AW 139 Electrical Flashcards
Electrical System
28VDC
Electrical System Purpose
Generate and distribute DC elec pwr
Store energy (Batts)
In-flight emergency ops
Autonomous engine start and gnd ops
Distribute DC elec pwr from an external ground pwr source
Electrical System Components
2X Starter-Gens w/Gen Control Unit (GCU)
MAIN Battery
AUX Battery
ESS BUS
MAIN BUS
NON ESS BUS
Main Battery
Feed pwr during Eng Start
Feed Ess + Main loads during
In-flight emergency (dual Gen Fail)
On gnd (eng - off + Ext Pwr- off)
AUX Battery
Feed pwr to the Ess loads during
Eng Start
In-flight emergency
On gnd (eng - off + Ext Pwr- off)
ESS BUS
Connected via CB w/diode protection to prevent feeding its counterpart
MAIN BUS
Normally isolated / can be connected via BUS TIE due to GEN FAIL or inop
Function of Generator Control Unit’s (GCU’s)?
CONTROL, MONITOR, PROTECT gens
Function of Power Distribution Panel’s (PDP’s)?
Connect the Gens and Batts to the LH and RH distro bars via MAIN LOAD BUS 1 + MAIN LOAD BUS 2
Check and connect EXT PWR source to bus bars
Control BUS TIE Contactor
With external power connected which BUSES are powered?
All - ESS, MAIN, NON ESS
To which BUS does external power connect?
MAIN 1
During engine start what does the MAIN Battery do?
Feed power to the starter generator
During engine start what does the AUX Battery do?
Provides stable voltage to the ESS BUSES
Are MAIN and AUX Batteries recharged by the External Power Unit?
NO - Automatically disconnected when EXT PWR is applied
What is the External Power used for?
Supply power to all DC Bus Bars
Feed the starter during engine start
BUS TIE - ON?
BUS TIE connector closes = MAIN BUS 1 + MAIN BUS 2 interconnected
BUS TIE - AUTO?
BUS TIE contactor operates automatically (Normal Position)
BUS TIE - RESET?
Resets latching protection logic that inhibits BUS TIE contactor operation (Spring Loaded Position)
GEN 1 - OFF?
Disables or shuts down Generator 1 and resets latched functions in GCU 1
GEN 1 - ON?
Requests GCU 1 to control Generator 1 to be on-line
GEN 2 - OFF?
Disables or shuts down Generator 2 and resets latched functions in GCU 2
GEN 2 - ON?
Requests GCU 2 to control Generator 2 to be on-line
BATTERY MASTER - OFF?
Disconnects (MAIN + AUX) Batts from all BUS BARS
BATTERY MASTER - ON?
Connects (MAIN + AUX) Batts to the ESS BUSES
Enables (MAIN + AUX) Batt Switches
MAIN BATT - OFF?
Disconnects MAIN Batt from MAIN BUS 1
MAIN BATT - ON?
If Battery Master Switch is ON the connects MAIN Battery to MAIN BUS 1
AUX BATT - OFF?
Disconnects the AUX battery from MAIN BUS 2
AUX BATT - ON?
If Battery Master ON then connects AUX Battery to MAIN BUS 2
Red Gang Bar moved BACKWARD does?
Cuts off all aircraft electrical power sources at same time
GEN 1, GEN 2, BATTERY MASTER
At what voltage do the electrical indicators display in ‘amber reverse video’?
< 22V
At what voltage to the electrical indicators show a value of zero?
< 15V
When starting the second engine on batteries, IS the online generator allowed to operate in the Red Range overload condition?
YES (45 secs)
In the case of a MAU 1 or 2 FAIL, what information must we NOT use?
SYNOPTIC PAGES INFORMATION
Starter/Generator
Brush Type / Force air cooled
Before Eng Start - BATT MAIN on, MAIN + AUX BATT on, GEN 1 + 2 on - is MAIN BUS 2 powered?
NO - To conserve Batt Pwr
Before attempting Eng Start (Battery) what must the ‘involved’ MAIN BUS voltage be?
NOT LESS than 23V
Before attempting Eng Start (EXT PWR) what must the ‘involved’ MAIN BUS voltage be?
