*
F/D or MEC duct air flow is low.
In the air, both the low flow indication signal (5 minute delay) and low flow override mode signal (60 second delay) are sent if all of these conditions occur:
*
F/D air flow is low or the F/D sensor circuit has a malfunction
*
MEC air flow is low or the MEC sensor circuit has a malfunction.
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A/C -EQUIPMENT COOLING -FUNCTIONAL DESCRIPTION -LOW FLOW SENSORS
Flight Deck Indication
The low flow indication signal causes the EQUIP COOLING advisory message. The advisory message is inhibited in the air.
If a sensor fails, status messages show to tell you which sensor has a malfunction.
Ground Crew Call Horn
The ground crew call horn operates if the airplane is on the ground and any one of these conditions occur:
*
Low flow -indication
*
ADIRU on battery power
*
Ground crew call selected (center CDU or flight deck hand set).
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EFFECTIVITY BEJ ALL 21-27-00
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A/C -EQUIPMENT COOLING -FUNCTIONAL DESCRIPTION -OVERRIDE MODE
General
The ECSMCs control the override (OVRD) mode. The card in control puts the forward equipment cooling system into the override mode. The override mode occurs if any of these conditions occur:
*
The left and right supply fans failed off and the airspeed is more than 150 knots
*
LOW FLOW -OVRD MODE signal when the airspeed is more than 150 knots
*
Smoke alarm from the equipment cooling smoke detector
*
Forward cargo fire switch in the ARMED position
*
Equipment cooling switch in the OVRD position.
Supply Fans Malfunction
The ECSMC in control latches the system to the override mode if the airspeed is more than 150 knots and the two supply fans are off because of a malfunction.
For more information on the supply fans, see the functional description of the supply fans in this section.
Low Air Flow
The ECSMCs use special logic to find a low air flow condition. See the section on the low flow sensors for more information. If a LOW FLOW -OVRD MODE signal occurs and the airspeed is more than 150 knots, the ECSMC in control latches the system to the override mode.
EFFECTIVITY
BEJ ALL
Smoke Alarm
The ECSMC in control latches the system to the override mode if it gets a smoke alarm signal from the equipment cooling smoke detector.
Reset
The latch caused by the failure of both supply fans or the LOW FLOW -OVRD MODE signal or a smoke alarm resets if the condition that caused it goes away and any of these conditions occur:
*
Airspeed is less than 70 knots
*
Nose gear compressed (PSEU 2)
*
Power cycled off then to on
*
Forward cargo fire switch in the ARMED position
*
Equipment cooling switch in the out position.
Forward Cargo Fire Switch Set to ARMED
The ECSMC in control puts the system into the override mode when the forward cargo fire switch is in the ARMED position. The system stays in this mode as long as the switch is set to ARMED.
Equipment Cooling Switch to Out
The ECSMC in control puts the system into the override mode when the equipment cooling switch is set to the out position. The system stays in this mode as long as the switch is in the out position.
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A/C -EQUIPMENT COOLING -FUNCTIONAL DESCRIPTION -OVERRIDE MODE
Override Mode
The override mode causes the forward part of the equipment cooling system to make these changes:
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