*
One or both condenser inlet temperature senors operate
*
ECV operates
*
Pack flow is less than the scheduled value or ambient temperature is less than 20F (-7C)
*
Conditions for ACM not failed -condenser bypass are true.
The conditions for ACM not failed -condenser bypass change with altitude. The chart shows five examples.
ACM NOT FAILED -CONDITIONS FOR CONDENSER BYPASS
ALTITUDE AMBIENT TEMP F (C) *[1]
三 0 三 14 (-10)
10,000 三 -9 (-23)
20,000 三 -18 (-28)
之 30,000 三 -24 (-31)
*[1] IF AMBIENT TEMP 三 INDICATED VALUE, THEN CONDENSER BYPASS CAN OCCUR.
In the economy cooling mode, air goes directly from the secondary heat exchanger to turbine two of the ACM. The CTC sets the second stage turbine bypass valve to control pack output temperature and the low limit valve to keep the condenser inlet above 34F (1C).
The CTC keeps a pack in the economy cooling mode until any one of these conditions is true:
* Conditions for condenser bypass are not true
EFFECTIVITY
BEJ ALL
*
TBV full closed, ram air doors more than 80 percent open and pack outlet temperature 5F (2.7C) more than IMMTE
*
Pack flow schedule 4 is active
*
Actual pack flow less than 100 ppm or more than two times the value of pack flow schedule 2.
There are no flight deck effect when the pack operates in the economy cooling mode.
Non-Normal Operations
In addition to compressor and pack outlet overheat conditions, these cause non-normal operations:
*
ACM failure
*
Pack temperature sensor failures
*
Economy cooling value failure
*
Low limit valve failure
*
Turbine bypass valve failure
*
Ram air door failures
*
Single pack operation.
Standby Cooling Mode
These faults cause the related pack to operate in the standby cooling mode:
*
ACM failure
*
Condenser inlet temperature sensors 1 and 2 fail
*
Economy cooling valve failed open.
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AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CTRL -FUNCTIONAL DESCRIPTION -PACKS
There are two ways the pack can operate when in the standby cooling mode: heat exchanger cooling or condenser bypass. The related CTC sets how the pack operates in the standby cooling mode based on which of these components have failed:
*
Heat exchanger cooling occurs if the ACM fails
*
Condenser bypass occurs if both condenser sensors, 1 and 2 fail or if the economy cooling valve fails in the open position.
These indications show when a pack operates in the standby cooling mode: the advisory message PACK MODE L (R) shows and the message STBY COOLING shows next to the related pack symbol on the air synoptic display.
See the air conditioning section for more information about the air synoptic display (SECTION 21-00).
ACM Failure (Heat Exchanger -STBY COOLING mode)
If an ACM failure occurs, the pack continues to operate in the STBY COOLING mode only if the ACM failed -condenser bypass criteria is met or when the other pack cannot meet the minimum flow necessary for schedule 4. If not, the pack stops. The pack can start again if the above conditions make it necessary.
The conditions for ACM failed -condenser bypass change with altitude. The chart shows five examples.
EFFECTIVITY
BEJ ALL
ACM FAILED -CONDITIONS FOR CONDENSER BYPASS
ALTITUDE AMBIENT TEMP F (C) *[1]
三 0 三 35 (2)
10,000 三 25 (-4)
20,000 三 18 (-8)
之 30,000 三 12 (-11)
*[1] IF AMBIENT TEMP 三 INDICATED VALUE, THEN CONDENSER BYPASS CAN OCCUR.
When the pack operates in the heat exchanger -STBY COOLING mode, the related CTC sets these valves fully open:
*
Economy cooling valve
*
Low limit valve
*
Turbine bypass valve.
In this mode, the CTC adjusts the position of the ram air doors to control the pack outlet air temperature, heat exchanger cooling only. If the pack can not hold the necessary temperature (pack out temperature 5F (2.7C) greater than IMMTE) and the TBV is not full open, the CTC sends a signal to the ASCPC for a lower precooler outlet temperature, (250F, 121C).
See the engine air supply section for more information about the precooler out temperature control and bleed air control (SECTION 36-11).
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AIR CONDITIONING -PACK CLG AND MIX MANIFOLD TEMP CTRL -FUNCTIONAL DESCRIPTION -PACKS
Condenser Sensor/Economy Cooling Valve Failure (Condenser Bypass -STBY COOLING mode)
If both condenser inlet temperature sensors 1 and 2 fail or if the economy cooling valve fails open, the pack continues to operate in the STBY COOLING mode only if the ACM not failed -condenser bypass criteria is met. If not, the pack stops. The pack can start again if the condenser bypass criteria is met. When the pack operates in the condenser bypass -STBY COOLING mode, the related CTC controls the pack outlet temperature with these pack components:
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