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FADEC
Also from: Full Authority Digital Engine Control; Electronic Engine Control; EEC
Each engine has a FADEC (also called the EEC) providing engine management. Each FADEC has two independent channels, A and B, which switch at engine start. The FADEC is powered for 5 minutes after electrical power is applied to the aircraft and then shuts down automatically (to prevent overheating). They can be switched on manually using the ENG FADEC GND PWR switches on the overhead panel in order to check oil quantity. When IGN START is selected on the ENG START selector, the FADECs are powered again through the PCU.
Above 8% N3, the FADEC is self powered. The FADECs have their own magnetic alternator as an internal power source.
Fuel used indications are reset on the ground at engine start.
EPR or N1 can be used for engine control, depending on the availability of air data inputs to the FADEC. N1 is used during reverse operation. EPR = low pressure turbine exhaust pressure (P5) / engine air inlet pressure (P2).
FADEC interfaces with the EIU and gets other inputs from:
- TLA
- ADIRS 1+2
- N1 mode pb
- engine sensors and valve positions
Exceedance protections
- N1, N2 overspeed (the OPU is independent of the FADEC and shuts high pressure fuel shutoff valves at 110% N1 or 117% N2)
- turbine overspeed (closure of high pressure shutoff valve)
- monitoring of EGT during autostart on ground
Idle modes
- Modulated idle: selected in flight, flaps up and gear up, and on ground, reverse not selected
- Approach idle: selected in flight, FLAP 2, FLAP 3 or FULL, or landing gear down
- Reverse idle: selected on ground, reverse thrust selected
MEASTO
Logic that provides progressive thrust for takeoff. Engine acceleration is controlled by an EPR per second rate.
N1 mode
If EPR mode is not available, there is automatic reversion to N1 mode. Autothrust is not available, and α FLOOR protection is lost. The two N1 modes are rated N1 mode and unrated N1 mode. N1 rated mode can also be manually selected.
| N1 Rated Mode | failure of engine pressure data | computed EPR command depends on TLA | amber EPR max index moves to N1 and becomes N1 max |
| N1 Unrated Mode (also called Degraded Mode) | engine + ADIRS loss of temperature or pressure data | N1 a function of TLA and altitude; overboost can occur | no amber max index |