Flight Training - January/February 2023 - 15

HOW IT WORKS
BY THOMAS A. HORNE
FADEC
DIGITAL OVERWATCH FOR THE LATEST ENGINES
FROM DAY ONE OF OUR FLYING LIVES, PILOTS COME TO
intimately know an airplane's power controls. These controls-
throttle, propeller (in complex airplanes), and mixture-get a
workout every time you fly. When you move them to set power,
you're moving mechanical linkages that directly connect to levers,
gears, or other types of actuators on the carburetor or, in airplanes
with constant-speed propellers, mechanisms that allow engine oil
in and out of the propeller hub. You're in control.
That's all well and good, but what if you slam the throttle
forward too fast on takeoff? Or set the mixture so lean that
cylinder temperatures run too hot? Or set the mixture too rich
for your current power and altitude? Here's where full authority
digital engine control (FADEC) comes into play.
FADEC is a relatively recent type of digital engine control that
runs from inputs generated by a programmed electronic engine
controller. FADEC sensors sample a wide range of variables such
as air temperature, altitude, throttle position, engine temperatures
and pressures, engine and propeller rpms, fuel flow, electrical
system voltage, and a lot more. All this information is sent to the
FADEC's computers and electronic monitors, which have been
programmed to keep the engine from exceeding any temperature,
speed, or other limits-and also to provide optimum engine
performance. Even better, digital engine controls can also mean
pushbutton starting and single-lever power controls.
For safety's sake FADECs come with dual channels. If one
circuit malfunctions, the second channel is there for redundancy.
Running the pre-takeoff checklist, you'll check both
channels to make sure both are working, just as you check both
magnetos in a conventional-ignition engine.
Expect to see more FADEC systems installed in the future.
They're not just for turbine airplanes anymore. You may well
encounter them in complex piston singles as you step up to
newer, more capable airplanes. Bottom line: For all its complexity,
FADECs mean more efficient engine operations, precise
engine monitoring, longer service lives, better fuel efficiency,
and lower pilot workload.
tom.horne@aopa.org
Electro
Hydromechanial
Control Unit
Servo
Actuator
Position Solenoid
Sensor
Valves
ALT AIR
FADEC
Input from Aircraft
Power Supply
Commands/Inputs to
and from Engine
A greatly simplified schematic of a generic FADEC system shows that
the FADEC unit is king. It measures inputs to, and outputs from, the
engine. Its job is to deliver precise, optimal engine performance-without
exceeding any limitations (above). Although most often associated with
turbine engines, FADECs are making their way into high-performance
piston singles. The panel of a Tecnam P2010 Gran Lusso (right) shows
its guarded engine master switch (in red) and the FADEC selector toggle
switch (to its right). Auto is the normal switch position; the " force B "
switch position lets the pilot select a second, backup FADEC channel.
Pilot's Throttle
Display in Cockpit
ON
AUTO
E
E
PUSH
N
G
I
N
M
A
S
T
E
R
F
A
D
E
C
PUSH
HDG SYNC
FORCE B
H G
1-2
D
Mechanical Actuators
Position Sersors
FADEC
TEST
VOL ID
PUSH
NAV
ALT
FLIGHT TRAINING JANUARY/FEBRUARY 2023
15
STEVE KARP
Flight Training - January/February 2023

Table of Contents for the Digital Edition of Flight Training - January/February 2023
