Why is the primary electrical system, and what is it used for?
- The primary electrical system is a 28-VDC generator system
- It is used for inverter input and for powering the electronic equipment and undercarriage
What does the DC system consist of/ is responsible for?
The DC system consists of generation, distribution, storage, control and monitoring of DC power
What is the AC system responsible for/ consist of?
The AC system consists of inverters, power distribution, control and monitoring of AC power
What is the DC power supplied by
Is is powered by a single 24 volt battery which is charged throughout flight by two starter generators which are both 250 ampere and are 30 volt and regulated to 28.25 volt by the GPU to ensure continuous charge to the battery through flight.
What supply’s AC power for engine instruments and avionics
Either one of the two inverters
-each generator is capable of supplying power to all systems necessary for normal operations as the inverters invert the current from DC to AC which allows the engine instruments and avionics to be powered.
However the battery if it is the only source of power has a limited life (like when just the battery is turned on during preflight)
DC power:
How many volts?
How many ampere hour?
What is it made of?
24 volt
42 ampere hour
Sealed lead acid gel cell battery
Where is the DC battery located?
In the right wing center section forward of the main spar
What does the hot battery bus provide power for?
For essential equipment and the cabin threshold light circuit when the battery and generators are not on
What is the main bus controlled by?
Routed via battery relay, controlled by battery on/off switch on pilots left subpanel
The battery ammeter provides a charge/discharge rate of how many ampere?
+-60 amps
What range should the battery ammeter charge rate be within for takeoff
0 to +10 amps for takeoff
Following a battery powered engine start the battery recharge current is very high and causes what annunciation?
Battery charge annunciator illuminates (once the battery approaches full charge the annunciator will extinguish)
Note: battery is typically used for first engine then when the first engines generator is online the 2nd engine is started with the generator (cross generator start) this is more efficient and results in cooler engine temps
Generators:
How many generators?
How many volts are they rated at?
How many volts are they regulated to?
How many ampere
Do they provide AC or DC power
Can either one provide entire electrical load?
2 generators
Each 30 volts rated
Each regulated to 28.25 volt (+-.25)
250 ampere
Provide DC power
Yes either one can provide entire electrical load
What do generator load meters indicate and where are they located
They indicate how many amps the generator is producing as a % of 250 amps.
-Located overhead
Note: there is two readings on the loadmeters. One being the amps %
And the second one being a meter is indicate bus voltage (which read 0 to +30volts, and it says “push for volts”)
Distribution:
The battery is connected to the hot battery bus which supplies power for what?
Remember by: REGAT BFF
- RNAV memory
- External light power
- Ground communication
- Auxiliary DC bus
- Threshold lights
- Battery relay
- Firewall shutoff valve
- Fire extinguisher system
Current limiters purpose?
Function: Its sole job is protection. It protects the main electrical buses and the opposite generator from damage if a massive short circuit occurs.
(Is a fuse that melts when the amps exceed the current limiters rating, for example 250amps, so it protects the electrical system from failing or a fire occurring
How many sub buses are there that are fed by both the L and R generator buses?
4 (labeled number 1-4 dual fed buses)
Each sub bus is fed from either side through a 60 amp current limiter, a 70amp reverse diode an a 50amp circuit breaker
A reverse diode- prevents the current from reversing
The 50amp circuit breaker is lower than the 60 amp current limiter so that if the amps get high in flight and reach 50amp then the circuit breaker will pop and th pilot can reset it whereas if it reaches 60amp then the current limiter is a fuse which will melt and must be fixed on the ground so it’s a protection system
Ground power receptacle is located where?
Under the right wing, outboard of the nacelle
The relay in external power circuit will only close under what conditions?
- Ground power source polarity is correct
- BAT switch in ON
- GPU voltage is not greater than 32 volts
Note: caution light labeled “EXT PWR” is provided to show ground power connected
Caution- never connect an external power source to the aeroplane unless a battery indicating a charge of at least 20 volts is fitted.
AC power inverters:
How many inverters are where are they located?
Fitted in the wing section, outboard of each nacelle
Starter Limitations?
40s on, 60s off
40s on, 60s off
40s on, 30min off
