B757 Electrical

Question 1

What items are powered by the Standby Power System

Answer 1

Right IRU

Fuel indicators

Manual Pressurization

Master Warning Lights

Gear lights

Standby Engine Instrument

Electrical Standby Instrument System

Capt’s Marker Beacon

Alternate Stab Trim

Manual Speed Brakes

Flaps Handle serves as indicator

Fuel Control Switches

Left VHF (PA and Intercom)

Center ILS and Control head

Engines/APU Fire detection and protection

Question 2

APU Generator (APU GEN) Control Switch

Answer 2

ON (bar in view) - arms APU generator control breaker to close automatically

OFF (bar not visible)
• opens APU generator control breaker
• resets fault trip circuitry

Question 3

APU Generator OFF light - amber

Answer 3

1. APU generator control breaker is open because of a fault with APU running
2. APU generator control switch is selected OFF

Question 4

Bus Tie Switches - Auto

Answer 4

1. Arms automatic AC Bus Tie Circuits
2. Arms automatic DC Bus Tie Circuits
3. Arms automatic flight instrument transfer bus Circuits

Question 5

Bus Tie Switches - Off

Answer 5

1. Commands AC Bus Tie open
2. Commands DC Bus Tie open
3. Commands the flight Instrument Bus Tie open
4. Resets Fault trip circuitry

Question 6

AC Bus Isolation ISLN lights

Answer 6

1. Fault Tie has occurred, automatically opening the AC bus Tie breaker
2. Bus Tie switch is OFF

Question 7

Generator Control GEN CONT Switches

On

Answer 7

On - arms the generator control breaker to close automatically when Generator power is available.

Question 8

Generator Control GEN CONT Switches

Off - bar not visible

Answer 8

• opens the generator control breaker

* resets the fault trip circuitry

Question 9

External power ON light - white

Answer 9

External power is powering the buses.

External power is the 800 lb gorilla. Takes priority control of all buses when turned on

Question 10

External power available (AVAIL) light - white

Answer 10

External power is plugged in and power quality is acceptable

Question 11

Utility Bus Switches

Answer 11

ON - bar in view

Connects utility and galley buses to main AC bus

OFF - bar not visible
• disconnects utility and galley buses from main AC bus
• resets overload load shed circuitry

Question 12

Utility Bus OFF lights - amber

Answer 12

Utility and galley buses are unpowered

Question 13

GEN DRIVE DISC switches

Answer 13

Push -
• Disconnects generator drive from the engine
• Requires maintenance action on the ground to reconnect the generator drive

Question 14

Generator DRIVE Lights - amber

Answer 14

1. Generator drive oil temp is high

2. Generator drive oil pressure is low

Question 15

Battery (BAT) switch - ON

Answer 15

Allows APU to be started
Powers airplane when AC power is removed or lost.
STDBY and battery busses are powered

Question 16

Battery OFF light

Answer 16

The battery switch is off

Question 17

DISCH light - amber

Answer 17

The main battery is discharging

Question 18

Standby (STBY) Power Selector

Answer 18

OFF - STBY busses are unpowered
AUTO - STBY busses transfer to battery power if normal AC power is lost.
BAT - the STBY busses are powered from the main battery

Question 19

Standby Power Bus OFF light - amber

Answer 19

STBY AC or DC bus not powered

Question 20

Electrical Concept

Answer 20

1. Power priority
2. Detect and isolate faults
3. Prevent paralleling
4. Permits CA and FO instrument switching
5. . D.C. bus ties close
6. Resets Fault Trip circuitry
7. One Gen can power both main AC buses.