SECTION 5
ELECTRONIC ENGINE CONTROL
© IAE International Aero Engines AG 2000
IAE V2500 Line and Base Maintenance Electronic Engine Control
Electronic Engine Control Introduction
The V2500 uses a Full Authority Digital Electronic Engine • Six ‘screened’ pressure ports provide the required
Control (FADEC). pressure inputs to both channels.
The FADEC comprises the sensors and data input, the • Built in handle facilitates removal and handling.
electronic engine control unit (EEC) and the output
devices, which include solenoids, fuel servo operated • Has three control modes in each channel. Engine
actuators and pneumatic servo operated devices. The Pressure Ratio (EPR) – which is the Primary thrust
FADEC also includes electrical harnesses. control Mode. N1 Rated and Un-rated and also
provides Auto Starting and Thrust Reverser control. (To
Engine Electronic Control be covered in detail later).
The heart of the FADEC is the Engine Electronic Control • Schedules engine operation to provide maximum
(EEC) unit - shown below. The EEC is a fan case mounted engine performance and fuel savings.
unit, which is shielded and grounded as protection against
EMI - mainly lightning strikes. • Provides improved engine starting (Auto Start) and
transient characteristics (acceleration/deceleration).
Features
• Provides maximum engine protection and is more
• Vibration isolation mountings. flexible to readily adapt to changes in engine
• Shielded and grounded (lightning strike protection). requirements.
• Size - 15.9 X 20.1 X 4.4 inches.
• Weight - 41 lbs.
• Two independent electronic channels.
• Two independent power supplies, the EEC utilises
67.53 Watts of power from either the three phase AC
from a dedicated engine mounted alternator, or 28
Volts DC from an aircraft source.
• A two way Pressure Relief Valve maintains the units
differential pressure (< 5 PSID).
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The Engine Electronic Control (EEC) Description
The EEC is a dual channel control unit that utilises a split
housing design containing two multi-layer printed circuit
board assemblies, which enables it to function as two
independent channels.
The two identical electronic circuits are identified as
Channel A and Channel B. Each channel is supplied with
identical data from the aircraft and the engine including
throttle position, aircraft digital data, air pressures,
temperatures and rotor speeds.
Each of the EEC channels can exercise full control of all
engine functions with only one channel exercising full
control at one time while the other channel is in “Back up”
mode. Control alternates between Channel A and Channel
B for consecutive flights, the selection of the controlling
channel being made automatically by the EEC itself
depending on the fault isolation logic.
The two channels are connected by a mating connector
which provides “Cross talk” facility for partial or complete
channel switching, fault isolation logic and exchange of
“Cross link Data”, cross wiring and hardwired discretes
between the channels.
The EEC transmits engine performance data to the
aircraft; used in cockpit display, thrust management and
condition monitoring systems. Aircraft and engine data is
used to give optimum engine performance for different
flight conditions.
.
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Electronic Engine Control Electrical Connections
Harness (electrical) and Pressure Connections Front Face
Two identical, but separate electrical harnesses provide J1 E.B.U. 4000 KSA
the input/output circuits between the EEC and the relevant J2 Engine D202P
sensor/control actuator, and the aircraft interface.
J3 Engine D203P
The harness connectors are 'keyed' to prevent
misconnection. J4 Engine D204P
Note: Single pressure signals are directed to pressure J11 Engine D211P
transducers - located within the EEC - the pressure Rear Face
transducers then supply digital electronic signals to
channels A and B. J5 Engine D205P
The following pressures are sensed: - J6 Data Entry Plug
• Pamb ambient air pressure - fan case sensor J7 E.B.U. 4000 KSB
• Pb burner pressure (air pressure) P3/T3 probe J8 Engine D208P
J9 Engine D209P
• P2 fan inlet pressure - P2/T2 probe
J10 Engine D210P
• P2.5 booster stage outlet pressure
• P5 (P4.9) L.P. Turbine exhaust pressure - P5 (P4.9)
rake
• P12.5 fan outlet pressure - fan rake
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Engine Electronic Control (EEC.)
Overview
The EEC provides the following engine control functions:-
• Power Setting (E.P.R.).
• Acceleration and deceleration times.
• Idle speed governing.
• Overspeed limits (N1 and N2).
• Fuel flow.
• Variable stator vane system (V.S.V.)
• Compressor handling bleed valves.
