7ER Electrical Flashcards
(40 cards)
Location/Function of GROUND SERVICE switch?
On forward flight attendant panel
Powers the Ground Service bus from Ext or APU power via the Ground Handling bus
(only useful if ext power is plugged but not turned on in flight deck, otherwise Right AC bus will power the Ground Service bus)
What general equipment is powered by the Ground Service bus?
Battery chargers (main & APU)
Misc cabin & system loads (interior things for getting the plane ready)
What equipment is powered by the Ground Handling bus?
Fueling system
Cargo doors, equipment, and lighting
Potable water filling
(i.e. external servicing of the aircraft)
What are the main sources of AC power?
Left and Right IDGs
APU generator
External power
When does the HDG activate automatically, and how is it powered?
Activates when both LEFT AC and RIGHT AC busses are unpowered and appropriate hydraulic system pressure is available
757: powered by Left hyd system
767: powered by Center hyd system
Location/Function of BAT switch?
Left Overhead
OFF (no light) - Batteries are off, only hot bus power remains
ON (ON light) - Batteries are on, APU can be started, a few annunciators are powered and can illuminate
What does the OFF light in the BAT switch indicate?
The switch is off with normal power on
Location/Function of the STBY POWER selector?
Left Overhead
OFF - Standby busses are unpowered
AUTO - The Standby busses transfer to battery power if AC power is lost
BAT - Standby busses are powered by the main battery, and the main battery is not charged
Which electrical indicator lights are not powered if only battery power exists?
The BAT switch OFF light and the UTILITY BUS OFF lights
How can the batteries be charged with only external power connected but not turned on (AVAIL light in switch)?
The Ground Service switch on the Flight Attendant Panel must be pressed to connect the Ground Handling bus to the Ground Service bus, which powers the battery chargers
How is the Ground Services bus powered when External power is connected and turned on (ON light in switch), or APU power is applied?
The Right AC bus
With normal AC power applied, what powers the Hot Battery bus?
The Main Battery charger
What is powered by the Hot Battery bus?
Things that need continuous power, such as:
Clock Timer
APU and Spar fuel valves
Fire extinguisher bottles
Parking brake valve
With AC power established, what powers the Battery bus?
The Left DC bus, with the main battery as a backup
Can the batteries be charged with only one DC bus functional?
No, battery chargers are shed
Function of the GEN CONT switch?
ON - arms the Generator Control Breaker to close and power its respective main AC bus when generator power is available
OFF - opens the Generator Control Breaker, resets fault trip circuitry
How long will the battery last on standby power?
30 minutes
90 minutes on the 753
How is landing gear and flap extension affected is battery power is lost without an operating HDG (767 only)?
Flaps and gear cannot be extended
Where to find the list of systems inoperative when on HDG power?
QRH Chapter 6 (AC BUS OFF procedure)
What does the illumination of a UTILITY BUS OFF light mean?
The affected utility bus has been load shed. The associated galley bus will also have been shed
What conditions can cause a utility bus to load shed?
Both thrust levers advanced with a single power source (on ground)
An overload
Single-generator operation (in flight)
Starting engines with the APU providing electrical power (while ENG START selector is in GND)
When one engine is running, only the bus on the other side will shed during the second engine start
How would you know if a galley bus has been load shed?
From a report by the cabin crew, since there is no flight deck indication and a galley bus can be load shed without the corresponding utility bus shedding
What does an EXT PWR AVAIL light indicate?
External power is plugged in and power quality is acceptable. The ground handling bus is powered
What does an EXT PWR ON light indicate?
External power is powering at least one main AC bus
