IN FLIGHT EMERGENCIES AND MALFUNCTIONS
In the following pages the most significant emergencies and malfunctions
are detailed using the simplified schematic diagram (F1 to F5). Refer to
AW139-RFM-4D – Section 3 for Emergency and Malfunction procedures.
F1 – SINGLE GENERATOR FAILURE (1 DC GEN)
When a GCU detects that the relevant Generator has failed, it automatically
opens the Generator contactor.
The same CAS message is displayed when the GEN switch is moved to
OFF while the relevant engine is running.
• BUS TIE contactor automatically closes
• NON ESS BUS 1 and NON ESS BUS 2 are disconnected
F2 – MOMENTARY OVERCURRENT CONDITION (DC BUS FAIL)
When a GCU detects an overcurrent exceeding a first threshold (OC1), it
triggers a latching logic that:
• Drives the DC BUS FAIL message in the CAS
• Inhibits the BUS TIE contactor automatic operation (remains open)
Once triggered, the OC latching logic can only be reset by moving the BUS
TIE switch to RESET.
F3 – SHORT CIRCUIT (DC BUS FAIL + 1 DC GEN)
If the overcurrent condition persists, a second threshold is then exceeded
(OC2): that is considered a short circuit.
In this case the relevant GCU also:
• disconnects the relevant Generator, causing the 1 DC GEN or the 2
DC GEN message to be displayed
• disconnects the relevant Battery to prevent it from discharging on the
short circuit, causing the MAIN BATT OFF or the AUX BATT OFF
message to be displayed
BUS TIE contactor remains open to prevent the failed bus from being
connected to the only available generator.
NOTE
Pilot must do nothing.
F4, F5, F6 – DUAL GENERATOR FAILURE (1 2 DC GEN)
When both Generators have failed, the 1-2 GEN warning message is
displayed in the CAS and only MAIN and AUX Batteries supply the aircraft
loads. Manual shedding of the MAIN BUS 1 (BATTERY MAIN switch to
OFF) is required in order to only supply the Essential (Emergency) loads.
NOTE
Following a dual generator failure land within the time limit stated in
the RFM or QRH. If batteries discharge completely (electrical black
out) the engines continue to run in AUTO Mode: they are controlled
by the EEC which is electrically powered by the relevant Permanent
Magnet Alternator (PMA). Since the landing gear is electrically
controlled for both normal and emergency operation (see ch. 32-00),
it is necessary to extend it before losing electrical power completely;
an increase in fuel consumption is then to be expected.
IN FLIGHT EMERGENCIES AND MALFUNCTIONSIn the following pages the most significant emergencies and malfunctionsare detailed using the simplified schematic diagram (F1 to F5). Refer toAW139-RFM-4D – Section 3 for Emergency and Malfunction procedures.F1 – SINGLE GENERATOR FAILURE (1 DC GEN)When a GCU detects that the relevant Generator has failed, it automaticallyopens the Generator contactor.The same CAS message is displayed when the GEN switch is moved toOFF while the relevant engine is running.• BUS TIE contactor automatically closes• NON ESS BUS 1 and NON ESS BUS 2 are disconnectedF2 – MOMENTARY OVERCURRENT CONDITION (DC BUS FAIL)When a GCU detects an overcurrent exceeding a first threshold (OC1), ittriggers a latching logic that:• Drives the DC BUS FAIL message in the CAS• Inhibits the BUS TIE contactor automatic operation (remains open)Once triggered, the OC latching logic can only be reset by moving the BUSTIE switch to RESET.F3 – SHORT CIRCUIT (DC BUS FAIL + 1 DC GEN)If the overcurrent condition persists, a second threshold is then exceeded(OC2): that is considered a short circuit.In this case the relevant GCU also:• disconnects the relevant Generator, causing the 1 DC GEN or the 2DC GEN message to be displayed• disconnects the relevant Battery to prevent it from discharging on theshort circuit, causing the MAIN BATT OFF or the AUX BATT OFFmessage to be displayedBUS TIE contactor remains open to prevent the failed bus from beingconnected to the only available generator.NOTEPilot must do nothing.F4, F5, F6 – DUAL GENERATOR FAILURE (1 2 DC GEN)When both Generators have failed, the 1-2 GEN warning message isdisplayed in the CAS and only MAIN and AUX Batteries supply the aircraftloads. Manual shedding of the MAIN BUS 1 (BATTERY MAIN switch toOFF) is required in order to only supply the Essential (Emergency) loads.NOTEFollowing a dual generator failure land within the time limit stated inthe RFM or QRH. If batteries discharge completely (electrical blackout) the engines continue to run in AUTO Mode: they are controlledby the EEC which is electrically powered by the relevant PermanentMagnet Alternator (PMA). Since the landing gear is electricallycontrolled for both normal and emergency operation (see ch. 32-00),it is necessary to extend it before losing electrical power completely;an increase in fuel consumption is then to be expected.
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