• Booster stage bleed valve (B.S.B.V.).
• Turbine cooling (10 stage make-up air system).
• Active clearance control (A.C.C.).
• Thrust reverser.
• Automatic engine starting.
• Oil and fuel temperature management.
Note:
The fuel cut off (engine shut down) command comes from
the flight crew and is not controlled by the EEC.
Fault Monitoring
The EEC has extensive self test and fault isolation logic
built in. This logic operates continuously to detect and
isolate defects in the EEC.
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Electronic Engine Control • Air Data Inertial Reference System (ADIRS)
EEC Interfaces The main functions of the ADIRU’s are:
The EEC interfaces with a number of other aircraft systems. • To process pitot and static inputs.
The main systems are as follows:
• Supply air data to other aircraft systems including EEC and
Engine Interface Unit (EIU) to the DMC’s for display.
Two EIU’s are fitted to the aircraft, the main functions are to: Flight Warning Computer (FWC)
• Supply aircraft data to the EEC. Two FWC’s are fitted to the aircraft and their main function is
• Ensure engine to engine segregation. to:
• Select aircraft electrical supplies to the EEC. • Process data for fault annunciation.
• Supply data directly to other aircraft systems. • Generate actions necessary for associated fault.
• Spoilers Elevator Computer (SEC).
Display Management Computer (DMC) • Landing Gear Control Interface Unit (LGCIU).
Three DMC’s are fitted to the aircraft and their main function • Bleed Monitoring Computer (BMC)
are to:
• Flight Control Unit (FCU).
• Receive and process data from other aircraft systems.
• Centralised Fault Display Interface Unit (CFDIU).
• Format and display the data on the 6 display units.
• Multipurpose Control and Display Unit (MCDU).
Flight Management and Guidance Computer (FMGC)
Two FMGC’s are fitted and their main functions are:
• Flight Management, Navigation, performance optimisation
and display management.
• Flight guidance, autopilot and thrust commands to the
EEC.
Other aircraft systems interface with the EEC through the EIU.
These are:
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IAE V2500 Line and Base Maintenance Electronic Engine Control
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Electronic Engine Control (EEC) Data Entry Plug connector with the EEC and hand tighten the connectors.
Purpose Then using the EEC Harness Wrench torque tighten the
DEP connector to 32 lbf in.
The Data Entry Plug (DEP) provides discrete data inputs
to the EEC. Located on to Junction 6 of the EEC. it The DEP links the coded data inputs through the EEC by
provides unique engine data to Channel A and B. The data the use of shorting jumper leads which are used to select
transmitted by the DEP is: the plug pins in a unique combination.
• EPR Modifier (Used for power setting). During the life of an engine, it may be necessary to change
the DEP configuration, either during incorporation of
• Engine Rating (Selected from multiple rating options). Service Bulletins or after engine overhaul, when the EPR
• Engine Serial No. Modifier code may need to be changed.
Location
The data entry plug is located on the channel B side
electrical connectors of the EEC. This is accomplished by changing the configuration of the
During removal/replacement of the DEP it is necessary to jumper leads in accordance with the relevant instructions.
use an EEC harness wrench, as it is imperative that the Service Bulletin V2500-ENG-72-0285 contains the specific
connectors are tight. detail of the process involved for modifying the Data Entry
On fitment of the DEP to the EEC align the main key of the Plug.
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THIS PAGE IS LEFT INTENTIONALLY BLANK
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DATA ENTRY PLUG (DEP)
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Electronic Engine Control
Failures and Redundancy
Improved reliability is achieved by utilising dual sensors,
dual control channels, dual selectors and dual feedback.
• Dual sensors are used to supply all EEC inputs except
pressures, (single pressure transducers within the EEC
provide signals to each channel - A and B).
• The EEC uses identical software in each of the two
channels. Each channel has its own power supply,
processor, programme memory and input/output
functions. The mode of operation and the selection of
the channel in control is decided by the availability of
input signal and output controls.
• Each channel normally uses its own input signals but
each channel can also use input signals from the other
channel required i.e. if it recognises faulty, or suspect,
inputs.
• An output fault in one channel will cause switchover to
control from the other channel.
• In the event of faults in both channels a pre-determined
hierarchy decides which channel is more capable of
control and utilises that channel.
• In the event of loss of either channels, or loss of
electrical power, the systems are designed to go to the
fail safe positions.
