Electrical Flashcards
To which BUS does external power connect?
MAIN 1
With exterenal power connected which BUSES are powered?
All - ESS, MAIN, NON-ESS
What are the main functions of the GCU’s?
- CONTROL
- MONITOR
- PROTECT
During starting what does the MAIN Battery do?
Feeds power to the starter generator
During engine starting what does the AUX Battery do?
Feeds the ESS BUSES during engine start up
Are MAIN and AUX Batteries recharged by the External Power Unit?
NO - they are automatically disconnected when external power is applied
What is the External Power used for?
- Supply power to all DC Bus Bars
2. Feed the starter during engine starting
What do the PDP’s do?
- Connect the Generators and Batteries to the LH and RH distribution bars via MAIN LOAD BUS 1 + MAIN LOAD BUS 2
- Check and connect the external power souce to the aircraft distribution Bus Bars 3. Control the BUS TIE Connector
BUS TIE Switch ON does?
BUS TIE connector closes = MAIN BUS 1 + MAIN BUS 2 are interconnected
BUS TIE Switch AUTO does?
BUS TIE contactor operates automatically, (Normal Position)
BUS TIE Switch RESET does?
Resets the latching protection logic that inhibits BUS TIE contactor operation (Spring Loaded Position)
GEN 1 Switch OFF does?
Disables or shuts down Generator 1 and resets latched functions in GCU 1
GEN 1 Switch ON does?
Requests GCU 1 to control Generator 1 to be on-line
GEN 2 Switch OFF does?
Disables or shuts down Generator 2 and resets latched functions in GCU 2
GEN 2 Switch ON does?
Requests GCU 2 to control Generator 2 to be on-line
BATTERY MASTER Switch OFF does?
Disconnects MAIN + AUX batteries from all BUS BARS
BATTERY MASTER Switch ON does?
Connects MAIN + AUX Batteries to the ESS BUSES, Enables the MAIN + AUX Battery Switches
MAIN BATT OFF switch does?
Disconnects MAIN Battery from MAIN BUS 1
MAIN BATT ON Switch does?
If Battery Master Switch is ON the connects MAIN Battery to MAIN BUS 1
AUX BATT Switch OFF does?
Disconnects the AUX battery from MAIN BUS 2
AUX BATT Switch ON does?
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’?
BELOW 22V
At what voltage to the electrical indicators show a value of zero?
BELOW 15V
When starting the second engine on batteries, IS the online generator allowed to operate in the Red Range overload condition?
YES
In the case of a MAU 1 or 2 failure what information must we NOT use?
SYNOPTIC PAGES INFORMATION
Before engine start - BATT MAIN on, MAIN + AUX BATT on, GEN 1+2 on…is MAIN BUS 2 powered?
NO
Before attempting to start the engine on batteries what ‘involved’ MAIN BUS voltage must be available?
NOT LESS than 23V
To start engine No2 what must we do with the BUS TIE switch?
Set to ON (to connect MAIN BUS 1 with MAIN BUS 2 to allow 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 and the other GEN = OFF-LINE
- EXTERNAL POWER connected to the helicopter BUS BARS
At what Ng is the start signal removed from the generator by the GCU?
Ng = 49% (detected by the EEC)
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 2. NON ESS BUS 1 and NON ESS BUS 2 are disconnected 3. MOMENTARY OVERCURRENT SITUATION
(DC BUS FAIL)…what happens?
- Drives the DC BUS FAIL message in the CAS
2. 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 to OFF - in order to 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
Bus Tie Switch Relay #
K10
Gen 1 Switch Relay #
K5
Gen 2 Switch Relay #
K6
Battery Master Switch Relay #
K1 & K2
Battery Main Switch Relay #
K3
Battery Aux Switch Relay #
K4
Ext Power Switch Relay #
K9
Inhibited Relays With External Power
K3, K4, K5, K6
