The aircraft magneto is a cursed thing.
Its technology seemingly dates to the discovery of fire, every engine needs at leasttwo and on a dark and stormy night over the Appalachians, the last thing you want to thinkabout is how many fragile moving parts are whirling around inside a mag at the speed ofheat.
But just try to come up with something better. Or even something that’s almost as goodthat doesn’t cost three times as much. That’s precisely the challenge the engine andairframe industry faces as it marches smartly up to the toll gates on Al Gore’s bridge tothe 21st century.
Some segments of the industry are positively euphoric with talk about electroniccontrols that will re-invent the way pilots operate engines, with improved fuel economy,easier starting and-gasp-better longevity. We’re seeing the word "revolutionary"appearing in every other line of more than a press release or two.
While there’s a certain inevitability to electronics in the engine compartment, it’salso true that bringing these things successfully to market has thus far been a snake-bitproposition. The problem is not making systems that work or certifying them, butconvincing buyers that the benefits of electronic controls are worth the asking price andgenerating enough sales volume to keep bean counters from pulling the plug.
As of summer 1998, the push for FADECs-full-authority digital engine controls-screechedto fever pitch, with both Lycoming and Continental developing clean-sheet electroniccontrol systems and a couple of other companies proposing FADECs or related systems oftheir own.
We have to give these guys a tip of the hat for persistence. Over the last decade,electronic engine controls haven’t exactly sparked a buyer stampede. Much as we hate todredge up ancient history, the ill-fated Porsche Mooney PFM comes first to mind.
Introduced in 1988, the PFM was a giant boulder tossed into the ripple-free,technological calm of GA. And it sank just about as fast. The PFM was powered by asix-cylinder, air-cooled engine with automotive-style electronic ignition, fuel injection,autoleaning, automatic cooling control and-what was supposed to be the irresistiblemarketing lure-a single power lever.
It worked; push the throttle forward to go fast, pull it back to slow down. No prop, nomixture and no worries about shock cooling. Even though it was a bit slower than the 201,owners loved the airplane. Unfortunately, there weren’t many of them. Only 41 PFMs weresold, a poor sales history due in part to the $60,000 price premium over the 201 and aflat GA market. Thanks to slow sales and money squabbles with Mooney, Porsche grewdisenchanted and bailed out of the project. To its credit, it has continued to support theengine.
More recently, another European company, Rotax, developed an 81 HP engine used in thepopular Diamond Katana trainer. Again, electronic ignition, autoleaning and worry-freecooling thanks to partial watercooling. Although it has no mixture knob, the Rotax has aconventional prop control and throttle.
This progressive powerplant was well received and despite glitches with the electronicsand maintenance difficulties due to lack of familiarity with the systems, owners like theRotax/Katana combination. Yet once again, the engine manufacturer became disinterested inpromoting its engine in the aviation market, leaving Diamond to fend for itself. Diamondhas since abandoned Rotax in favor of Continental’s IO-240B, a fuel-injected conventionalaircraft engine with none of this new-age digital gimcrackery that allows any fool tostart a heat-soaked motor.
More recently yet is Unison’s LASAR ignition system, the world’s first limitedauthority electronic magneto, with bulletproof conventional reversion and automaticvariable timing. LASAR drew intense interest when it appeared at Oshkosh three years agobut the system’s performance gains have proved elusive and sales anemic. With nodiscernible benefit to offset the added cost of installing it, the airframe makers havethus far passed on LASAR.
Against this backdrop, how do the developers of the next generation of electroniccontrols hope to succeed? What will they do differently?
It’s the Money, Stupid
Setting aside the technobabble for a moment, one immediate distinction over previoussystems is that the two major players here-Continental and Lycoming-intend to offer theirFADECs on new engines to be installed in new airplanes at a cost comparable to current newengines.
That means that a new Cessna 182 costing $225,000 with the current iteration of theLycoming IO-540 would cost about the same with a new FADEC-driven engine.
