AIR SUPPLY DISTRIBUTION -FUNCTIONAL DESCRIPTION -APU SHUTOFF VALVE CONTROL LOGIC
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AIR SUPPLY DISTRIBUTION -FUNCTIONAL DESCRIPTION -SUMMARY -NORMAL CONDITIONS
Functional Description
The ASCPC controls the air supply distribution system. It controls the position of these valves:
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Left isolation valve
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Center isolation valve
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Right isolation valve
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APU shutoff valve
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Left PRSOV
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Right PRSOV.
The table shows different configurations of the valves for normal conditions.
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AIR SUPPLY DISTRIBUTION -FUNCTIONAL DESCRIPTION -SUMMARY -NORMAL CONDITIONS
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AIR SUPPLY DISTRIBUTION -FUNCTIONAL DESCRIPTION -SUMMARY -NON-NORMAL CONDITIONS
General
The ASCPCs monitor for non-normal conditions that effect the distribution of the air to the ADPs and other air user systems. The ADPs are most important. If a non-normal condition occurs, the ASCPCs limit the effect, by isolating parts of the pneumatic distribution system.
The table shows the different configurations of the isolation, APU shutoff, and the pressure regulating and shutoff valves for non-normal conditions.
Source Loss Condition
The source loss condition logic lets the ASCPCs sense when there is not sufficient air pressure to the ADPs for landing gear retraction immediately after takeoff.
There are two sets of conditions that cause the source loss condition. One set is true if all of these conditions occur:
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Landing gear down
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Less than 180 seconds since takeoff
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Left engine off.
The second set is true if all of these conditions occur:
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Landing gear down
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Less than 180 seconds since takeoff
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left duct pressure less than 20 psig and right duct pressure more than 20 psig.
EFFECTIVITY
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Bleed Pressure Loss Condition
The bleed pressure loss condition logic lets the ASCPCs sense when a pneumatic duct comes apart. Possible engine starter duct failure is the primary reason for this logic.
There are two sets of conditions that cause the ASCPCs to set the left bleed pressure loss condition to true. One set is true if all of these conditions occur for more than 10 seconds:
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Left duct pressure is less than 13 psig
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Left pack inlet pressure is less than 13 psig
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Right duct pressure is more that 13 psig
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Left PRSOV is open
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Right PRSOV is open
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No duct leak signal from the duct leak and overheat detection system (DLODS)
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Landing gear is up
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Takeoff less than 180 seconds.
The second set is true if all of these conditions occur for more than 10 seconds:
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Left duct pressure is less than 13 psig
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Left pack inlet pressure is less than 13 psig
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Right PRSOV is open
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Left PRSOV is closed
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Landing gear is up or (takeoff more than 180 seconds)
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Left engine bleed air flow is more than 2.0 lbs/sec
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No left engine start.
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AIR SUPPLY DISTRIBUTION -FUNCTIONAL DESCRIPTION -SUMMARY -NON-NORMAL CONDITIONS
Bleed Leak Conditions
Ducts in the pneumatic distribution system are monitored by the duct leak and overheat detection system (DLODS) for air leaks that cause an overheat condition. The DLODS provides the ASCPCs this general location information:
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Bleed leak in the strut area L (R)
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Bleed leak in the wing area L (R)
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Bleed leak in the body area.
The DLODS can not tell the ASCPCs the duct that caused the overheat. One overheat condition can be caused by different ducts. This is an example. An overheat in the left pack area can be caused by a duct that connects any of these components:
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L PRSOV to L Pack and L ISLN valve
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