AOPA Pilot Editor in Chief Thomas B. Haines drives a Honda Pilot.
If you've ever attempted to hot-start a big-bore Continental or Lycoming engine, you may have asked yourself, "Why can't my airplane engine be more like my car engine?"
On a sweltering ramp faced by a curious crowd of onlookers you might have even thrown in a few additional words best not printed here. If the crowd holds up a scorecard of nine or 10, it probably means you've been flying that particular engine long enough to understand its nuances during a hot start. A little shot of the low fuel boost pump here, a flick of the vernier throttle there; hold your mouth just right; pray; and finally it catches, only to falter, stumble, and finally smooth out. If you run the battery down or overheat the starter, well, the scores will reflect that too.
Bryan Lewis, president and chief executive officer of Teledyne Continental Motors, admits he gets quizzed often by frustrated owners about why more automotive engine technology can't find its way into airplane engines. Or better yet, why not just put a car engine in your airplane? After all, we hear about that all the time in the kitplane world — or at least we used to.
After a couple of decades futzing with various car engines, most kitbuilders these days, who could put any rip-roaring engine they want into their steeds, are mostly installing plain-vanilla Lycoming and Continental engines.
In what appears to be a well-practiced response, Lewis patiently explains that aircraft engines are the way they are because they were purpose-built to be aircraft engines. Asking an engine built for your car to fill the powerplant role in your airplane would be unfair to both engine and airplane. "Aircraft engines look and act the way they do for specific reasons," says Lewis. "A car engine is designed for what it does. If you started over today and designed an aircraft engine, it would look pretty much the same as what we have now."
As Lewis points out, engines are designed for specific applications, whether it's for your car, tractor, race car, or airplane. Your car engine is optimized for roadway performance, with the ability to jackrabbit you out of a tough traffic situation and then loaf along at 55 or 65 mph using, oh, maybe 12 percent of its available power for hours on end. Use it that way and with minimal maintenance it will last for a decade and a couple hundred thousand miles. Meanwhile, the engine in your average race car quaffs copious amounts of exotic fuels while sprinting at high revolutions for a few hours at a time. It's good for maybe two races before it must be rebuilt.
Your aircraft engine, meanwhile, must first and foremost be light. Engine weight is important in modern automobiles striving for high fuel efficiency, but in aircraft engines it is paramount. That high-revving Mazda Wankel engine you think would be just the berries for your Mooney tips the scales at almost 350 pounds, not including oil, water, and a clutch. Add 150 pounds for the turbo system, plumbing, and the gear reduction you'll need to drop the engine's 5,000 rpm down to some level that your average propeller can absorb, and the thing appears downright portly compared to a Continental TSIO-360 on a Mooney 252, which checks in at less than 400 pounds.
That aircooled Continental engine will deliver 75-percent power for many, many hours at any altitude up into the lower flight levels where the temperature is well below zero. Ask the Mazda engine to perform at 75 percent continuously and you'll be very unhappy with the results, which is why you don't see such engines in widespread use in the kitplane market. And for those who have installed them, ask how many thousands of hours they get on the engine before it needs some serious work.
It's not like some bright engine minds haven't looked into this. You'll remember that a pair of Nissan engines powered the Pond Racer back in the early 1990s. These highly optimized 3-liter engines were designed to put out 1,000 horsepower, but never were turned up above about 600 horsepower. The twin-engine racer crashed during a qualifying round for the 1993 Reno Air Races, killing the pilot. But if a company like Nissan had seen a way to spin that technology into a mainstream aircraft engine, you would think we would be flying them by now. Likewise, Toyota certified a version of the Lexus automotive engine for aircraft use back in the early 1990s. The 360-horsepower V8 engine flew on various aircraft, but the company shelved the project.
Meanwhile, Honda has partnered with Continental not to bring an automotive engine to aviation, but to build — for research purposes, at least — a purpose-built aircraft engine.
Detroit calling
We don't need automotive engines in our airplanes; we need to adopt relevant automotive technologies to improve aircraft engines from a reliability, maintainability, and fuel-specifics standpoint. Several companies are attempting to do so, including Continental, which recently had its PowerLink FADEC (full authority digital engine control) system certified on the Liberty XL2. This is the first time that an airframe manufacturer has certified a FADEC on a production piston-powered airplane. PowerLink is being installed on several aircraft in the aftermarket. Lancair and Adam Aircraft are other airframers that are interested in adding the system to their products.
PowerLink is a true system in that it not only provides ignition, but also records data for later analysis (and someday for streaming to the maintenance shop while in flight) and provides alerts for potential maintenance issues. Dual computers replace the conventional magnetos, providing for variable spark timing, which allows the ignition and fuel flows to be optimized for starting — whether hot or cold. FADEC's single lever manages the throttle, mixture, and ultimately the prop control to deliver fuel savings of about 15 percent over a conventional ignition system. Some purists will argue that they like to futz with the three knobs (six in your twin), but there's no doubt that a well-tuned FADEC can better manage the engine throughout the flight envelope than even a pilot skilled in powerplant control. And certainly during high-workload phases of flight, such as takeoff and landing, FADEC can be of real assistance.
Most interesting, especially for those of us flying high-horsepower and turbocharged engines, Lewis says that PowerLink-equipped engines can fly on high-octane automotive fuels, providing a solution to the supposed phasing out of leaded avgas. Most alternative fuels solutions floated heretofore have left high-compression engines and especially turbocharged engines with no good alternatives.
PowerLink is already certified for use on a number of engines — both Continental and Lycoming. Look for even more approvals soon.
Not so new
While FADEC is receiving a great deal of discussion in the piston-engine market, it is not new. Jets have been employing similar technology, also called FADEC, for a number of years. FADEC and its cousin DEEC (digital electronic engine computer) help busy turbine pilots manage their engines. With the electronic controls, pilots no longer need to calculate complex takeoff power settings. The electronics take into account the temperature and altitude. The pilot simply advances the thrust levers to the stops for takeoff. FADEC or DEEC keeps the engines from hurting themselves. Right after takeoff, slide the levers back to the maximum continuous power setting for climb. Upon leveling off, the pilot may slide the levers back one more notch for cruise.
Owners of expensive turbine engines learned long ago that pilots are better at managing systems than they are at finessing power controls. The result has been much better reliability and longer life for turbine engines. In fact, with the help of electronics, reliability has become so predictable that most operators pay a flat fee per hour for maintenance and many turbine engines are moving away from overhaul cycles to "on condition" replacement or overhaul of various parts. In other words, the part gets replaced when it needs to be replaced, not according to some unilateral schedule.
We're not there yet with piston engines, but there is great promise that our decades-old engine designs purpose-built for airplanes can carry us well into the twenty-first century — with a little help from some electrons.
E-mail the author at [email protected].
Links to additional information about new aircraft engine technology may be found on AOPA Online ( www.aopa.org/pilot/links.shtml).
