Login
Register
| Contents [show] |
FADEC
Full authority digital electronic control
FADEC is dual channel. One channel operates as the in control channel. The other channel acts as a standby FADEC with its outputs disabled. Normal output is via ARINC 429. The active channel is alternated on each engine start. Main FADEC power is supplied by the 28V DC PMA, until 50% N2 when aircraft 28V DC is used. The FADEC sets the correct N1 for a given thrust lever position. Information is gained from 5 thermocouples that sense gas temperature, located in the inlet stream of the LPT. The information is used for ITT indication, hot start logic, and flameout detection. Engine fuel flow is measured within the FCU and the signal also goes to the FADEC and the EICAS.
The FADEC controls the T2 sensor anti-icing, which is powered by aircraft 28V DC, and the ignition system, which is powered by 115V AC 400Hz.
Setting
Main setting is the TLA, and the air data from the engine (N2, P3, ITT, TRAS) and airframe sensors. A reference N1 is then calculated. Control is for N2 or P3 with the thrust levers idle, or N1 above idle.
Protection
- engine speed
- engine temperature
- compressor discharge pressure (CDP)
Start protection
- hot start (inhibited in the air)
- hung start (inhibited in the air)
- no light-off start
A hot start is terminated when ITT >740° by closing the fuel metering valve and shutting off the ignition. The starter driver is not deenergised to allow motoring. To terminate the motoring, the start/stop selector must be turned to STOP.
EICAS messages
ENG 1 T2 HEAT FAIL