FADEC

Overview

The Full Authority Digital Engine Control (FADEC) is an electrical system that governs rotor speed, limits engine torque and provides automatic start sequencing and surge protection functions. The FADEC has a hydromechanical backup mode (Manual mode) that only provides NP overspeed protection.

FADEC Power and Control

FADEC Power Source

The FADEC is powered from two sources; the Battery Emergency Bus or a Permanent Magnet Alternator (PMA) located in the engine compartment. The PMA is capable of providing power to the FADEC when NP is greater than 85%. Below 85% NP power is supplied from the aircraft via the Battery Emergency Bus and the FADEC Circuit Breaker Switch.

FADEC Control

FADEC Circuit Breaker Switch

The FADEC Circuit Breaker Switch is located in the Overhead Console Panel and must be placed into the ON position to provide aircraft power to the FADEC during start-up and shutdown.

FADEC Auto/Manual Switch

The FADEC can be switched between Automatic and Manual (Backup) mode using the FADEC Auto/Manual Switch located on the dashboard above the Standby Airspeed Indicator.

RPM Trim Switch

With FADEC in the AUTO mode , the RPM Trim Switch is located on the Pilot Collective Grip and allows adjustment of engine speed (NP) between 95%-105%.

FADEC Modes

Automatic

In Automatic mode the Hydromechanical Unit (HMU) regulating fuel flow to the engine is controlled from the Electronic Control Unit (ECU). The ECU monitors engine and rotor speeds, throttle and collective positions and engine temperatures in order to maintain the set rotor RPM.

When the FADEC is in Automatic mode, the ECU will govern fuel flow when the throttle is above 65 %. If the FADEC is placed in Automatic mode and the throttle is below 65%, the ‘Check Throttle’ advisory will be displayed on the MFD.

During start-up the ECU will govern fuel flow, starter and ignition logic to control NG acceleration and limit engine start temperatures. The FADEC provides an overspeed protection system that will be activated at 124.5% NP and resets at 118% NP. When the overspeed protection system is activated fuel flow will be rapidly reduced until the system resets.

Manual

When placed into Manual mode, the HMU is controlled by the throttle. Only the overspeed protection system remains active in Manual .