MD-11 Flight Crew Operations Manual
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Engines -
Description and Operation
Eng.10.2
• Thrust control as a function of throttle position and thrust reverser lever.
• Protection from exceeding N1, N2, internal pressures, and maximum
thrust limits.
FADEC is controlled by an Engine Control Unit (ECU).
Looking aft, the ECU is mounted on the engine fan case at the four o’clock
position.
The two channels (A and B) of the ECU are housed in one assembly but are
physically separated.
The ECU has dual channel control (A and B). This allows normal engine control
and operation with the total failure of one channel. The failure of any sensor
results in cross-channel data exchange so that dual-channel capability is retained.
Primary power for each channel is obtained from a dual-output Permanent Magnet
Alternator (PMA) driven by the N2 gearbox. The PMA has two independent sets
of windings. Each set of windings supplies power to its respective ECU channel.
Aircraft 28-volt input power is required for ground starting, testing and ECU
back-up power. Back-up power (28 VDC aircraft power) to the ECU is standard
and available five minutes after the engine is shutdown.
The ECU is the primary interface between the aircraft and the engines. The ECU
operates in response to pilot commanded thrust settings that are transmitted to the
ECU by dual electrically isolated position sensors. The position sensors are
mechanically linked to each throttle. Each position sensor is dedicated to one
channel of the ECU and provides independent analog signals to each ECU channel
proportional to the throttle angle.
The ECU interfaces with two Air Data Computers (ADC) through two ARINC
429 data buses. Each ECU channel receives parameters from both ADCs. These
parameters include:
• Pressure altitude.
• Total pressure.
• Total air temperature.
FADEC MODE switches on the forward overhead panel allow the flight crew to
select the alternate control mode of the ECU. Selection of the alternate mode is
required when a primary air data parameter is not available to the ECU. The
alternate mode can also be selected by pushing the throttles past the normal
forward stop. This provides up to 5% N1 (approximately 10% thrust) increase
depending on SAT.
Reverting to the alternate mode will never result in a decrease in thrust, but may
result in an increase in thrust and exceedance of limits.
October 02, 2006
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