(2)
When no air is in the system, the spring keeps the flapper plate closed. When the air flows from the air cooling pack to the mix manifold, it pushes the flapper plate open. The air cannot flow in the opposite direction because the flapper plate can only move in the one direction. Thus, the check valve prevents the flow of air from the mix manifold to the air cooling pack.
T. Flow Control Card (Fig. 11A)_________________
(1) The flow control card is in the P50 card file in the main equipment bay. The card controls the position of the flow-control-and-shutoff valve. It also controls the indications that show when an overheat condition occurs.
CARD FILE CARD
GUIDE DOOR
DOOR FASTENER (TYP)
P50 CARD FILE ASEE
P50 CARD FILE FLOW CONTROL CARD CONNECTOR ELECTRICAL (TYP) EJECTOR
A
Figure 11A Flow Control Card
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757
MAINTENANCE MANUAL
3. Operation
_________
A. Functional Description (Fig. 11B, 12)
______________________
(1)
The cooling pack system puts out a specified amount of air at a specified temperature. The Functional Description of the cooling pack system is divided into three parts:
(a)
The Air Cooling Pack Operation tells what happens to the air as it flows through the air cooling pack.
(b)
The Pack Flow Control tells how the cooling pack system gets the necessary amount of air from the air cooling pack.
(c)
The Pack Temperature Control tells how the cooling pack system gets the necessary air temperature from the air cooling pack.
(2)
The Air Cooling Pack Operation (Fig. 12)
(a)
The air cooling pack is pneumatically operated. It operates only when a supply of air goes into it. The flow-control-and-shutoff valve lets air enter the air cooling pack. Thus, when the flow-control-and-shutoff valve is open, the air cooling pack is ON. When the flow-control-and-shutoff valve is closed, the air cooling pack is OFF.
(b)
Air from the flow-control-and-shutoff valve first flows into the primary heat exchanger. The primary heat exchanger causes the air temperature to decrease. Then the pressure and the temperature of the air is increased as it flows through the air-cycle-machine compressor. The secondary heat exchanger again causes the air temperature to decrease.
(c)
Then the water is removed from the air. The split-duct water-separator removes an initial amount of water as the air moves from the secondary heat exchanger. Then the air flows through the reheater and the condensor, which both cause the air temperature to decrease. The low temperature of the air causes water drops. Subsequently, as the air flows through the water extractor, the water extractor removes the water. The water extractor puts the water in the ram air system or lets it flow overboard.
(d)
After the water is removed from the air, the air flows the other direction through the reheater. This causes the temperature to increase before it goes into the air-cycle-machine turbine.
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757
MAINTENANCE MANUAL
PACK
STBY
CONT
ZONE TRIM AIR
ZONE TRIM ZONE TRIM
AIR CHECK AIR CHECK
VALVE VALVE
RAM AIR
INLET DOOR
RIGHT PACKTEMPCONTROLLER(SAME PACK
SIGNALS ALTITUDE WATER SPRAY LINE
AS LEFT SWITCH
SIDE)
SPLIT-DUCT MIX WATER MANIFOLD
TO FWDPASSENGER
SEPARATOR TEMP
ZONESENSOR 2
SECONDARY
HEAT TO AFTEXCHANGER TO FLIGHT
PASSENGERCOMP OUTLET
COMP OUTLET DECK ZONE
ZONE SENSOR 2
SENSOR 1 PACK TEMP
COMP
PRIMARY SENSOR 2
OVHT SW
HEAT
EXCHANGER
MIXMANIFOLDTEMP
REHEATERBLEED AIR
RAM AIR SENSOR 1 FROM R ENGINE/
DEICING LINE APU/
EXHAUST
DOOR SAME AS GROUND SOURCE
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