Editor’s Log

There is a moment in every homebuilt project when the airplane stops being a collection of parts and starts becoming a real machine. It usually happens when the engine arrives. Until then, the fuselage on sawhorses is a promising sculpture. The day you uncrate the powerplant and set it on the bench next to the firewall, the project acquires a genuine pulse. 

Everything that follows—the mount, the baffling, the exhaust, the plumbing—is in service of that one decision you already made: which engine, and why. That decision is what this issue’s Engine Buyer’s Guide is built to support, and it lands in your hands at a moment when the choices facing builders have never been more varied or more consequential. 

The Engine Market in 2026 

Consider the landscape. Rotax’s 916 iS, now well into its service life, continues to prove itself in STOL and backcountry airframes, delivering 160 horsepower from 83 cubic inches on mogas—numbers that would have sounded fictional a generation ago. 

Edge Performance in Norway has pushed the Rotax platform further, with turbocharged Rotax‑based engines such as the EP917Ti rated at about 180 hp and equipped with a fully redundant dual‑ECU FADEC system.

Viking Aircraft Engines continues to expand its lineup of Honda and GM‑based conversions, with the turbocharged GM three‑cylinder “Viking 140T” now in flight testing and being promoted for use in Zenith and other experimental airframes.

MWfly’s liquid-cooled Italian engines now include a turbocharged line reaching 240 horsepower, with critical altitudes up to 20,000 feet. 

ADEPT’s V-6, for builders with deeper pockets and an early-adopter disposition, offers 425 horsepower from a package a foot narrower than a Continental 550. 

And the traditional Lycoming world remains very much alive—the IO-390 Thunderbolt, at 215 horsepower from a four-cylinder platform, continues to sell briskly, and Titan’s aftermarket alternatives give builders a path into the flat-engine ecosystem at lower cost. 

The Engine Buyer’s Guide is not intended to serve as a catalog. It is a departure point, a map of the territory you want to explore before committing your project’s future to a particular powerplant. Use it that way and use the manufacturers’ own data to verify what you find here. 

The Fuel Question

There is another dimension to engine selection this year that has not been part of the conversation before, at least not with this kind of urgency. In January, the FAA published its Draft Transition Plan to Unleaded Aviation Gasoline, laying out a phased framework to eliminate 100LL from the national fuel supply by the end of 2030. Three unleaded fuels—GAMI’s G100UL, Swift Fuels’ 100R, and LyondellBasell’s UL100E—are at various stages of approval. The plan does not mandate a single replacement, and many of the details remain to be worked out, but the direction is clear: leaded avgas is going away. 

For a builder choosing an engine today, this matters. Rotax engines already run on unleaded automotive fuel. Viking’s conversions were born on it. But if you are building around a traditional Lycoming or Continental, the question of what fuel your engine will burn five years from now requires more than a passing thought. The phase-out of 100LL is not really a cause for alarm—solutions are in the pipeline and the transition has been known for some time—but it is cause for awareness, and the Engine Buyer’s Guide is a good place to start factoring that variable into your planning. 

MOSAIC Comes to Full Flower

While we are on the subject of regulatory change, July 24, 2026, is the date when the aircraft-certification provisions of the MOSAIC rule take effect. The sport pilot privileges—expanded to include retractable gear, controllable-pitch propellers, and the new 59-knot stall-speed standard replacing the old weight limit—have been in force since last October. Now the manufacturing and certification side catches up with the new Part 22 framework for light-sport category aircraft. Lighter, more capable LSA designs entering the market under Part 22 will need engines that match their missions, and the ripple effects of that demand will show up in the Buyer’s Guide for years to come. Elsewhere in this Issue Jon Humberd continues his remarkable double build of a Zenith CH 750 Super Duty Xtreme and a modified CH 701—two very different airplanes from the same design lineage, both benefiting from the kind of builder ingenuity that makes Zenith’s all-metal approach so appealing to first-timers and veterans alike. His series is a clinic in practical decision-making, from engine selection to mission planning. Mike Davenport brings us a vintage aircraft rebuild of the Fairchild 24, one of the most graceful prewar designs to come out of American general aviation. It is a different kind of building story—restoration rather than assembly from a kit—but the skills and the patience required are every bit as demanding, and the result is an airplane that links the builder to a tradition stretching back to the 1930s. Our regular columnists are here as well. Andrew Robinson’s “Winging It,” Lisa Turner’s “Last Bits,” and Bill Wilson’s “Think Like a Builder” each bring their own angle to the craft of building and flying, and each is worth your time. 

The Season Ahead 

By the time you read this, Sun ‘n Fun will be in the rearview mirror—the forums, the fly-bys, the colorful aircraft. EAA AirVenture Oshkosh is now on the near horizon, July 20 through 26, and if you are planning to be there, the time to finalize those plans is now. 

EAA’s revised homebuilt judging criteria, which place renewed emphasis on builder logs and the amateur-builder ethos over pro-build polish, are worth studying if you intend to roll your airplane onto the flight line. But whether or not you are headed to Oshkosh, May and June are the months when homebuilding enthusiasm reaches full peak. The days are long, the hangar doors are open, and the work that may have seemed abstract in January is now hands-on. If the engine is the heart of the airplane, this is the season when you put heart and airframe together. The Engine Buyer’s Guide is a good starting point.