AW139 PTS - Electrical Flashcards
Describe the electrical system
28V DC powered by 2 starter generators (30V, 300A DC Gens)
24V NiCad Main Battery (for start and emergency)
24V Aux Batt (Feeds essentials during start and emergency)
What generates electrical power?
Two 30V, 300A DC air cooled starter-generators
What is the aircraft voltage?
28V DC
How many batteries does the electrical system have?
2 24V NiCad batteries
Main and Aux
How many bus bars are there?
6
Essential 1 & 2
Main 1 & 2
Non-Essential 1 & 2
What electrical indications are on the MFD?
Main & Ess Bus 1&2 Voltage
Gen load (%)
Main and Ess Batt ampere-meters condition
How do we know which cct breaker is tied to which bus?
Essential = 1 rectangle Main = 2 rectangles Non-Ess = no rectangles
How does the BUS TIE work and what is the logic during a GEN failure?
ON - MAIN 1 & 2 are connected
AUTO - Normally open (disconnected). If system detects a GEN fail - it closes to power both sides.
If it detects a short circuit, it latches OPEN.
RESET - Resets latching protection after overcurrent detected (can be disappointing if you get this wrong)
What controls and monitors the Generators
GCUs
What happens if you have a short circuit on MAIN bus 1 during flight?
- GCU senses too much power being drawn from the bus
- Shuts down Gen 1 and inhibits bus tie
- Loss of MAIN 1 and both Non Ess busses
How much time do you have after a dual gen fail?
30 mins
17 with Main Bat on
How can we extend power during a dual gen failure?
- Turn OFF: Main battery, fuel crossfeed, fuel pumps, pilot MFD, unnecessary lights, pitot heat
(USE QRH!!!)
If a good external power source is connected and nothing happens what can you check?
The circuit breaker in the external power receptacle bay
Can we disconnect the Aux battery after shutdown?
YES
Open nose cowl and unscrew (after 5 mins)
What do we do if a [BATT HOT] CAS appears?
Turn the associated batt off.
And realise that you have lost if in the event of a double gen fail
