View Full Version : FADEC ?

7th Aug 2001, 15:26
Can anyone explain what FADEC is?

7th Aug 2001, 15:40
The FADEC (Full Authority Digital Engine Control) is your engine's big boss. On the A320, there are 2 FADECs (one per eng).

During auto starts, the FADEC controls the start valves, the igniters, HP & LP fuel valves, FF, etc. The FADEC also calculates N1 rated limits & provides engine protection.

As its source of power during the flight, the FADEC uses individual, eng-driven alternators, until N2 falls below 15% on shutdown.


7th Aug 2001, 16:50
So in other words it is a modern FCU? If so, how does it differ from a FCU?

7th Aug 2001, 17:53
FADEC is the "fly by wire" of engine controls.
Unlike PMC or EEC there is no cable linking your thrust lever to the control unit in the engine.
Other than that its just an advanced FCU. More efficiently controls fuel flow, variable guide vanes etc.
Oh, and the best bit, when you line the thrust levers up, both engines will produce exactly that same amount of thrust, no matter what. No more staggering the thrust levers!!

7th Aug 2001, 23:03

There seems to be a common confusion. The FADEC is not a physical unit. FADEC is the name of the system which includes many components. The FADEC system provides (CFM56-5 engine):
-control the engine fuel and geometry
-optimize engine clearances
-automatic and manual starting
-engine power management
-control of reverser
-Airframe-engine integration
-Fault tolerance
-Maintenance data
The most important unit (the brain of the system) is the ECU - Electronic Control Unit. In CFM56-5 engines it controls the engine variables:
-Fuel metering valve
-Variable Stator Vanes
-Variable bleed valves
-Rotor active clearance
-Low pressure turbine clearance
-High pressure turbine clearance
-Thrust reverser
-Starter air valve
-Burner staging valve
-Fuel Return Valve

On the flight deck, the ECAM engine warning display information N1,EGT,N2,FF and warning messages are provided by the ECU which processes the information from several sensors.


8th Aug 2001, 12:56
"Unlike PMC or EEC there is no cable linking your thrust lever to the control unit in the engine."

It really depends on the aircraft, HP....

The 747-400's with RR's for example, have EEC's (mounted on the engines), but they have no mechanical cables going from the cockpit to the engine. The EEC's are the rough equivalent of the ECU's mentioned in "delarocha"'s post.

However, I am told that the RR engine management system falls outside the category of "FADEC" as there are a few engine components still not under the control of the EEC.


8th Aug 2001, 16:46
Qavion, your informant was quite correct.

The 747-400 with Rollers has FAFC (Full Authority FUEL Control) units which are not true FADECs but a sort of half way house.
They, obviously, control the fuel metering valve and also the fuel shut-off and engine air start valves but only monitor the positions of the guide vanes and bleed valves.
The Trent engine series has true FADECs however.