Boeing 747-400 Electrical (SIT4.1) Exam
Questions & Answers (Grade A+)
What does "AVAIL" light indicate on the External and APU PWR
switches? -
correct answer ✅The related power source (APU or EXT) is
plugged in and available and the power quality is acceptable.
What Bus is powered on the ground when APU GEN 1 or EXT PWR 1
is available? -
correct answer ✅Ground handling bus
When is the Main Deck Cargo Handling Bus powered? -
correct answer ✅When the "AVAIL" light is displayed on the APU 2
or EXT 2 switches
What electrical power source would you select if cargo handling is
required? -
correct answer ✅The number one auxiliary or external power
When is Ground Service Bus powered? -
correct answer ✅When AC bus 1 is powered either on the ground
or in flight
, Boeing 747-400 Electrical (SIT4.1) Exam
Questions & Answers (Grade A+)
What is the function of the Standby Power Switch in the auto
position? -
correct answer ✅Allows the main and APU standby busses to be
powered from available sources
Where would you find the Electrical Power-up procedure? -
correct answer ✅Refer to the FCOM, Vol.1, Supplemental
Procedures
What does a Bus Isolation (ISLN) light illuminated indicate? -
correct answer ✅BTB open, AC bus isolated from synchronous bus
What happens when you push a Generator Drive Disconnect (DRIVE
DISC) switch? -
correct answer ✅*Disconnects IDG from engine when above idle
speed *Opens related Generator Control Breaker (GCB)
What condition would automatically disconnect the IDG if not
manually disconnected by the flight crew? -
correct answer ✅Excessively high drive oil temperature
Questions & Answers (Grade A+)
What does "AVAIL" light indicate on the External and APU PWR
switches? -
correct answer ✅The related power source (APU or EXT) is
plugged in and available and the power quality is acceptable.
What Bus is powered on the ground when APU GEN 1 or EXT PWR 1
is available? -
correct answer ✅Ground handling bus
When is the Main Deck Cargo Handling Bus powered? -
correct answer ✅When the "AVAIL" light is displayed on the APU 2
or EXT 2 switches
What electrical power source would you select if cargo handling is
required? -
correct answer ✅The number one auxiliary or external power
When is Ground Service Bus powered? -
correct answer ✅When AC bus 1 is powered either on the ground
or in flight
, Boeing 747-400 Electrical (SIT4.1) Exam
Questions & Answers (Grade A+)
What is the function of the Standby Power Switch in the auto
position? -
correct answer ✅Allows the main and APU standby busses to be
powered from available sources
Where would you find the Electrical Power-up procedure? -
correct answer ✅Refer to the FCOM, Vol.1, Supplemental
Procedures
What does a Bus Isolation (ISLN) light illuminated indicate? -
correct answer ✅BTB open, AC bus isolated from synchronous bus
What happens when you push a Generator Drive Disconnect (DRIVE
DISC) switch? -
correct answer ✅*Disconnects IDG from engine when above idle
speed *Opens related Generator Control Breaker (GCB)
What condition would automatically disconnect the IDG if not
manually disconnected by the flight crew? -
correct answer ✅Excessively high drive oil temperature
