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39 Cards in this Set
- Front
- Back
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How many generators on the aircraft and what amperage / voltage? |
4 engine-driven generators (400a / 28V DC) 1 APU starter-generator (400a / 28V DC) |
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How many batteries on the aircraft? (Not including emergency, flashlight, etc) |
Main: 2 NiCad batteries (44 amp-hour, 24V DC) Backup: 1 lead acid battery (5 amp-hour, 24V DC) |
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What is the proper amp/volt setting for ground power? |
1600 amps, 28.5 volts |
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What systems automatically control the logic of the electrical system? |
Electrical Distribution Logic (EDL), and Generator Control Units (GCUs) |
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How many channels is the EDL divided into? |
Two channels. (Channel 1: DC bus 1, shed bus 1, essential DC bus 1, and hot bus 1. Channel 2: DC bus 2, shed bus 2, essential DC bus 2, and hot bus 2) |
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How is the EDL powered? |
By the backup hot bus. (Backup hot bus is connected to DC bus 1 via the backup essential bus.) |
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What are the primary functions of the EDL? |
1. To protect electrical components 2. To distribute available power in the most efficient way 3. Automatic load-shedding |
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When will the EDL command the system to operate as two independent networks? |
When 4 or more generators are online. |
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How many generators are required for shed buses to be powered in flight? |
At least 3. (This is sometimes called the Rule of 3) |
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Which buses are powered in the event of a loss of all generators? (Electrical Emergency) |
The essential buses, hot battery bus, and central bus. (Powered by the main batteries) |
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How long will batteries provide power in an electrical emergency? |
40 minutes, including 3 APU start attempts. (Can be extended to 45 minutes if Pitot 3 Heat is turned off - avoid icing conditions.) |
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Which displays are available in essential power mode? |
EICAS, RMUs 1 and 2, and Standby Instruments |
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Is DME available in essential power mode? |
No. (VOR / LOC approaches may be flown if DME is not required) |
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What does the EICAS warning ELEC ESS XFR FAIL mean? |
The EDL has failed to properly configure the plane to essential power following the loss of all generators. (QRH will tell the pilot to push the guarded ESSENTIAL POWER button.) |
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What would you know if you lost all generators and all displays were still powered? |
The EDL has failed to properly configure the plane to essential power mode. (QRH will tell the pilot to push the guarded ESSENTIAL POWER button.) |
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What does the guarded ESSENTIAL POWER button do? |
It overrides the EDL logic and automatically transfers to electrical emergency configuration. (Ensures that batteries are powering only the essential buses and batteries are isolated from the network.) |
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When are shed buses available on the ground? |
AUTO mode: At least 3 generators on or GPU. OVRD mode: At least 1 generator or GPU. |
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When will the Ground Service Bus be energized? |
Batteries 1 and 2 OFF, and GPU connected (but not selected) (Cockpit dome, courtesy, galley, cabin, lav, bagg, and service compartment lights) |
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Where are the main batteries located? |
In the forward avionics compartments in front of the CA. |
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Where is the backup battery located? |
In the forward avionics compartment in front of the FO. |
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What is the purpose of the backup battery? |
To provide stabilized power for the GCUs protective function and the EDL. (In case of short-circuit or near zero voltage condition.) |
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When is the backup battery charged? |
When the system is powered by a generator and BATT 1 is in AUTO. |
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What protects the backup battery from discharging? |
A diode. (Diodes allow one-way flow of power.) |
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Will the GPU charge the batteries? |
No. (Battery Contactors 1 and 2 automatically open when the GPU is supplying power.) |
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What does ELEC EMERG. ABNORMAL mean? |
The EDL has configured for an electrical emergency when not required. (Batteries are isolated from the DC network, are powering essential and central buses, and are not being charged.) |
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What does the GPU AVAIL inscription mean? |
That a GPU is connected, not necessarily that the power is reliable. |
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What voltage should be checked on the GPU before selecting it? |
26.0 - 29.0 V |
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Will the Shed Bus OVRD work in flight? |
No. (3 or more generators are required for the shed bus to be powered in flight.) |
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What does the BACKUP battery button on the overhead do? |
Disconnects the backup battery from the system when released. (BACKUP BATT OFF BUS message will display) |
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What does the BUS TIES OVRD switch do? |
Bus Tie Contactors are kept closed (1 network) regardless of EDL logic, provided no over-current is detected by one of the 5 GCUs. |
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What does the EICAS message GEN 1 (2,3,4) OVLD mean? |
GCU detect current > 400 amps. |
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Why is it that only BATT 2 can be used for APU starting? |
BATT 1 is automatically isolated from the network during APU starts to provide stable power for voltage sensitive equipment (AHRS). |
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What is the power source for the Emergency Lights? |
4 dedicated batteries, providing 15 minutes of power. |
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When will the Emergency Lights batteries charge? |
In the ARM mode. (In this mode, Emergency Lights are OFF and will come on automatically in electrical emergency.) |
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Why will the nose gear doors open in an electrical emergency? |
The solenoid which keeps the nose gear door hydraulic lines pressurized is on DC Bus 2. |
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What is the source of AC power? Where is it connected. |
One AC inverter is connected to DC Bus 1. (250 volt-amp / 400 Hz, single-phase static inverter. Converts 28V DC to 115V AC) |
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Which items use AC power? |
TCAS, EGPWS, and windshear systems. |
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When does power from the engine-driven generators become available? |
When the engine N2 is at 56.4%. |
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When does power from the APU generator become available? |
When the APU RPM is at 95% for 7 seconds. |
