Electrical Flashcards
Identify the location of the GROUND SERVICE bus switch.
• In the cabin on the forward flight attendant panel.
Recall the main AC power sources.
- The Left and Right Engine Integrated Drive Generators (Engines Operating)
- The APU Generator
- External Power
Recall when the hydraulic driven generator activates (HDG equipped aircraft only).
• The Hydraulic Driven Generator (HDG) activates automatically when both the Left and Right main AC busses are unpowered.
- The HDG is powered by the Left hydraulic system on the 757 if installed.
- The HDG is powered by the Center hydraulic system on the 767-300 and ER if installed.
List the components powered by the ground service bus.
The Ground Service Bus powers:
• The main battery charger.
• The APU battery charger.
• Miscellaneous cabin and system loads.
Identify how the ground handling bus can be powered.
Ground Handling Bus
• The ground handling bus can be powered only on the ground and only from the APU generator or from the external power source (AVAIL light illuminated)
Note:
To accept late bags after pushback, the 757 must have APU power to operate the cargo doors.
To accept late bags after pushback, the 767 must have APU power to operate the right side cargo doors.
The manual bulk cargo door on the 767 can be used with no power requirements.
Explain the function of the battery (BAT) switch
Unpowered airplane on the ground:
BAT switch off (ON not visible)
• Turns battery power off.
Unpowered airplane on the ground: BAT switch ON • Turns battery power on. • Allows the APU to be started • A few annunciator lights illuminate
Powered airplane on the ground or in flight, and AC power is removed or lost:
• The battery bus and standby busses are powered.
Recall how long the battery will last on standby power
• 30 minutes minimum powering standby AC and DC busses.
Note: The 757-300, the MAIN and APU batteries are paralleled for a standby power operation of 90 minutes.
Recall how landing gear extension and flap operation are affected if battery power is lost on a 767 without an operating HDG.
• The flaps and gear CANNOT be extended.
Note:
- The normal landing gear and flap extension methods require Center hydraulic pressure. Pressure will not be available.
- The alternate landing gear and flap extension methods require electrical power. Power will not be available.
Identify where to find the major systems NOT available when operating on HDG power.
• The QRH identifies the major systems NOT available when operating on HDG power.
Recall the meaning of an illuminated L/R UTILITY BUS OFF light and the conditions that cause the utility busses to load shed.
Utility Bus OFF lights
• Illuminated (amber) – the utility and galley busses are
unpowered.
Utility Bus load shedding
• Both thrust levers advanced on the ground with a single power
source.
• Overload.
• Single generator operation in-flight.
• Starting engines with the APU providing electrical power
Recall that galley power can shed without illumination of the______________________. (Utility busses are still powered)
L / R UTILITY BUS OFF lights
Recall what an EXT PWR AVAIL and an ON light indicates.
External Power Available (AVAIL) light
• Illuminated (white) – external power is plugged in and the power quality is acceptable.
External Power ON light
• Illuminated (white) – external power is powering the busses.
Recall what is indicated by an AC BUS OFF light.
AC BUS OFF lights
• Illuminated (amber) – the respective AC bus is unpowered.
Explain the meaning of a generator DRIVE light
GEN DRIVE lights
• Illuminated (amber) –
- The generator drive oil temperature is high
- The generator drive oil pressure is low.
Explain the meaning of an illuminated APU GEN (generator) OFF light on the overhead electrical panel. (Switch ON)
- The APU generator breaker is open because of a fault with the APU running.
- The APU GEN switch is selected OFF.
