The ram-air system supplies atmospheric air to the dual heat exchanger (DHX) and pre-cooler.

Note:
The DHX is a component of the air conditioning system (pack) and the pre-cooler. is a component of the filtering and flow control system.

The ram-air system is also used as follows:

• As an auxiliary source of air supply to the cabin and to the flight compartment when there is no aircraft pressurization
• As part of the aircraft smoke evacuation procedures
• Usually, for all unpressurized flights

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The water sprayer is in the aft equipment compartment in the ram-air intake lower-duct.

Operation of the water sprayer is as follows:

• Water collected by the water extractor is sent to the water sprayer through the water separator tube
• Water in the water sprayer is released as a spray into the ram-air intake lower duct

Note:
The water extractor is a component of the pack.

The spray of water released into the ram-air intake lower duct decreases the temperature of the ram air upstream of the dual heat exchanger. This increases the performance of the pack.

Installation of the water sprayer is such that its water spray goes in the opposite direction of the ram airflow (counter flow). This configuration gives better distribution of the water in the ram-air intake lower duct.

The water sprayer can be divided into the three following components:

• The pipe, made out of aluminum alloy
• The nozzle, made out of brass. The nozzle releases the water into the ram airflow with a high speed circular movement
• The end fitting, made out of aluminum alloy

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The water separator tube is in the aft equipment compartment. It connects the water extractor to the water sprayer.

The water separator tube lets water flow from the water extractor to the water sprayer. The tube is made out of aluminum alloy.

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The ram-air regulating-valve is found in the aft equipment compartment, between the pack and the pre-cooler inlet header. Its function is to modulate ram airflow to control the temperature of the bleed air that comes out of the pre-cooler air outlets. This improves temperature control of the pack and the temperature control system. It also makes possible the use of light alloy material for the pack.

Note:
The pre-cooler has two air outlets. One of the outlets supplies bleed air to the pack. The other outlet supplies bleed air to the temperature control system. The pre-cooler is a component of the filtering and flow control system.

The ram-air regulating valve is not the only item that controls the temperature of the bleed air that comes out of the pre-cooler air outlets. Temperature of the bleed air at the pre-cooler air outlets is also related to the design of the pre-cooler itself and to the position of the flow control valves (FCVs). Together, the design of the pre-cooler position of the ram-air regulating valve, and position of the FCV limit the temperature of the bleed air at the pre-cooler air outlets to a maximum of 430°F (221°C).

Note:
The FCV are components of the filtering and flow control system.

The ram-air regulating-valve is an aluminum alloy body, 6 in. (15.24 cm) diameter valve. Internally, It has a 4.75 in. (12.07 cm) diameter butterfly-valve. The diameter of the butterfly valve is much smaller than the diameter of the ram-air regulating-valve body. Thus, the ram air that flows from the pack to the pre-cooler inlet header can not be fully stopped. When the ram-air regulating-valve is commanded to the full closed position, only approximately half of the quantity of ram airflow can be stopped. Such design makes the most out of the pack and prevents potential air cycle machine (ACM) fan surge conditions.

Note:
The ACM is a component of the pack.

The position of the butterfly valve is controlled by a 28 VDC electrical actuator itself controlled by IAS controller No. 2. IAS controller No. 2 can control the actuator from its channel A or B. Usually, channel A controls the actuator, but if channel A becomes unserviceable, control of the actuator comes from channel B.

The quantity of opening of the butterfly valve is related to the measurements that are made by the following sensors:

• Pack inlet temperature sensor (PITS) found at the inlet of the pack
• Hot-air temperature sensor (HATS) found at the inlet of the temperature control system

Note:
The PITS and HATS are components of the temperature control and indication system.

The ram-air regulating valve fully closed and fully open positions are sensed by end of travel micros-witches. The data from the end of travel micros-witches. goes to IAS controller No. 2. The maximum time for the valve to open is 4 seconds. The maximum time for the valve to close is 6 seconds.

The ram-air regulating-valve has an external lever through which the butterfly valve can be moved manually to 3 pre-defined positions. These positions are open, dispatch, and closed.

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The ram air duct is found in the aft equipment compartment. It connects the ram-air intake upper-duct to the ram air valve. Its function is to let ram air into the pack discharge duct when the ram air valve is opened.

