Why are our piston aircraft still flying around with 40-year-old tractor mags and a fistful of engine controls, instead of modern digital single-lever systems? A decade ago, Mooney tried to change this with the Porche-powered PFM, but sold only 41 of the airplanes. Three years ago, Unison introduced the Slick LASAR, but it too went over like a lead balloon. Now, both TCM and Lycoming are readying their own digital engine control systems slated to appear in a year or two. Here's an update on TCM's Aerosance and Lycoming/Unison's EPiC from the staff of Aviation Consumer.
December 20, 1998
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The aircraft magneto is a cursed thing.
Its technology seemingly dates to the discovery of fire, every engine needs at least
two and on a dark and stormy night over the Appalachians, the last thing you want to think
about is how many fragile moving parts are whirling around inside a mag at the speed of
But just try to come up with something better. Or even something that's almost as good
that doesn't cost three times as much. That's precisely the challenge the engine and
airframe industry faces as it marches smartly up to the toll gates on Al Gore's bridge to
the 21st century.
Some segments of the industry are positively euphoric with talk about electronic
controls 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's
also true that bringing these things successfully to market has thus far been a snake-bit
proposition. The problem is not making systems that work or certifying them, but
convincing buyers that the benefits of electronic controls are worth the asking price and
generating enough sales volume to keep bean counters from pulling the plug.
As of summer 1998, the push for FADECs-full-authority digital engine controls-screeched
to fever pitch, with both Lycoming and Continental developing clean-sheet electronic
control systems and a couple of other companies proposing FADECs or related systems of
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 to
dredge 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 a
six-cylinder, air-cooled engine with automotive-style electronic ignition, fuel injection,
autoleaning, automatic cooling control and-what was supposed to be the irresistible
marketing lure-a single power lever.
It worked; push the throttle forward to go fast, pull it back to slow down. No prop, no
mixture 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 were
sold, a poor sales history due in part to the $60,000 price premium over the 201 and a
flat GA market. Thanks to slow sales and money squabbles with Mooney, Porsche grew
disenchanted and bailed out of the project. To its credit, it has continued to support the
More recently, another European company, Rotax, developed an 81 HP engine used in the
popular Diamond Katana trainer. Again, electronic ignition, autoleaning and worry-free
cooling thanks to partial watercooling. Although it has no mixture knob, the Rotax has a
conventional prop control and throttle.
This progressive powerplant was well received and despite glitches with the electronics
and maintenance difficulties due to lack of familiarity with the systems, owners like the
Rotax/Katana combination. Yet once again, the engine manufacturer became disinterested in
promoting its engine in the aviation market, leaving Diamond to fend for itself. Diamond
has since abandoned Rotax in favor of Continental's IO-240B, a fuel-injected conventional
aircraft engine with none of this new-age digital gimcrackery that allows any fool to
start a heat-soaked motor.
More recently yet is Unison's LASAR ignition system, the world's first limited
authority electronic magneto, with bulletproof conventional reversion and automatic
variable timing. LASAR drew intense interest when it appeared at Oshkosh three years ago
but the system's performance gains have proved elusive and sales anemic. With no
discernible benefit to offset the added cost of installing it, the airframe makers have
thus far passed on LASAR.
Against this backdrop, how do the developers of the next generation of electronic
controls hope to succeed? What will they do differently?
It's the Money, Stupid
Setting aside the technobabble for a moment, one immediate distinction over previous
systems is that the two major players here-Continental and Lycoming-intend to offer their
FADECs on new engines to be installed in new airplanes at a cost comparable to current new
That means that a new Cessna 182 costing $225,000 with the current iteration of the
Lycoming 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 head
engineer, Rick Moffett, "it's that it's extremely price sensitive. People just aren't
going to spend $20,000 for an engine control system." Anyone who doubts that merely
needs to recall Mooney's PFM experience.
Second-and ignoring the retrofit market-these systems will capitalize on the
flexibility and capability of state-of-the-art digital electronics to produce an
integrated system that includes sexy cockpit displays and, no doubt, onboard diagnostics
of some kind.
Even at that, Moffett says meeting the price point will be a tall order. Ridding a
current engine of its conventional mags and harnesses, injector servo, flow dividers,
waste gates plus such cockpit instrumentation as manifold pressure, tachs and engine
gauges will have to save enough money to pay for -or at least almost pay for-the
"If we hit it within five percent, we'll consider ourselves successful," says
Moffett. Add up the cost of all that conventional hardware and you you'll arrive at some
idea of what a retrofit FADEC for an older airplane would cost: Our guess is between $6000
The rest is pure sales. Fuel economy gains of 10 to 15 percent seem likely; engines
with electronic ignition are demonstrably easier to start and, in theory, without the
pilot whipsawing the power or trashing the valves by mis-leaning, an engine might actually
stand a better chance of reaching TBO. The single-power lever concept may or may not be a
market 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 NASA
small business technology grant. We suspect the two major players will produce
market-ready systems within a year or two.
