Lycoming Engines plans to sustain, support and improve gasoline-fueled aircraft piston engines for the immediate future, says Michael Kraft, senior vice president and GM of the company. It is cost-prohibitive for Lycoming to develop clean-sheet aircraft piston engines, so the company is testing its existing line-up to determine which models will run on the unleaded aviation and automotive fuels such as UL91 Avgas and 91 and 93 octane automotive gasoline.

Which models will run on unleaded fuels is “a matter of power density,” Kraft notes. Low-compression, relatively low-power-output models, such as the 108- hp to 115-hp O-235, are approved to use UL91 Avgas or 93 octane auto gas. Higher-horsepower engines—such as the

300-hp versions of IO-540 and TIO-540 engines that produce 350 hp—only can use legacy 100LL fuel. Notably, Lycoming’s new iE2 electronic engine management systems will reduce pilot workload, but won’t permit existing engines to use lower-octane fuels, Kraft says.

Kraft adds that modifying existing engines with direct injection or other advanced technologies would allow them to use a variety of gasoline fuels. But such modifications would require new FAR Part 33 engine type certifications, so the upgrades would be cost-prohibitive because the general aviation piston-aircraft market is shrinking, and there is no projected turnaround.

Leaded Avgas production is also declining, as Europe and other regions create economic disincentives. Avgas can be twice as expensive as Jet A in some regions, and is not available at all in other areas.

As a result, Avic-owned arch-rival Continental Motors is embracing turbo-diesel technology by acquiring Thielert’s assets and licensing design rights from Safran SMA Engines, rebranding the 230-hp SR305 engine as the TD-300. Lycoming is hedging its bet on gasoline-powered engines by inking a deal with Safran to provide support and parts distribution for the SR305, strengthening Cessna’s efforts to market its new SR305-powered Skylane JT-A. Consequently, Lycoming’s in-house turbo-diesel development programs are all but dead.