B-777 Overhead Panel Switches

Question 1

ADIRU

Answer 1

1. Requires batt bus power and ADIRU switch to be on
2. If off, must complete full realignment before the airplane can be moved
3. If electrical power is removed and BATTERY switch is switched OFF, the hot battery bus continues to supply electrical power to the ADIRU. ON BATT light illuminates, and the horn in the landing gear wheel well sounds to alert maintenance personnel that the ADIRU is on battery power.
4. When ADIRU is switched OFF, it remains powered for a few seconds
5. In flight, system logic prevents the ADIRU from becoming unpowered if the ADIRU switch is inadvertently switched OFF

*PREFLIGHT - OFF for 30 seconds, then ON
Verify ON BATT light is extinguished
Verify OFF light is extinguished

Question 2

THRUST ASYM COMP

Answer 2

1. AUTO - Thrust asymmetry compensation operates automatically if a thrust asymmetry condition is detected
2. OFF - TAC has been automatically or manually disconnected

*PREFLIGHT - AUTO
Verify OFF light is extinguished

Question 3

PRIMARY FLIGHT COMPUTERS Disconnect Switch

Answer 3

1. DISC - Disconnects the primary flight computers (PFCs) from the flight control system and puts the airplane in direct mode.
   AUTO can be reselected to attempt restoration of the secondary or normal mode operation
2. AUTO - flight control system operates in the normal mode
   system faults automatically cause the system to switch to the secondary or direct modes

*PREFLIGHT - Guard closed
Verify DISC light is extinguished

Question 4

DISC Light

Answer 4

Illuminates amber if the PFCs are disconnected automatically or manually and the system is in the direct mode

*PREFLIGHT - Verify DISC light is extinguished

Question 5

BATTERY SWITCH

Answer 5

ON -
On the ground, no AC power:
1. Some annunciator lights illuminate

2. Allows APU to be started

On the ground, after AC power is disconnected or lost:
1. Standby busses and emergency

2. Left inboard, outboard, and upper center displays, and left CDU are powered.

OFF - while on the ground, the battery bus is not powered

OFF light illuminates amber when the battery switch is off and the airplane has AC power.

*PREFLIGHT - BATTERY SWITCH - ON
Verify OFF light is extinguished