Lycoming has joined with Unison to develop the so-called EPiC FADEC, for electronic
propulsion integrated control. Continental will likely use a system being developed by
Aerosance, Inc., (formerly Aerotronics) a Connecticut company bought earlier this year by
TCM's parent, Allegheny Teledyne, specifically to engineer electronic controls for piston
engines. But the Aerosance-TCM marriage isn't meant to be monogamous; Aerosance is free to
sell its technology to all comers, presumably including Lycoming. Both systems will
incorporate the single-power lever concept to one degree or another, although at this
point, it appears as though Aerosance is more committed to a fully automated engine
control 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 current
standards, the Aerosance system is a radical departure and although it shares common
ground with the Porsche Mooney engine in principle, it will also pioneer some intriguing
Gone, of course, are traditional engine-driven magnetos, replaced by a high-energy
spark coil for each cylinder. Variable timing will be controlled by a microprocessor for
each cylinder. Fuel will be direct port injection through a new electronic pulsed injector
Aerosance has developed to replace the continuous flow injectors that are standard
equipment in aircraft engines.
Aerosance's design is a closed loop system, meaning that it uses a series of
sensors-manifold pressure, fuel pressure, cylinder head and exhaust gas temps, engine
speed, knock detection, turbo boost pressure-to operate the engine to a set of fixed
control laws burned into the FADEC's brain. Virtually all of the hardware for this system
is clean-sheet stuff, including the coils, electronics, a master speed sensor that will
occupy one of the magneto pads, electronic monitoring and annunciation. Still under
development are an electronic prop governor and a waste-gate controller for turbocharged
Like the Porsche Mooney system, the Aerosance FADEC is all-electric, with no mechanical
reversion. For redundancy, each microprocessor controls two cylinders and each coil
generates spark for two cylinders. Aerosance envisions dual electrical power sources, with
back-up provided by an optional engine-driven, self-exciting generator, another component
Being fully automatic, the Aerosance system relies on the FADEC's fixed operating
parameters, with the only pilot controlled variable being throttle position. We were told
that these parameters are still being tweaked but basically, each microprocessor would
control the combustion in each cylinder as an independent event, with timing and fuel flow
electronically manipulated to deliver either best power or best economy.
The optimum operating mode would be based on throttle position and power output
calculated not by direct measurement but surmised from a "look-up" table
developed from the dyno-derived power charts.
Like the LASAR system, the Aerosance FADEC would probably apply very little spark
advance for takeoff power but would advance timing and lean aggressively in cruise. Would
that include lean-of-peak EGT operation? Probably, says Aerosance CEO Steve Smith.
Standard equipment with the Aerosance system will be something called a health status
annunciator, 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 graphic
monitor device that displays power level, fuel level and consumption, EGTs, oil temps and
other useful engine info. The EPDD could store engine operating history from zero-time to
Easing Into It
Compared to the Aerosance system, the Lycoming-Unison EPiC represents a more
conservative approach to FADEC. On injected engines, it would do away with the Bendix/RSA
servo system but would retain a simpler throttle body assembly and conventional constant
As currently being tested on an IO-540, EPiC uses the next generation of LASAR mags
with electronic spark advance controlled by a single-channel FADEC computer. Reversion is
purely mechanical, with an engine-driven fuel pump and the LASAR's conventional magneto
back-up mode. Current versions of the LASAR system advance timing based on fixed look-up
tables 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 output
indirectly calculated from sensor input. Lycoming's Moffett told us that these power
tables are being revisited during FADEC trials and lean-of-peak EGT operation will be
considered. Like Aerosance , EPiC will have a cockpit display; details on that haven't
been settled yet.
Interestingly, EPiC may not be a strict single-lever system that would limit pilot
input to throttle position only. Moffett and Unison's Norman MacLeod told us the system
may 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. Lycoming
is currently polling the airframe makers about this option. (We think it's a good idea in
that some efficiency is reclaimed in not surrendering engine operation to a
What'll They Do?
What are FADEC's claimed benefits? Easier starting and improved fuel economy, to name
two. We think these have been convincingly proven by the LASAR system, even if economy
gains 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 much
market 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 use
the Aerosance system.
"There's no weight savings and no cost savings. If these systems take out some of
the operational variability and you get an upgraded warranty, then yes, it has market
appeal," says Slingluff, adding that sooner or later, electronic engine controls will
be an expectation, especially in high performance airplanes. He believes sophisticated
cockpit displays are essential to add curb appeal and salability to FADECs.
Besides simplicity of operation, a FADEC's chief claimed benefit is improved thermal
management of the engine, reducing shock cooling, spikey CHTs and other temperature
excursions thought to be bad for engine longevity. In other words, greater likelihood of
reaching TBO. Lycoming's Moffett says maybe, but he's fearful of overpromising a benefit
that may take years to materialize, if it ever does.
From what we've seen thus far, both Aerosance and Lycoming-Unison are on the right
track and we're excited about the prospects. That said, we would still like to see more
fundamental research into improved induction and exhaust systems-that appears to be
happening at Lycoming-and development of control laws based on direct measurement of power
output, rather than the necessarily compromised fixed power tables.
Still, the rather large nut to crack is to produce FADECs that are as reliable as the
venerable magneto at a competitive cost. We suspect that all of the players in this game
will find that far more difficult than pesky problems with computers and circuit boards.