FADEC/MC Propulsion Flashcards
F___ A____D____E____C____
Full authority digital electronic control
FADECS interface with
Other engine systems, controls, air data and propeller
The FADECs provide
Monitoring and control of the propeller and engine
Forward thrust— when power levers are forward of FLT IDLE, FADEC schedules __ as a function of __. Propeller speed is maintained at __%
Torque as a function of power lever angle
100%
Ground range— when power levers are between FLT IDLE and reverse, FADEC schedules ___ as a function of ___ and prop is maintained at
Blade angle as a function of power lever angle.
99%
Reverse thrust— when power levers in the reverse range, FADEC schedules ___ as a function of ___. Prop maintained at
Torque as a function of power lever angle.
101 %
GRND IDLE Blade Angle vs calibrated airspeed
Outboards
Above 110: 1 degree
110-90: 1 –> 8 degrees
70-50: Back to 1 degree
GRND IDLE Blade Angle vs calibrated airspeed
Inboards
-2 degrees at all airspeeds down to 70
70-50: Back to 1 degree
FADEC autofeather request- FADEC requests MC permission to autofeather if the power lever is FLT IDLE or above with any of the following:
1.Loss of propeller control (high power and NP below 73)
- At low power settings, low NG (less than 69 percent)
- At high power settings, low engine HP( less than 74% commanded) and decelerating NG (greater than 500 rpm per second)
MC Autofeather Permission —
Outboards always have permission (supports low min control speeds)
Inboards granted after 2 second delay as long as aircraft is below 15,500 and all other engines running normal. Otherwise windmills at 100%, ensures at least one will windmill if all 4 fail.
FADEC Auto Ignition and Automatic Engine shutdown —if prop autofeathered:
FADEC attempts to maintain gas generator core speed at idle RPM
If flameout detected, FADEC initiates ignition and monitors for relight
If relight doesn’t occur before NG decreases below 56 percent, FADEC auto shuts off fuel to engine
MC auto Engine shutdown
If all pwr levers have been approximately equal for 5 seconds, the MC looks for one engine HP more than approximately 1100HP above others, AND
NG not significantly decelerating, NP greater than 60%
MC commands FADEC to shut engine down
(Disarmed if ATCS switch off)
Propeller synchrophasing
FADEC provides automatic propeller synchrophasing,
FADEC A for engines 2 & 3 are only FADECS used as master
Prop underspeed protection:
Software incorporated to protect against underspeed, overrides control logic to decrease blade angle
Reversionary NG control
Reversion control mode allows continued safe flight with both torque sensors failed
Bases fuel scheduling on NG instead of normal torque. Automatically engaged by FADEC. Requires closer monitoring
Available HP reduced by 40%
Automatic start control
FADEC automatically controls starter, ignition, fuel and propeller systems during start.
Only difference in ground vs air is the FADEC won’t shut down a stagnated start in air
Manual feathering only functions with
Start switch to stop, or if PWR levers are at GND IDLE and low-speed GND IDLE is selected.
AUX Feather pump is turned on when:
Propeller control switch positioned to feather
Aux feather pump automatically shuts off after
20 seconds
If NP exceeds 104.5
Propeller overspeed governor diverts pump oil away from PCU to allow blade counterweights to increase blade angle to control overspeed
If NP exceeds 106
FADEC reduces fuel flow
NG exceeds 109 or NP exceeds 119
FADEC shuts down engine
ATCS
ATCS limits asymmetric thrust between two outboard engines at slow speed in order to reduce minimum control speeds.
