DC System Flashcards
Learn about the DHC8 electrical system
What does the #1 or #2 DC GEN caution light tell you?
The respective DC generator is off-line
What does the L TRU or R TRU caution light tell you?
The respective TRU is off-line
With the AUX, main and battery master on, as well as the bus tie closed, which buses are powered?
The main and AUX battery buses
L and R essential buses,
L and R main feeder buses
Note the secondary feeder buses are not powered
If the AUX battery indicator on the overhead panel had 0.30, what does this tell the pilot? How would the pilot know if it was discharging?
The battery is either charging or discharging at 30% of the maximum rated capacity.
If there was a flashing - it is discharging.
The Battery bus supplies continues 24v power for what?
Fire extinguisher discharge circuits Emergency fuel/hydraulic shut-offs APU manual fire discharge circuit Dome lights boarding lights Emergency lights control box PA system through a relay in the emergency lights system
Can batteries be charged by DC external power? Are there any special requirements for this?
Yes but only the main battery with Mod8/2066, however battery charge rate and temperature must be continually monitored.
How many temperature sensors does each battery have? What are they connected to?
2, one connected to the battery temperature indicator, the other to the MAIN BAT HOT or AUX BAT HOT warning light.
If a battery temperature sensor fails how is the pilot notified?
A yellow light illuminates adjacent to the temperature indicator.
If the battery temperature display fails, how is the pilot notified?
A single yellow light segment appears at the 60 degree C mark on the affected battery temperature scale.
If the MAIN BATTERY caution light appears, what does this tell the pilot?
The main battery is disconnected from the right main feeder bus
Where are the GCUs and BBPU found in the aircraft?
Below the co-pilots circuit beaker panel
The DC generator is mounted on which gearbox?
Accessory gearbox
How can a pilot shut down a TRU?
By pulling the circuit beaker in accordance with a QRH checklist.
If the #1 or #2 DC GEN HOT caution light appears, is the generator automatically taken off-line?
No, the generator needs to be manually taken off-line.
If both DC generators fail, will the system still be powered? Is there enough power?
Yes, the DC logic will close the left and right bus tie contractors allowing the secondary feeder buses to power the system.
The secondary feeder buses struggle so power is slowly being drawn from the batteries.
What caution lights indicate a ‘ loss of generated power’
Both DC GENs and both AC GENs
Both DC GENs and either one or both TRUs
What does the BBPU do? How does it work?
It detects bus faults by monitoring the GCUs for generator over current conditions.
It responds in 2 stages, first taking the DC bus off-line opening the main and both secondary bus ties (DC BUS caution illuminates). If over current still exists after 7 seconds, the BBPU then signals the GCU to shut down the affected generator and isolates the affected battery from the faulted main feeder bus.
DC BUS, #1 DC GEN, AUX INV and AUX BATT
DC BUS, #2 DC GEN, and MAIN BATT respectively indicate what faults? What checklist should be called for?
Left and right Main DC bus fault respectively.
Call for MAIN DC BUS FAULT checklist.
Following a MAIN DC BUS FAULT, how do you know if the generator or bus caused the problem?
As per QRH reset the main bus fault reset. if DC BUS caution light goes out and stays out the generator was the issue. If the DC BUS caution light stays on, the DC bus was the problem so you’ll lose the services from the respective bus.
When external DC power is applied, what protects the DC System? When will the protection Activate? How is it powered
An over voltage protection relay automatically disconnects external power from the system when external power at the receptical exceeds 31.5 volts.
The relay is powered by the essential bus which is why the battery master must be on prior to connecting ground power.
Which bus does the APU feed power to?
Right main feeder bus. This bus can then power the left main feeder bus, both essential buses and both secondary feeder buses
During ground operations, what is the maximum DC generator loadmeter reading?
Is the value ever allowed to be exceeded
0.7. Yes, for internal battery starting, the load may be exceeded for up to 1 minute.
What happens when you switch the battery master on?
The essential buses are powered. The main bus powers the right essential bus and the AUX battery powers the left. However either battery can power both essential buses.
It also enables the main battery to power the right main feeder bus when the main battery is is selected on.
What are some things powered by the essential buses?
Advisory and caution lights EHSI 1 and EADI 1 and SYM gen1 AHRS 1 Eng ECUs Eng Instruments (Torque, ITT, Np, Nh, oil T and P) VHF Com 1 and nav 1 HYD quan and ind Hot BATT bus stuff Rad alt