NOT LESS than 23V
Batteries discharging
**Both ensure pwr to ESS BUSES
What position is the BUS TIE switch for second Eng Start?
ON (Connects MAIN BUS 1 with MAIN BUS 2 allowing power to flow to the MAIN BUS 2 for GEN 2 to work)
The BUS TIE connector closes with what three conditions?
BUS TIE Switch - ON
One Gen = ON-LINE + One Gen = OFF-LINE
EXTERNAL POWER - ON
At what Ng is the start signal removed from the generator by the GCU?
Ng = 49% (detected by the EEC)
At what Ng does the GCU close the Gen connection?
Ng = 50%
When the generator moves from starter mode to generator mode, what Nf does the EEC accelerate the engine to?
Nf = 65% (IDLE)
- or -
Nf = 100% (FLIGHT)
During engine start, what is providing the power for the DU’s so that the pilots can monitor the engine parameters?
The AUX BATTERY via the ESS BUSES
SINGLE GENERATOR FAILURE (1 DC GEN) - What happens?
BUS TIE contactor automatically closes
NON ESS BUS 1 and NON ESS BUS 2 are disconnected
MOMENTARY OVERCURRENT SITUATION
DC BUS FAIL - What happens?
Drives the DC BUS FAIL message in the CAS
Inhibits the BUS TIE contactor automatic operation (remains open)
SHORT CIRCUIT (DC BUS FAIL + 1 DC GEN) - What happens?
Disconnects relevant generator (thus displaying 1(2) DC GEN message)
Disconnects relevant battery (causing MAIN BATT OFF or AUX BATT OFF to be displayed)
BUS TIE contactor remains OPEN
PILOT MUST DO NOTHING
DUAL GENERATOR FAILURE (1-2 DC GEN) - What happens?
Only MAIN and AUX batteries supplying the loads.
Hence MAIN BATT switch - OFF (IOT supply ONLY the ESSENTIAL loads (ie emergency loads))
ELECTRICAL BLACKOUT - What happens?
If batteries totally discharged - engines continue to run in AUTO Mode (controlled by EEC - which is powered by the relevant PMA (Permanent Magnetic Alternator))
What does MAIN BATT OFFLINE caution message mean?
One of the two batteries is not connected to the ESS BUS
What does MAIN BATT OFF caution message mean?
The MAIN battery is not connected to the MAIN BUS 1
What does AUX BATT OFF caution message mean?
The AUX Battery is not connected to MAIN BUS 2
When starting engine No.2 as the first engine with the external power not available, what is the position of the Bus Tie Switch?
ON
What is the minimum on-side Main Bus voltage required prior to starting the engines?
23 Volts
When starting an engine using the helicopter batteries what are the primary functions of the batteries?
The Main Battery power is used to start the engine while the Auxiliary Battery is only used to feed the Essential bus bars
The helicopter is on the ground with both engines running, the external power source is connected (EXT PWR switch = ON) and both generators are operating ( GEN 1 and GEN 2 switchs = ON ). From where are the electrical bus-bars fed?
The external power source, only
When the BATTERY MASTER, the MAIN BATTERY and the AUX BATTERY switches are set to ON and the external power unavailable
The MAIN BATT is used to start the engine no.1 while the AUX BATTERY is used to feed the essential bus-bars
When the two generators are operating ( GEN 1-2=ON ) while the A/C on ground and the external power still connected ( EXT.SX=ON )
The electrical bus-bars are fed by the external power
With the external power not available, the engine no.2 starting is performed
With the BUS TIE switch set to on
If the DC GENERATORS 1 LOADMETER parameter is declared invalid
The relative generator pointer is removed from view and the digital readout dashed
In case of generator failure
The NON ESS BUS 1 and 2 are automatically OFF
With the external power connected to the A/C, circle the correct condition
The ESS BUS 1 And 2, the MAIN BUS 1 and 2, the NON ESS BUS 1 and 2 are powered, the MAIN BATT and AUX BATT are OFF
When starting eng 2 as the first engine with the external power not available what is the position of the bus tie switch?
ON
