ELECTRONIC ENGINE CONTROL
The Electronic Engine Control (EEC) is an electronic package which
contains all the components necessary for effective automatic control of the
engine and helicopter rotor system. The EEC is installed in the aft electronic
compartment.
EEC FEATURES
• Single channel control computer
• Starting and shutdown supervision
• Auto-start with ITT limiting logic
• Power management
• Independent NF overspeed protection
• Torque limiting logic
• Fault detection and display management
• Cross-talking function
In case of EEC failure, back-up control is achieved by the pilot who manually
adjusts (sets) the FMM.
DESCRIPTION
The EEC consists of two functionally indipendent subsystems:
• The “control subsystem” which provides control of the engine fuel flow.
• The “limiter subsystem” which provides independant hardware
protection against inadvertent power turbine overspeed.
Both subsystems are isolated from each other, including power supplies,
signal conditioning interface and signal inputs.
When engine is running above 40%Ng, the EEC is powered by the
Permanent Magnet Alternator (PMA).
The EEC is powered by the on-side ESS bus via the EEC 1(2) circuit
breaker for engine starting operation and in case the PMA fails.
OPERATION
The EEC monitors all engine parameters and controls the FMM providing
automatic adjustment of the fuel flow delivered to the engine.
The EEC controls fuel flow from start to full power within established upper
and lower limits. The fuel flow is adjusted by a torque motor interface valve,
housed in the FMM, which responds to EEC commands.
In the event of a critical failure of the EEC, a fuel metering manual backup
mode is automatically activated.
In case of power turbine overspeed, the limiter subsystem of the EEC
automatically reduces the fuel flow, indipendently of the EEC fuel flow
control.
EEC LIMITATIONS
EEC is sensitive to high temperatures. When helicopter is powered on the
ground (engines not being started) with high OAT, the EEC circuit breakers
must be disconnected. See RFM, section 1, Limitations.