An almost universal lament among pilots is that we are flying piston engines that use decades old technology. That’s not entirely true, but you would be hard pressed to find a magneto on any other type of piston engine still in production.
Continental spent a ton of dough to change that situation starting in the late 1990s and its efforts were shot down. Not by the stuck in the mud regulators at the FAA, but by pilots. The very people who say they want technology advances.
The really big improvements in other piston engines such as those in cars and trucks have come from computer control of the entire engine operation. Automated and constantly adjusting control of ignition and fuel have made automotive engines more efficient, more responsive, easier to start, more drivable and more durable. Why can’t we have that in our piston airplanes?
In aviation we call computerized control of an engine full-authority digital engine computer (FADEC). The term came from the turbine engine world where redundant computers were handed the job of controlling fuel flow and other operating parameters to set power, and more importantly, always keep the jet engine within operating limits. I can’t think of a jet in production that doesn’t have FADEC engines.
Before FADEC pilots of jets would be charging down the runway gently moving the throttles to try to find a target fan rpm (N1) or engine pressure ration (EPR). Move the levers too much and you could overspeed and damage the engine. If you don’t move the levers far enough the engines don’t put out the expected power and takeoff performance suffers. Just when a pilot should be monitoring directional control and critical systems during takeoff roll in the pre-FADEC days we had our eyes glued to a couple gauges while we doinked around with the power levers.
Operating most piston engines doesn’t demand quite as much attention, but mismanagement of the controls can damage the engine, or result in less power than expected. FADEC can simplify piston engine operation to nothing more than moving a lever just like stepping on a gas pedal. FADEC would automatically optimize the mixture for all atmospheric and operating conditions to gain maximum engine performance and efficiency while also protecting the engine from the pilot who can use the engine controls in a damaging way.
A big hurdle on the way to piston FADEC was an uninterruptible electrical power source. The traditional piston engine with its magnetos and carburetor or mechanical fuel injection operates with total independence from the aircraft electrical system. And that’s good. Many piston airplanes have very rudimentary electrical systems, and more importantly, have only one of them.
At first it looked like only airplanes with totally redundant transport aircraft type electrical systems could use FADEC. To install the Porsche PFM engine Mooney created such an electrical system. The electrics worked OK, but the engine didn’t pan out.
But Continental was successful in convincing the FAA that a FADEC backup battery could do the job. FADEC doesn’t use that much power so it’s not hard to have a constantly charged dedicated battery with enough power to equal the fuel endurance of the airplane. If the main electrical system failed totally the backup battery would keep FADEC and the engine running until the fuel was gone.
There were several fits and starts on the way to FADEC certification. But Continental succeeded, first in naturally aspirated engines, and then for the turbos. I flew several iterations of the system and the final go worked very well. Just push the throttle and let the computer manage the engine. I even had the magnetic pickups installed on an accessory gear in my new engines in 2000 in the certainty that I would be converting to FADEC before long.
But Continental needed an airplane manufacturer to really launch FADEC. A logical target was Beech with the Continental powered Bonanza and Baron. Beech engineers loved the idea. Beech customers hated it. When Beech asked prospects they learned that not only didn’t sales prospects want FADEC, many wouldn’t buy an airplane with the system.
The problem was mixture control. Many, even most pilots, thought they were smarter than the FADEC computer. They wanted to run lean of peak or rich of peak, or somehow set the mixture to suit their conviction of how it should be done. FADEC, on the other hand, would run lean of peak under some power settings and conditions, but then switch rich of peak for other conditions. And it did this without considering pilot opinion, only what testing showed was optimum for the engine.
So FADEC, fully developed and certified, faded away. Pilots who demand new technology, it turns out, don’t really want it if it interferes with lore, superstition, and years of experience.
It’s interesting that this is not an issue in some newer design engines such as the Rotax that doesn’t have decades of operating lore behind it. And if new diesels are successful they will all be FADEC so the pilot never had the chance to diddle with engine controls and won’t miss it.
But for the big majority of piston engines I now expect to die, or at least hang up my flying shoes, with mechanical fuel injection, magnetos and that supremely important mixture control still flying in most piston airplanes. My guess is that piston engine mixture and rpm operating techniques have passed into the realm of pilot religion, and all religions resist the new no matter what science may show. Just ask Copernicus.