Purpose
The duct vent valve (DVV) releases air pressure from the engine duct when there is too much pressure in the duct. It prevents an overpressure condition if there is leakage through the HPSOV when the both HPSOV and PRSOV are closed. If the HPSOV is not fully closed, the flow out of the DVV is not sufficient to prevent an overpressure condition.
Location
The DVV attaches to the engine HP/IP manifold on the right side of the engine core near the 12:00 position. The valve is forward of the precooler adjacent to one of the fifteenth stage bleed air ports.
Physical Description
The DVV is a spring-loaded closed pressure relief valve. The valve is pneumatically actuated. The valve has a flow direction arrow on it.
Functional Description
The DVV opens when the pressure in the HP/IP manifold is more than 185 psig. The valve releases the air into the engine compartment at a flow of 6 to 8 lbs/min (2.72 to 3.63 kg/min). The valve resets at 145 psig.
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ENGINE AIR SUPPLY SYSTEM -DUCT VENT VALVE
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ENGINE AIR SUPPLY SYSTEM -AIR SUPPLY CABIN PRESSURE CONTROLLER -PHYSICAL DESCRIPTION
Location
The left and right air supply cabin pressure controllers (ASCPC) are in the MEC on the E1 and E2 racks.
Physical Description
The ASCPCs have test and cabin pressure sense ports on the front. The test port is for in-shop service. The cabin pressure sense port lets the controllers monitor cabin pressure.
The ASCPCs use operational program software (OPS) that you can load.
Training Information Point
The ASCPCs are LRUs. The circuit cards inside the ASCPC are not LRUs.
The left and right ASCPCs are interchangeable.
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ENGINE AIR SUPPLY SYSTEM -AIR SUPPLY CABIN PRESSURE CONTROLLER -PHYSICAL DESCRIPTION
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ENGINE AIR SUPPLY SYSTEM -AIR SUPPLY CABIN PRESSURE CONTROLLER -PURPOSE
Purpose
The left and right air supply cabin pressure controllers (ASCPC) give control for these systems:
*
Pneumatic (engine air supply and air supply distribution)
*
Pressurization
*
Air conditioning (pack flow schedule and backup pack control).
The controllers also give indications, have BITE, and have interfaces with other airplane systems to give engine bleed air flow management. See the engine bleed air flow management page in this section for more information about flow management.
Control Modes
The ASCPCs have two modes: digital and analog. The ASCPCs use the digital control mode for these systems:
*
Engine air supply
*
Air supply distribution
*
Pressurization
*
Pack flow schedule
*
Backup pack flow control.
The ASCPCs use analog control mode as a backup to digital mode for the engine air supply system.
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The digital mode of the ASCPCs controls in any one of three ways:
*
At the same time
*
Primary
*
Backup control.
These are the systems controlled by the ASCPCs:
SYSTEM ASCPC CONTROL
L ENGINE AIR SUPPLY L PRIMARY
R ENGINE AIR SUPPLY R PRIMARY
AIR SUPPLY DISTRIBUTION L & R SAME TIME
PRESSURIZATION & PACK FLOW SCHEDULE L PRIMARY
PRESSURIZATION & PACK FLOW SCHEDULE R BACKUP
L PACK FLOW CONTROL L BACKUP TO L CTC
R PACK FLOW CONTROL R BACKUP TO R CTC
For the systems listed in the above table, the digital control mode supplies these functions:
*
Control
*
Indication
*
Protection
*
BITE.
For the engine air supply system, the analog control mode gives these functions:
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ENGINE AIR SUPPLY SYSTEM -AIR SUPPLY CABIN PRESSURE CONTROLLER -PURPOSE
*
ON/OFF control through the engine bleed air switch (PRSOV only)
*
OFF indications
*
Temperature limiting through the PRSOV
*
Overheat protection
