AC system Flashcards
What does the 115V variable frequency AC system supply power to?
TRUs
Electrical pumps (SPU and aux fuel)
Anti icing heaters for windshields, elevator horn, AoA vanes, Prop De-ice
How are the AC generators powered/mounted? When do the generators come online?
On the propeller Reduction gear box
Come online after engine start when props brought out of the feather position
Where is the AC GCU located?
AC contactor Box in the engine nacelle.
Why might the #1 AC GEN caution light illuminate in flight?
#1 generator output exceeded 125v causing it to shut down, #1 generator may have failed, #1 generator may have been switched off by pilot
is there a checklist for loss of both AC generators?
No, it’s unlikely this would happen. The QRH lists services that would be lost in the L and R AC buses.
When external AC power is connected, what buses are powered?
Both variable frequency AC buses, then power sent to all 28v DC buses through TRUs
Can external AC power be used to start the engines?
No, it can be used to set the aircraft up for an engine start, but not too start the engine.
Why must extreme caution be exercised before connecting external AC power to the aircraft?
Once applied, if either SPU switch on, the hydraulic system will be activated and gear doors will Snap closed.
What is the maximum AC loadmeter reading allowed on the ground if the temp is above 10 degrees Celsius?
0.33
What do the inverters do? What power and buses do they supply?
They invert 28v DC power to 115 400 hertz AC power to 2 buses. The fixed frequency 115v AC bus send power through a transformer to power the 26v AC buses.
What is a possible cause of all 3 inverter caution lights as well as both 26v AC caution lights being Illuminated?
A faulty paralleling control box or possibly one faulty inverter had caused the paralleling control box to take all inverters off line.
What are some things powered by the 26v AC buses?
ADF 1 and 2 ADI 1 and 2 HSI 1 and 2 ALT 1 and 2 HYD quantity ind and transfer RMI (powered by opposite bus) PFCS ind
