Among the many reasons would-be owners have for not buying new airplanes, the one were most sick of hearing is the complaint about stale technology. You know it by heart:
For cryin out loud, those idiots in [fill in the aircraft manufacturing city of your choice] have been building the same old crap for 30 years, no wonder the industry is in the tank.
Sidestepping the chicken-and-egg argument about whether new ideas stimulate the market or whether demand spurs progress, one thing is certain: The new-age, electronically managed powerplant the NASA nerds have been flogging for years is actually close at hand. Indeed, you can probably buy one before the end of the year.
In past issues, weve reported on the full authority digital engine controls-FADECs-that the two major engine makers, Teledyne Continental and Lycoming are developing. Can you blame us for describing these things in the same wispy, over-the-horizon terms reserved for Mars missions? With the FAA involved in certification, weve expressed skepticism that piston-engine FADECs would come to pass in a reasonable time frame.
Yet barely two years after it was announced, Continentals FADEC appears to be within months of certification and delivery and is rapidly accumulating successful test hours in three and soon four aircraft. Lycoming lags slightly but expects to have its electronic system flying by late winter. A third company, General Aviation Modifications, Inc., is exploring yet another electronic ignition system. Its not yet flying but probably will before mid-year.
Hype and Hullabaloo
We expect when these systems hit the street, theyll be rolled out with all the fanfare and dawn-of-a-new-age hype associated with a Donald Trump grand opening. In truth, even if these systems work as claimed-and our guess is that they will-their significant achievement will be to have kicked the aircraft engine to the technological state of the average car motor circa mid-1990s. Warp drive they aint. At least for now.
Far be it from us to sneer at that, but in the short term, buyers of these systems may be well advised to calibrate their expectations downward. Electronic controls should deliver significant fuel savings-on the order of 10 to 15 percent-easier starting and single-lever, car-like engine operation, all of which are good things but just short of revolutionary.
If things work out as predicted, the largest benefit may lurk in the long term: Less maintenance, longer warranties and, combined with fuel savings, a reduction in operating costs, plus heretofore unseen diagnostic and operating data. That may sound like a moon shot, but it appears doable.
We first saw what has become the TCM FADEC system at Oshkosh in July of 1998. It was developed by a handful of engineers who left Hamilton-Standard to form a company called Aerotronics Controls, which later morphed into Aerosance after being bought by Teledyne Continental in 1997.
Far from a breadboard mock-up, the initial system had been proven on a non-aircraft engine and what we saw was close to production hardware on a Continental IO-240B. Certification was planned for spring of 1999 at a proposed cost in the $5000 to $8000 range. Aerosance missed the certification date by at least a year-so who hasnt?-but its cost estimates appear on target. During a visit to Continentals Mobile, Alabama plant in January, we were told that no certification showstoppers have arisen and it seems clear to us that TCM is aggressively pushing this system into the field.
From our visit, its obvious that the Aerosance FADEC is but one element in TCMs major and dramatic push to grow its business in what is still a relatively anemic engine market. TCMs Mobile plant has undergone a massive reorganization, virtually imploding inward with new investment in state-of-the-art machinery displacing older equipment with the intent of producing more engines and parts at costs and delivery times to compete with the aftermarket providers.
TCMs enthusiasm for FADEC is in keeping with a corporate culture that has traditionally tilted toward innovation, although not always successfully. Nor is the new TCM a one-trick pony, technologically. Also underway at a steady perk is research into an aircraft diesel engine which, if it delivers, could genuinely revolutionize piston engine powerplants. (Lycoming has a player in the same game, so both obviously see potential.)
Buyers of new cars dont give a second thought about how their ignition and fuel systems work. They merely turn the key and expect results. Aircraft owners are as similarly carefree, since these systems havent changed much in 50 years and, traditionally, if fed enough money, airplane ignition systems work reliably. And if not, well, insert more money.
Unlike the auto industry, aircraft makers have been spared the task of meeting ever-more-difficult emissions standards nor has fuel economy been a serious concern for owners who can afford an airplane in the first place. So why the push for engine electronics now? A combination of factors, the leading one being the perception that customers now expect this sort of enhancement. Fulfilling those expectations may be the only way an engine manufacturer can survive, let alone prosper.
There are significant if not dramatic economy gains to be made with FADECs but the longer term benefit may be longer engine life thanks to better temperature management. (If the engine makers back this up with longer warranties, the FADEC acolytes may be on to something.)