Note:
The pack discharge duct is a component of the air-conditioning system. It supplies conditioned air or ram air to the cabin and to the flight compartment.

The ram air duct is made out of three layers of Kevlar phenolic resin component and has an internal layer of erosion, anti-static, aerodur finish (aerodur is a special type of finish). At one end, it has a bonded-on machined flange that mates with the ram air valve. At the other end, connection to the ram-air intake upper-duct is made with the hardware that follows:

• Silicon sleeve made stronger with fiberglass
• Clamps

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The ram-air intake upper-duct is found in the aft equipment compartment. It is connected to the ram air duct and to the ram-air intake lower-duct. Its function is to collects fresh air from the outside of the aircraft and to send it to the ram air duct and to the ram-air intake lower-duct.

The ram-air intake upper-duct is made out of several layers of Kevlar phenolic resin component and has an internal layer of erosion, anti-static, aerodur finish (aerodur is a special type of finish). It is attached to the ram air fairing with eight screws. It is also attached to the aircraft structure with two screws that go through the flanges that are part of the duct. Connection to the ram air duct and to the ram-air intake lower-duct is made with the hardware that follows:

• Silicon sleeves made stronger with fiberglass
• Clamps

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The ram-air intake lower duct is in the aft equipment compartment. It is connected to the ram-air intake upper duct and to the DHX. It lets ram air into the DHX. The water sprayer in it lets water into the ram airflow to better the performance of the pack.

The ram-air intake lower-duct is made out of several layers of Kevlar phenolic resin component and has an internal layer of erosion, anti-static, aerodur finish (aerodur is a special type of finish). It is attached to the DHX with bolts. It is also attached to the ram-air intake upper-duct with the hardware that follows:

• Silicon sleeve made stronger with fiberglass
• Clamps

The ram-air intake lower duct has a boss that hosts the water sprayer.

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The ram-air outlet duct (RAOD) is found in the aft equipment compartment. It is connected to the pre-cooler outlet header at one end, and attached to the aircraft structure at the other end. Its function is to send the ram air that comes out of the pre-cooler outlet header overboard.

The RAOD is a double skin, louvered outlet. It is designed to operate as a jet pump and makes sure that air in the aft equipment compartment is dragged along by the ram air sent overboard. The RAOD is attached to the aircraft structure with rivets.

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The ram air valve is found in the aft equipment compartment. It is connected to the ram air duct at one end, and to the pack discharge duct at the other end. When it is opened, the function of the ram air valve is to let ram air into the pack discharge duct. From the pack discharge duct, ram air then goes to the cabin and to the flight compartment.

The ram air valve is a 4 in. (10.16 cm) diameter valve with an aluminum alloy body and butterfly valve. It is operated by a 28 VDC actuator controlled from the AIR COND/BLEED control panel (through the RAM AIR push button annunciator (PBA)).

It takes a maximum of 4 seconds for the valve to open and a maximum of 6 seconds for the valve to close. The ram air valve full open and full closed positions are monitored by end of travel micros-witches. The data from the micros-witches. is sent to the DCU.

The ram air valve has an external lever to manually move and lock the butterfly valve in the full open or full closed position.

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In flight, forward movement of the aircraft pushes outside air into the scoop of the ram-air intake upper duct. That outside air (forced into the ram-air intake upper duct) is called ram air.

The ram air collected by the ram-air intake upper duct then goes to the following objects:

• To the DHX and pre-cooler
• If applicable, to the cabin and flight compartment

For the DHX and the pre-cooler the path of the ram airflow is as follows:

• Ram air goes to the DHX from the ram-air intake lower-duct. While the ram air passes through the ram-air intake lower-duct, water is sprayed into the airflow by the water sprayer. This betters the performance of the pack.
• When the ram air goes through the DHX, it cools, by convection, the bleed air used to make the aircraft's air conditioning.
• When it goes out of the pack (through the pack's plenum outlet), the ram air then goes to the pre-cooler through the ram-air regulating-valve and the pre-cooler inlet header. The ram-air regulating-valve modulates the ram airflow to control the pre-cooler outlets temperatures. The pre-cooler inlet header is an interface between the ram-air regulating-valve and the pre-cooler.

