Michael Friend is a regular contributor to CONTACT! Magazine. He received his B.Sc.AAe from the University of Illinois in 1978. Work experience is varied and extensive in the aircraft design arena throughout the world. A commercial pilot and instructor, instrument rated, land and seaplanes as well as gliders, Michael is also the author of several published articles on light aircraft design. Presently, Michael is the Chief Engineer, Future Platforms, Preliminary Design for Boeing in Seattle, Washington, USA. You can read his other CONTACT! Magazine articles in issue #76 and issue #79. 

The recent past has seen some progress in the powerplants that we all depend upon to pull along (or push) our favorite aircraft. For decades, we were stuck in a rut in which 1930s technology was a given for light aircraft, with antiquated induction, ignition, combustion, and exhaust being the norm. In this article, we’ll take a look at the emerging trends and try to look forward to, say, the year 2025 to see what kind of motive power will be the norm. Automotive based? Hybrids? Alcohol fuel? Diesel? Fuel cells?  

SOME BACKGROUND
As a kid, my favorite powerplant was the Lycoming O-360. I would dream away the time in boring university lectures thinking about the exciting airplane I could design around this powerful and reliable engine. Let’s have a look at it-

While the picture is that of a 2005 production example, in fact it would have looked the same thirty years ago when I was doodling airplane designs in my physics notebook. If you were to compare a modern automotive engine to one from thirty years ago, the differences would be staggering. The reliability and efficiency of auto engines has grown by leaps and bounds, while aircraft engines have stayed the same. Why is this? The economy of scale is a

big driver, as the general aviation market is a lot smaller and makes it harder to absorb big research and development costs for new engine technology. Another factor is that progress in light-airplane engines has not been driven by government regulation in the same way that automotive engines have. While we all love to slam government regulation, in fact it is the imposition of emissions and fuel consumption regulations that has driven the frenzy of automotive engine development over the last thirty years.  

US GOVERNMENT REGULATIONS
Government regulation and free-market forces may well initiate a new round of development in aviation engines. For decades, lead has been eliminated from almost all fuels used in transportation. The only reason aviation has been exempt in the US is that the FAA has held sway over aviation fuels. That has now changed, and it seems likely that the US Environmental Protection Agency (EPA) will take an active role in avgas as well. I suspect we will see a move toward unleaded fuels across the board, with groups like the EAA and AOPA pressing for a uniform high-octane unleaded mogas that can be used in the majority of existing aircraft engines. Market forces will come into play as avgas becomes an annoyance for the small number of refineries that produce it today.

ALTERNATIVE FUELS?
What about using alcohol in today’s engines? You may have recently seen the news that the Brazil has certified a crop-duster, the Neiva Ipanema, for use with alcohol.

Brazil has been a leader in using biofuels made from indigenous crops. In addition, a group of RV-3’s from North Dakota was flown on alcohol fuel for years, appearing at airshows as the Vanguard Squadron. The use of this fuel is quite straightforward, requiring only minor changes in the carburetor and fuel system. The real issue with alcohol fuel is politics and infrastructure. It costs more to brew up a gallon of alcohol fuel than avgas so it comes down to government policy and tax credits to make it a market reality. The infrastructure for handling alcohol fueling at airports would take a bit of doing and I suspect that it won’t happen without a big push from governments.