What It Does
The Teledyne/Aerosance system is at once simple and complex, with many parts and pieces but only one that moves: a tiny pintle valve in each fuel injector nozzle. Although it does a lot of electronic noodling, this system is easy to understand and, we predict, easy to maintain with the right tools, chiefly a laptop. In overview, the Aerosance system is similar to a modern automotive system, in that it relies on pulsed/timed fuel injection and variable spark timing to run the engine at peak efficiency for a given operational range.
This system replaces both mags with what are called master power controllers or MPCs, each of which provides spark for two cylinders. (A four-cylinder has two MPCs, a six-cylinder has three.) The MPCs are generally firewall mounted, although they can be placed elsewhere. Each MPC contains conventional induction coils with the make/break for high-voltage generation handled not by mechanical points but by the electronics, which reside in the base of each unit. Each MPC also controls fuel timing or pulse width through a massive wiring harness that runs power to each injector.
The injectors consist of a small hollow tube with a magnetic pintle seated against a sealing surface. A solenoid collar slips around the injector and provides the juice to open and close the pintle, metering fuel according to what the chips in the MPC calculate the engine actually needs. Similarly, ignition timing is adjusted to suit operational circumstance, be it full power climb or economy cruise.
Like automotive systems, this is a closed loop design, meaning that it has operating parameters written into the software and measures how well its hitting the desired numbers by sampling data from sensors on the engine, specifically cylinder head and exhaust gas temperatures. Unlike an automotive system, the FADECs grail is efficiency at consistent engine temperatures, not minimum emissions. So, where your car has a couple of oxygen sensors in the exhaust pipe, the FADEC doesnt. On the other hand, your cars engine computer doesnt care about cylinder temperatures, since the cooling system and thermostat tend to do that and liquid-cooled engines are relatively thermally stable.
Start Up, Take Off
At start-up, the FADEC immediately offers one benefit over conventional mags: A much more energetic spark than impulse couplings or shower of sparks can provide. If its a hot start, the FADEC does even better, since when powered down, the injectors close off the fuel flow and prevent the cylinders from becoming over rich. Theoretically, hot start problems should fade to a memory on a FADEC engine.
With magnetos, timing is fixed somewhere between 20 and 25 degrees before top dead center. Thats fine for cruise and lean conditions, but not good for starting, where zero advance is preferable. With these parameters programmed into its electronic brain, the FADEC has no trouble setting zero advance for starting (it actually retards a bit) and advancing as necessary during idling.
Unlike Unisons LASAR electronic mag, the Aerosance FADEC doesnt use mega ignition advance. Even under extreme lean conditions of economy cruise, timing peaks at 26 degrees BTDC, not the 41 degrees the LASAR mag could muster. (Six cylinders are limited to 22 degrees advance.) In fact, overreliance on timing was Continentals chief misgiving with the LASAR, an experience supported by users in the field.
We found that if the fuel/air ratios are right, advancing the timing beyond 22 degrees doesnt have much effect on economy, said John Barton, TCMs chief engineer. Of course, getting the fuel/air ratios right has proven no mean feat for both Continental and Lycoming.
The FADEC addresses this issue by managing each cylinders mixture discretely through sequential injection, as the automakers have done for years but which is new to aircraft engines. The system does this in one of two ways. During idle, climb or max cruise, it automatically sets each cylinders mixture to what amounts to a best-power lean condition; 75 to 125 degrees rich of peak EGT. (These specs are stored in a look-up table or fixed operating map.)
At power outputs below 75 percent, it reverts to what TCM calls hill climb mode and begins economy leaning to about 50 degrees lean of peak EGT. In the aircraft we flew, a Cessna 210 with a manual prop control, the hill climb transition occurred at settings below 2400 RPM. Presumably, a single-lever system will make the transition automatically based solely on the pilots power selection. The single-lever system will also require an electronic governor still in the works at Aerosance.
The FADEC therefore leans somewhat in virtually all operating regimes, unless rising CHTs dictate richer mixture for cooling. Mixture is controlled as in cars; via manipulating the injectors pulse width, longer for rich, shorter for lean. Again, CHTs rule. If they climb beyond limits-specifically 420 degrees F, variable with engine type-the cylinder gets more fuel for cooling. (If we had a choice, we would prefer a lower CHT limit, something below 400 degrees F.)
