ELEC BACKUP SYS
π Sources: QRH 6.3 (R53), FCOM 6.30.1
1. QRH Reference & Condition
- QRH Section: 6.3
- EICAS Level: Advisory
- Condition: The backup power system is failed.
2. Non-Normal Checklist
CAUTION
Attempt only one reset per flight (each generator).
| Step | Action |
|---|---|
| 1 | L BACKUP GEN switch β¦ β¦ Off, then ON |
| 2 | R BACKUP GEN switch β¦ β¦ Off, then ON |
3. System Explanation
This message indicates the entire backup power system has failed β both left and right backup generators. (FCOM 6.20.7)
Operational Impact:
- No backup AC power available for transfer busses
- Autoland not available (APP mode requires backup system to power R transfer bus, R main DC bus, and F/O flight instrument bus independently)
- If both IDGs fail, no backup power to fall back on β standby system (RAT/battery) only
WARNING
With ELEC BACKUP SYS, autoland capability is lost. CAT II/III approaches are not available.
4. Related EICAS Messages
| Message | Description |
|---|---|
| ELEC BATTERY OFF | Battery switch is OFF |
| ELEC BUS ISLN L, R | Bus tie breaker open |
| ELEC CABIN/UTIL OFF | Cabin/utility power switch OFF |
5. Cross-References
- Electrical System β Backup AC system architecture
- ELEC BACKUP GEN L, R β Individual backup generator failure
- ELEC AC BUS L, R β AC bus unpowered