely available, more pilots would use it. And when the inevitable transition to a new aviation gasoline comes about, the distribution network and airport facilities could be ready. Let’s start making the switch now. Why waste any more time?