The Pace of Innovation
Improvements in modern reciprocating engine production all start with the switch-over to more modern machining, which can cut metal to incredibly close tolerances. This means that a Continental, Lycoming or Rotax engine built today is a physically better aircraft engine than has ever been mass-produced. You might recall that Continental at one point offered a Platinum-series engine that cost more to buy but had tighter tolerances and therefore a longer warranty. With improvements in machining — including a change to automated manufacturing processes — all the engines Continental builds today meet or exceed the Platinum specifications, and so the special line has been discontinued.
Another significant difference between past aircraft engines and the current state of the art is the introduction of full-authority digital engine controls, or what’s referred to as fadec. Digital engine controls for production piston aircraft engines have been around for more than a decade, but they’ve undergone tremendous advances in that time. Continental’s and Lycoming’s latest integrated fadec technologies, for example, provide full electronic engine ignition, control of the engines’ sequential port fuel injection systems and engine management functions that monitor all parameters and digitally control fuel flow, with no pilot input needed.
Besides better engine optimization, this also means the pilot no longer needs to worry about leaning or enriching the engine fuel-air mixture as altitude increases or decreases. The computers do the work automatically, optimizing leaning in each cylinder, to attain maximum performance and efficiency in all conditions, including on takeoff from a high-density-altitude airport. Having a perfectly leaned engine all the time is a huge plus for efficiency and engine longevity.
“Our engines are truly single-lever control, with full thermal and propeller management,” noted Mike Craft, senior vice president and general manager for Lycoming. “It’s much closer to a modern turbine engine, where all the pilot has to worry about is what percent power is being generated. Everything else is controlled by the computers.”
Lycoming has applied its iE2 fadec technology in the TO-540 engine in the Lancair Evolution, as well as in the Northrop Grumman Firebird, an
“optionally piloted” spy plane (and one of Burt Rutan’s last designs at Scaled Composites).
Fadec systems in the latest piston aircraft engines electronically control the spark and fuel injection for optimal performance all the time. These engines still have manual mechanical throttles, but the onboard computers receive a steady stream of data related to parameters for manifold pressure, rpm, EGT and CHT, and then continuously adjust the mixture for peak performance. The fadec also automatically handles engine priming, starting and idle, and pushing just one button on the panel switches settings from best power to best economy.
The fuel delivery system in modern piston aircraft engines has also benefited from technological advancements. That Lycoming’s iE2 engine technology in the TO-540 engine employs a fuel injection system similar to the technology used in F1 shouldn’t come as a surprise: Lycoming developed the technology on the aircraft racing circuit with Jon Sharp in his Lycoming TIO-540-NXT-powered Nemesis Reno winner. That engine pioneered the Lycoming iE2 fadec technology, which controls fuel delivery with higher, constant pressure. “It allows you to do things that previously were not possible, such as how we manage fuel delivery to each cylinder,” Craft said.