"If we have learned anything about the GA market," says Lycoming’s headengineer, Rick Moffett, "it’s that it’s extremely price sensitive. People just aren’tgoing to spend $20,000 for an engine control system." Anyone who doubts that merelyneeds to recall Mooney’s PFM experience.
Second-and ignoring the retrofit market-these systems will capitalize on theflexibility and capability of state-of-the-art digital electronics to produce anintegrated system that includes sexy cockpit displays and, no doubt, onboard diagnosticsof some kind.
Even at that, Moffett says meeting the price point will be a tall order. Ridding acurrent engine of its conventional mags and harnesses, injector servo, flow dividers,waste gates plus such cockpit instrumentation as manifold pressure, tachs and enginegauges will have to save enough money to pay for -or at least almost pay for-thenew electronics.
"If we hit it within five percent, we’ll consider ourselves successful," saysMoffett. Add up the cost of all that conventional hardware and you you’ll arrive at someidea of what a retrofit FADEC for an older airplane would cost: Our guess is between $6000and $10,000.
The rest is pure sales. Fuel economy gains of 10 to 15 percent seem likely; engineswith electronic ignition are demonstrably easier to start and, in theory, without thepilot whipsawing the power or trashing the valves by mis-leaning, an engine might actuallystand a better chance of reaching TBO. The single-power lever concept may or may not be amarket draw. Frankly, we doubt that it is.
At Oshkosh, both Lycoming and Continental announced FADEC systems and a third company,Aurora Flight Sciences is already flying a single-lever system developed under a NASAsmall business technology grant. We suspect the two major players will producemarket-ready systems within a year or two.
Lycoming has joined with Unison to develop the so-called EPiC FADEC, for electronicpropulsion integrated control. Continental will likely use a system being developed byAerosance, Inc., (formerly Aerotronics) a Connecticut company bought earlier this year byTCM’s parent, Allegheny Teledyne, specifically to engineer electronic controls for pistonengines. But the Aerosance-TCM marriage isn’t meant to be monogamous; Aerosance is free tosell its technology to all comers, presumably including Lycoming. Both systems willincorporate the single-power lever concept to one degree or another, although at thispoint, it appears as though Aerosance is more committed to a fully automated enginecontrol which entirely eliminates pilot input, save for a single power control lever.
We recently toured Aerosance’s research and production facility in Farmington,Connecticut and were shown a Continental IO-240B running on a prototype FADEC. By currentstandards, the Aerosance system is a radical departure and although it shares commonground with the Porsche Mooney engine in principle, it will also pioneer some intriguingnew components.
Gone, of course, are traditional engine-driven magnetos, replaced by a high-energyspark coil for each cylinder. Variable timing will be controlled by a microprocessor foreach cylinder. Fuel will be direct port injection through a new electronic pulsed injectorAerosance has developed to replace the continuous flow injectors that are standardequipment in aircraft engines.
Aerosance’s design is a closed loop system, meaning that it uses a series ofsensors-manifold pressure, fuel pressure, cylinder head and exhaust gas temps, enginespeed, knock detection, turbo boost pressure-to operate the engine to a set of fixedcontrol laws burned into the FADEC’s brain. Virtually all of the hardware for this systemis clean-sheet stuff, including the coils, electronics, a master speed sensor that willoccupy one of the magneto pads, electronic monitoring and annunciation. Still underdevelopment are an electronic prop governor and a waste-gate controller for turbochargedengines.
Like the Porsche Mooney system, the Aerosance FADEC is all-electric, with no mechanicalreversion. For redundancy, each microprocessor controls two cylinders and each coilgenerates spark for two cylinders. Aerosance envisions dual electrical power sources, withback-up provided by an optional engine-driven, self-exciting generator, another componentunder development.
Being fully automatic, the Aerosance system relies on the FADEC’s fixed operatingparameters, with the only pilot controlled variable being throttle position. We were toldthat these parameters are still being tweaked but basically, each microprocessor wouldcontrol the combustion in each cylinder as an independent event, with timing and fuel flowelectronically manipulated to deliver either best power or best economy.