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Failures and Redundancy • Note;
In the event of loss of both input signals, loss of either If there is a failure of the thrust reverser control unit arming
channels, or loss of electrical power, the system is valve while the reverser is deployed, the. reverser will
designed to go to the fail safe positions shown in the table remain deployed.
below.
EEC. System Component Failsafe Position
• Fuel Metering Unit
− Metering Valve Torque Motor • Minimum Fuel Flow Position
− Fuel Shut-off Valve • Last Commanded Position
− Overspeed Valve Solenoid • Normal Fuel Flow Position
• Seventh Stage Bleed Valves • Valves Open
• Tenth Stage Bleed Valve • Valve Open
• Combined Active Clearance Control Unit
− High ACC • Valve Closed
− Low ACC • Valve partially (-44%) Open
• Low Compressor (2.5) Bleed Actuator • Valve Open
• Stator Vane Actuator • Vanes Open
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EEC. System Component Failsafe Position
• Fuel Diverter and Back to Tank Valve.
− Fuel Diverter Valve. • Solenoid De-energised (Mode 4 or 5).
− Fuel Back to Tank Valve. • Valve Closed - No Return to Tank (Mode 3 or 5).
• Air/oil Cooler Control Valve Actuator • Valve Open.
• Tenth Stage “Make-up” Cooling Air Valve • Valve Open.
• Thrust Reverser Control Unit. • Reverser Stowed.
• PT2/TT2 Relay Box
− ignition Relays • Ignition ON.
− Probe Heater Relays • Heater OFF.
• Starter Air Valve • Valve Closed.
• Anti-ice Air Valve • Valve Open
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Operation and Control
EEC Power Supplies
The electrical supplies for the EEC are normally provided test power for EEC maintenance.
by a dedicated alternator, which is mounted on and driven During engine starts 28V DC is supplied from the aircraft
by the external gearbox. bus bars until the dedicated alternator comes 'on line' at
Dedicated Alternator approximately 10% N2.
The permanent magnet alternator has two independent Switching between the aircraft 28V supply and dedicated
sets of stator windings that supply two independent, 3 alternator power supplies is done automatically by the
phase frequency AC outputs to the EEC. These EEC so in the event of a total failure of the dedicated
unregulated AC supplies are rectified to 28 volts DC within alternator the EEC is supplied from the aircraft 28V DC
the EEC bus bars,
The Dedicated Alternator also supplies N2 signals for the
EEC. This is provided by the frequency of a single phase
winding in the stator housing as the ‘primary’ speed signal
used by both Channels of the EEC and for the Flight Deck
instrument display of engine actual speed. Should this
signal fail, there is a ‘Back-up’ signal which is derived from
one of the three phase windings of Channel ‘B’ power
generation.
There is no speed signal generation provided by the output
of the coil windings of the Dedicated Alternator Channel ‘A’
power supply.
The EEC also utilises aircraft power to operate some
engine systems: -
• 115 volts AC 400 Hz power is required for the ignition
system and inlet probe anti-icing heater.
• 28V DC is required for some specific functions, which
include the thrust reverser, fuel on/off and ground
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IAE V2500 Line and Base Maintenance Electronic Engine Control
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Dedicated Alternator
Cooling Shroud Location
It is important that the cooling shroud is orientated
correctly for the differing variant engines. The shroud must
be clamped with the arrow on the shroud aligned with the
number ‘1’ indicated position for A5 and A1 applications.
For D5 applications only the arrow on the clamp must align
with the number ‘2’ indicated position.
With the arrow aligned make sure that the dowel on the
shroud engages in the adjacent cooling hole on the casing,
this correctly aligns the cooling air inlet on the shroud with
the cooling hole in the casing. Tighten the nut on the
shroud to hold the shroud firmly in the correct position.
Torque the nut on the alternator shroud to 180 – 220 lbfin
(20 – 25 Nm)
Connect the tube to the alternator shroud and torque
tighten the tube nut to 283 – 310 lbfin (32 – 35 Nm) Safety
the tube with locking wire.
Connect the electrical connectors and torque them to 16
lbfin (1,8 Nm)
If this is not carried out, the cooling airflow may not be able
to enter the stator housing due to the cooling air hole on
the stator being masked by the clamp body of the cooling
shroud.
The diagram below shows both arrangements and their
relevant application.
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DEDICATED ALTERNATOR (A5 CONFIGURATION)
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