If we have any misgivings about this system, its the many sensors and wiring bundles it requires to operate. Theres a Hall effect sensor behind the cam gear to mark crank position, dual manifold pressure and temperature sensors, a fuel pressure sensor, and EGT and CHT sensors. Turbocharged engines will need TIT and knock sensors, although the latter isnt seen as necessary on normally-aspirated engines. And how about those electronic injectors? Will they be failure prone? Will sensors die like flies?
In truth, theres no rational reason to think so. This technology is well proven in the auto industry. If youve seen a check-engine light-probably an oxygen sensor-youve had a sensor failure. It happens. But mags fail and are probably more difficult to repair than this system will be. The basic maintenance philosophy is to replace failed components wholesale by diagnosing them with a laptop plugged into a data port. TCM ignition/fuel systems engineer Rick Quave showed us his analytical software for data acquisition and we thought it painted the system operation in surprisingly clear detail. A purpose-made, Windows-based diagnostic software package-which is planned-could very well make troubleshooting childs play. But to avoid such troubles in the first place, Quave explained that the FADEC will be one of the most mechanically robust new systems ever introduced into light aircraft GA. In jet engine FADECs, failures are often caused by plugs, connections and wiring so in the Aerosance FADEC, the harness is the single most expensive part of this system. Its festooned with milspec Cannon plugs and potted connectors, not the flimsy blade-and-socket junk found in the typical car and, unfortunately, on some airplanes. A splice kit will be available for field replacement of failed sensors.
Still, ignition failures are worrisome, and at the top of our list is a total electrical failure. To avoid that, the FADEC is wired to its own back-up battery and will automatically throw over from the aircraft bus if a failure occurs. Drawing 3 to 4 amps, the battery will run the system for about two to three hours. TCMs Barton told us some aircraft installations could be backed up with a second alternator rather than a battery, but initial certs will be dual battery.
Critical sensors are doubled up so if one tanks, the system will continue to function but will illuminate a warning light to alert the pilot to have the thing checked after landing. Each MPC has two chips, either of which can run the assigned cylinders through split channels. Losing one channel wont crump the cylinder but again, a warning light will annunciate the problem. If the engine-driven fuel pump fails, the system automatically turns on the boost pump and informs you that youre in limp-home mode. Similarly, if a CHT probe fails, the system reverts to a mapped leaning mode and illuminates a warning light.
Standard with each FADEC is something called an HSA or health status annunciator that samples system performance and shows fault lights for any problems it detects, including failed channels, components or power. An optional add-on is called the EPD or engine performance display, an instrument vaguely similar to a current-generation engine monitor but which provides a far more sophisticated means to glimpse the engine and system data the FADEC routinely collects. If this sounds like real-time engine operating diagnosis, thats what it is.
TCM test pilot Al Beech and engineer Quave gave us a brief demo in the companys IO-550-powered Cessna 210. The results were, frankly, underwhelming. And thats pretty much the idea, since the FADEC is supposed to simplify engine operation and transparently run with no burps. It does that, no question. The version we flew had two-levers: Throttle and prop, but no mixture.
Start-up is car like, other than the need to turn on the boost pump. All this does is charge the fuel lines until the engine-driven pump comes on line; since each cylinder gets the fuel it needs when it needs it, no priming, at least in the traditional sense, is necessary. For a hot start, same procedure. Forget high/low boost and coming up one hand short in manipulating throttle and mixture to coax a fuel-soaked hot engine to life.
Run-up is airplane like. Switching the mag switch merely runs the back-up circuits through their paces, illuminating lights on the warning panel to show that the channel-failure detection is working. As with mags, theres an RPM drop, since youre effectively dropping one channel-and one set of plugs-offline to check the systems diagnostics. In flight, operation is equally transparent. Push the throttle in to go fast, pull it back to slow down at any RPM youd like.
The 210 we flew wasnt equipped with fuel flow, so we couldnt sample the leaning performance. However, Quaves data computer showed that at RPMs below 2400, the system slowly-over a period of two minutes-backed the mixture to lean of peak, without the engine so much as rippling.
Our flight was hardly a serious wring out, of course. But the FADEC seems to work as claimed and its utterly seamless in operation. And therein lies a problem. As multi-thousand dollar improvements go, a FADEC is none-too-sexy. Its not a go-fast or look-snazzy improvement and your hangar neighbor wont sidle up and say, hey, nice FADEC… It probably will save fuel and give a slight power boost on takeoff. It may extend engine life and/or reduce maintenance costs. But will that be enough?
