Flashcards in Electrical System Deck (55)
What is an RPDU? How many are there?
Remote Power Distribution Unit. 17
What are the 2 distinct power distribution methods?
Primary or Remote.
Direct distribution from the respective AC/DC buses or distribution via the Remote Power Distribution System.
What amperage loads do the RPDU's distribute?
10 amps or less
How many main 235Vac power system buses are there?
How are they designated?
L1, L2, R1, R2
How do the generators power the main AC buses with both engines online?
Each VFSG is connected to a main AC bus
How do the generators power the main AC buses with one engine running and the APU online?
VFSG's power the on side main AC buses, ASG's power the P150 Auxiliary power panel which provides power to the other side main AC buses through the tie bus.
How are the main AC buses powered with external power online?
External power connected directly to 115Vac buses. Main AC buses connected by the bus tie and powered by power converters from the 115Vac buses.
On the ground with only forward external power selected, what powers the 115Vac buses?
115Vac buses powered by external power directly.
What is the BPCU and what does it provide?
Bus Power Control Unit
-Overall load management.
-Electrical power transfers.
-Flight deck control and indications.
What power sources can the aircraft use for engine starts?
VFSG's, ASG's or external power.
Aft external power can only be used to assist a start for which engine?
The right engine
How many starters are needed to start the APU?
How many starters are needed to start an engine?
Are both ASG's required to maintain the electrical load in flight?
Yes, but there will be load shedding.
What are the primary and backup power sources for the airplane brakes?
Primary: 28Vdc system
Backup: Main battery
On which side of the aircraft are the external power receptacles located?
Left side of the fuselage
How many external ground sources are required to energize the "Ground Handling Mode"?
In flight, when will the RAT automatically deploy?
-Both engines have failed
-All three hydraulic system pressures are low
-Loss of all electrical power to the captains flight instruments
-Loss of all four EMP's and faults in the flight control system occur on approach
-Loss of all four EMP's and an engine fails on takeoff or landing
Which cockpit displays are powered during RAT operations?
-Captain inboard DU
-Captain outboard DU
What major systems are not available on "In-air RAT only mode, Standby Power)?
Flaps, Slats, Stabilizer trim, Packs, Thrust reversers, Auto speedbrakes, HUD, WIPS, (window heats, autothrottle, TAT, TAP, HF radios, SATCOM, TCAS, GPWS, XPDR, WX radar, external lighting, LNAV/VNAV, FMC predictions)
How is load shedding determined by the bus power control unit?
Loads are shed in order of priority to stay within the capacity of the available power sources.
What equipment is energized in the "In-air Battery only" mode (Standby Power)?
Captains flight instruments and other essential equipment for flight controls, navigation and communication.
-CPT and Lower DU's
-ISFD, ECL, FMC (Limited)
-MCP, Autoflight & Autopilot (Limited)
-DSP L, MFK L, CCD L
-CPT/FO ACP & Interphone
-VHF L, TCP L, CCR L
-IRU, AHRU, INR, PFC
-ENG/APU fire detection
How can load shedding be monitored in the aircraft?
Electrical synoptic shows a list of systems affected by load shedding. Affected system synoptic (AIR, FUEL, HYD) also indicate equipment that is inhibited or shed.
What does the main battery power directly?
Hot battery bus
What are the primary and backup power sources for the flight control computers?
Primary: 3 engine driven Permanent Magnet Generators (2 left eng, 1 right eng)
Backup: Airplane 28Vdc system, airplane battery and dedicated batteries.
What does the APU battery power on the ground?
APU start and Navigation lights (during battery only towing)
How can the circuit breakers be accessed in the aircraft?
Through the Circuit Breaker Indication and Control (CBIC)
What is the maximum number of load shed items that can be displayed on the electrical synoptic?
Does "Ground Handling Mode" have priority over "On-ground Battery only mode"?
Yes, initialized regardless of battery switch position