The optimum operating mode would be based on throttle position and power outputcalculated not by direct measurement but surmised from a "look-up" tabledeveloped from the dyno-derived power charts.
Like the LASAR system, the Aerosance FADEC would probably apply very little sparkadvance for takeoff power but would advance timing and lean aggressively in cruise. Wouldthat include lean-of-peak EGT operation? Probably, says Aerosance CEO Steve Smith.
Standard equipment with the Aerosance system will be something called a health statusannunciator, a small panel-mounted box that watches over each cylinder and combines CHT,oil pressure and other sensors and signals out-of-limit conditions.
An optional accessory is the Engine Performance Data Display, which is a graphicmonitor device that displays power level, fuel level and consumption, EGTs, oil temps andother useful engine info. The EPDD could store engine operating history from zero-time toTBO.
Easing Into It
Compared to the Aerosance system, the Lycoming-Unison EPiC represents a moreconservative approach to FADEC. On injected engines, it would do away with the Bendix/RSAservo system but would retain a simpler throttle body assembly and conventional constantflow injectors.
As currently being tested on an IO-540, EPiC uses the next generation of LASAR magswith electronic spark advance controlled by a single-channel FADEC computer. Reversion ispurely mechanical, with an engine-driven fuel pump and the LASAR’s conventional magnetoback-up mode. Current versions of the LASAR system advance timing based on fixed look-uptables burned into the system’s chips, using manifold pressure, RPM and CHT input.
EPiC will do the same, by reference to a fixed look-up table, with power outputindirectly calculated from sensor input. Lycoming’s Moffett told us that these powertables are being revisited during FADEC trials and lean-of-peak EGT operation will beconsidered. Like Aerosance , EPiC will have a cockpit display; details on that haven’tbeen settled yet.
Interestingly, EPiC may not be a strict single-lever system that would limit pilotinput to throttle position only. Moffett and Unison’s Norman MacLeod told us the systemmay very well have a pilot-selectable switch for best power versus best economy.Presumably, switching to best economy would engage a more aggressive leaning map. Lycomingis currently polling the airframe makers about this option. (We think it’s a good idea inthat some efficiency is reclaimed in not surrendering engine operation to aone-size-fits-all-dumb-as-rock mode.
What’ll They Do?
What are FADEC’s claimed benefits? Easier starting and improved fuel economy, to nametwo. We think these have been convincingly proven by the LASAR system, even if economygains have been minuscule in the field. There’s no doubt that if they work as claimed,single-lever power controls will simplify pilot workload. Whether that will yield muchmarket stimulation is an open question, however. We shopped the idea to Michael Slingluff,CEO of Diamond, whose IO-240-powered Katana may be the first production airplane to usethe Aerosance system.
"There’s no weight savings and no cost savings. If these systems take out some ofthe operational variability and you get an upgraded warranty, then yes, it has marketappeal," says Slingluff, adding that sooner or later, electronic engine controls willbe an expectation, especially in high performance airplanes. He believes sophisticatedcockpit displays are essential to add curb appeal and salability to FADECs.
Besides simplicity of operation, a FADEC’s chief claimed benefit is improved thermalmanagement of the engine, reducing shock cooling, spikey CHTs and other temperatureexcursions thought to be bad for engine longevity. In other words, greater likelihood ofreaching TBO. Lycoming’s Moffett says maybe, but he’s fearful of overpromising a benefitthat may take years to materialize, if it ever does.
From what we’ve seen thus far, both Aerosance and Lycoming-Unison are on the righttrack and we’re excited about the prospects. That said, we would still like to see morefundamental research into improved induction and exhaust systems-that appears to behappening at Lycoming-and development of control laws based on direct measurement of poweroutput, rather than the necessarily compromised fixed power tables.
Still, the rather large nut to crack is to produce FADECs that are as reliable as thevenerable magneto at a competitive cost. We suspect that all of the players in this gamewill find that far more difficult than pesky problems with computers and circuit boards.