Predicting how well this system will do in the market is a crap shoot at this juncture. We simply have no sense of how owners will view the economics. Were convinced the early adopters will jump on this thing like white on rice. But Continental isnt wishing for a boutique, gear-head market; they want FADEC to become the new standard.
Consider some numbers. Assumptions: A six-cylinder FADEC installs for $7000, TBO is 1800 hours and gas costs an average of $2.15 a gallon. Lets assume a fuel savings of 12 percent, which is in the middle of the range the engineering data shows this system can deliver. If you fly 150 hours a year, that works out to roughly $600 in fuel savings.
Assuming the FADEC actually turns out to be set-and-forget, youll save some bucks on life cycle costs for the magnetos you no longer have. No more repetitive ADs, mid-TBO overhauls and replacements and the like. Whats that worth? Probably about $4000 to TBO, variable with engine type, not to mention the skin-off-the-knuckles factor. (Were giving the FADEC a bye here; if it requires more maintenance than mags, it may be doomed.)
Add up the fuel savings and magneto costs over the TBO run and the FADEC could conceivably save an owner $11,000 in gas and wrenching costs, if it delivers as promised. Not too shabby, especially for owners who fly lots. The numbers are less convincing for the 50-hour-a-year owner whose engine will time out rather than wear out. Ditto small displacement engines, which dont burn as much gas.
Moreover, if youre already a gear-head owner and youve tricked your engine out with GAMIjectors and run it aggressively lean of peak, the FADECs fuel savings wont be impressive if theyre even noticeable, although the maintenance savings might be. These economics may stymy all electronic systems, including those from Lycoming and GAMI.
What about the single-lever factor? In our view, this is purely eye-of-the-beholder stuff and our eye doesnt behold it. We think the concept has been oversold and we doubt that removing the prop/mixture will have any measurable impact on the marketability of light airplanes.
In truth, most airplanes with constant speed props have an RPM sweet spot that varies from day-to-day or with loading and other conditions. Moreover, if we want balls-to-the-wall RPMs for a short field takeoff, we would rather set that manually rather than leaving it up to the computer, thanks.
But were happy to leave mixture and timing control to a FADEC, so our preference is for a two-lever system, which has the additional benefit of eliminating an untried component, the electronic prop governor. (As TCM sees it, owners will have the option of manual RPM control.)
Were hearing some discussion that the FADEC may embolden engine makers and shops to extend warranties beyond the current somewhat stingy offerings, the theory being that the electronics will keep a ham-fisted pilot from trashing the engine. Thats good news if it comes to pass, but were skeptical that FADECs can pull that rabbit out of the hat. When 500 systems are out there in a couple of years, well see. Nice theory, but show us some results.
Is this technology a foregone conclusion? For some owners-those who fly large displacement engines often-our guess is yes, especially if the initial FADECs perform reliably. If they prove troublesome, with chronic and difficult-to-correct failures, owners will give them the same cold shoulder Unison experienced with the LASAR magneto. (Continental is hardly clueless about this and, in our view, has taken extraordinary steps to assure reliability.)
The airframers never embraced the LASAR magneto because they felt it didnt deliver any benefits. The same harsh test will be applied to FADECs. Cirrus is already chaffing to have the system and other manufacturers are reportedly paying attention. When Raytheon signs on to put FADEC into Bonanzas and Barons, this technology could be on its way.
Our prediction is that the FADEC market will develop steadily, if not dramatically, and within three years, owners will have a choice of electronic systems, not all of them full authority. Magnetos will be around forever, however, or at least until the day FADEC systems match them in price on small displacement engines. (We see that happening later rather than sooner.)
Last, we think Continental, Lycoming, GAMI and others deserve kudos for pursuing this technology aggressively. Despite glowing press releases and glad handing that the great GA turnaround is upon us, there are still far better ways to invest money than in anything related to light aircraft. This is risky development and it takes guts to do it.
FADECs may turn out to be but one factor that keeps the revival alive and were happy to see them coming.
Also With This Article
Click here to view the FADEC Checklist.
Click here to view the FADEC Revealed.
Click here to view “How FADEC Will Come to Market.”
Click here to view “GAMI’s Anti-FADEC.”
Click here to view “Why the Car Analogy Was, Is and Shall Ever Be Stupid.”
-by Paul Bertorelli
Contact- Continental at 334-438-3411 or www.tcmlink.com.