Note:
The ram-air regulating valve is not the only item that controls temperature of the bleed air that comes out of the pre-cooler air outlets. Temperature of the bleed air at the pre-cooler air outlets is also related to the design of the pre-cooler itself and the position of the flow control valves (FCVs). Together, the design of the pre-cooler position of the ram-air regulating valve, and position of the FCV limit the temperature of the bleed air at the pre-cooler air outlets to a maximum of 430°F (221°C).

• When ram air goes through the pre-cooler it decreases the bleed-air temperature to levels that are satisfactory for operation of the air conditioning system. It also decreases the bleed air temperature that supplies the temperature control system.
• After it has gone through the pre-cooler the ram air is sent overboard through the pre-cooler outlet header and the ram-air outlet duct.

Ram air can also supply the aircraft cabin and flight compartment. To do so, the RAM AIR PBA on the AIR COND/BLEED control panel must be pushed. This causes the ram-air valve to open. When the ram-air valve is opened, ram air goes to the cabin and flight compartment through a series of ducts.

Note:
When the RAM AIR PBA is pushed, the PBA lamp comes on.

Usually, the decision to let ram air supply the aircraft cabin and the flight compartment is made when there is a loss of aircraft pressurization. Ram-air also supplies cabin and flight compartment air as part of the aircraft smoke evacuation procedures and for all unpressurized flights.

Note:
Unpressurized flights are permitted only below 9,000 ft (2 743 m). Maintain a minimum aircraft speed to ensure sufficient airflow in the cabin and flight compartment.

During ground static operations, ram airflow is generated by the suction effect of the ACM.

Displays

Usually, the ram air valve is shown opened when the RAM AIR PBA (on the AIR COND/BLEED control panel) has been set to on and the valve has reached the full open position. Otherwise, the valve is shown closed.

The status of the ram air valve (valve opened/valve closed) and its related flow line is always shown on the environmental control system (ECS) synoptic page.

The color of the outline of the ram air valve can be as follows:

• Amber if a fault condition of the valve has been sensed (related to the RAM AIR FAIL advisory message)
• Magenta if the position of the valve is not known
• White otherwise

The color of the flow line related to the ram air valve can be as follows:

• Amber if a fault condition of the valve has been sensed and the valve is shown closed
• Green if the valve is shown open
• White otherwise

The PACK COOL AIR FAIL advisory message will show when a fault condition is sensed.

The RAM AIR FAIL advisory message will show when the position of the ram air valve does not agree with the RAM AIR selection made on the AIR COND/BLEED control panel.

The RAM AIR ON status message will show when the RAM AIR PBA (on the AIR COND/BLEED control panel) is set to on and the ram air valve is open.

The EICAS messages that follows are related to the ram-air system:

EICAS MESSAGE	LEVEL (COLOR)
PACK COOL AIR FAIL	ADVISORY (cyan)
RAM AIR FAIL	ADVISORY (cyan)
RAM AIR ON	STATUS (white)

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The condition of the ram-air regulating-valve is monitored during the system's power-on built-in test (BIT). Two fault conditions are possible. They are as follows:

• Fault condition in the closed position
• Fault condition in the open position

During the power-on BIT, the ram-air regulating valve is operated as follows:

• Valve is first energized to the closed position
• When the valve is in the closed position, an open command is sent to the valve and the system makes sure that the valve leaves the closed position
• A close command is then sent to the valve and the system makes sure that the valve reaches the closed position

A fault condition in the closed position is sensed when the valve stays in the fully closed position when commanded to open. Confirmation time for the fault condition is 7 seconds.

A fault condition in the open position is sensed when the valve stays in the fully open position when commanded to close. Confirmation time for the fault condition is 7 seconds.

When a fault condition is sensed, a PACK COOL AIR FAIL advisory message is shown on the EICAS.

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
-	WATER SPRAYER	ZONE(S) 311/312	21-53-01
-	WATER SEPARATOR TUBE	ZONE(S) 311/312	21-53-03
MPE9	RAM-AIR REGULATING-VALVE	ZONE(S) 311/312	21-53-05
-	RAM AIR DUCT	ZONE(S) 311/312	21-53-09
-	RAM-AIR INLET DUCT	ZONE(S) 311/312	21-53-13
-	RAM-AIR OUTLET DUCT	ZONE(S) 311/312	21-53-17
MPE40	RAM AIR VALVE	ZONE(S) 311/312	21-53-21

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