The ram air system supplies air to decrease the temperature of the air in the dual heat exchanger. The emergency ram air system supplies fresh air if the pneumatic system or the air conditioning system goes unserviceable.

The ram air system supplies the air necessary to keep the air conditioning system cool. It is also used in an emergency to supply fresh air to the flight compartment if the two air conditioning units go unserviceable. When the RAM AIR switch/light on the bleed air control panel is set to ON, the ram air valve opens. This lets the ram air supply fresh air to the ventilation system. The ram air inlet duct supplies cold air to the two heat exchangers. It also supplies emergency ram air when the ram air valve is open. The ram air inlet duct is connected to the ram air intake installed on the leading edge of the vertical stabilizer. There are two ram air outlet ducts. After the ram air goes through the heat exchangers, the ram air outlet ducts release the heated air outside of the aircraft. A ram air check valve on the aft side of the ram air intake opens on the ground to supply more air for the system.

There are two water sprayers. Each water sprayer is installed in the main heat exchanger diffuser. A water extractor on each air conditioning unit removes water from the air and sends it to the water sprayers. It sends the water through a nozzle at high velocity into the ram air flow. The spray decreases the ram air temperature upstream of the dual heat exchangers.

The ram air valve supplies the ventilation system with fresh air when the pneumatic system or the air conditioning units are unserviceable. The ram air valve has a butterfly valve and an electric actuator. Microswitches on the actuator remove power when the valve is fully open or closed. A handle on the valve body opens or closes the valve manually on the ground.

The RAM AIR switch/light on the bleed air control panel opens the ram air valve when the switch is pushed in. The valve is installed on the right pack discharge duct in the aft equipment compartment.

The main heat exchanger diffuser is a chamber which supplies the air to the main heat exchanger. It is installed in the aft equipment compartment between the main heat exchanger and the ram air inlet duct.

The ram air inlet ducts supply the cold air to the dual heat exchangers of the air conditioning units. It also gives fresh air to the flight compartment when the ram air valve is open.

The ram air flows from the ram air intake to the ram air inlet duct. The ram air flow then divides into two parts to supply the two air conditioning units. The ram air inlet ducts are installed in the aft equipment compartment.

On the ground, a ram air check valve opens when the fan of the air cycle machine is on. This check valve increases the ram airflow available for each air conditioning unit. In flight, the check valve closes when the pressure in the ram air intake is sufficient. The ram air check valve is installed on the aft side of the ram air intake.

The ram air outlet ducts remove the heated air from the dual heat exchangers of the air conditioning units. The air is released outside of the aircraft through the ram air outlet. The ram air outlet ducts also reduces the noise of the air conditioning units. A scavenge line connects from the bleed filter to the ram air outlet ducts. Unwanted materials removed from the bleed filters are sent through the scavenge line to the ram air outlet ducts and then outside the aircraft through the ram air outlet. The ram air ducts are located in the aft equipment compartment.

On the ground, the ram air check valve opens when the fan of the air cycle machine is on. This check valve increases the ram air flow available for each air conditioning unit. In flight, the check valve closes when the pressure in the ram air intake is sufficient. The ram air check valve is installed on the aft side of the ram air intake.