Through two isolated ducts, the flight compartment distribution system supplies temperature-controlled air to the flight compartment and conditioned air (cool air) to the flight compartment gaspers.

The temperature-controlled air is a mixture of cool air that comes from the air-conditioning system (pack) and hot air that comes from the temperature control system. The quantity of cool air and hot air that makes up the mixture is controlled from the COCKPIT temperature selector found on the AIR COND/BLEED control panel. The cool air that goes to the flight compartment gaspers comes from the pack.

The flight-compartment distribution system can also supply ram air. To do so, the RAM AIR push button annunciator (PBA) on the AIR COND/BLEED control panel must be pushed in.

The flight compartment ducting system is designed for low internal air velocities (below 2,000 ft/min or 609.6 m/min). The low internal air velocities keep pressure losses to a minimum and guarantee minimum noise caused by airflow.

The ducting system is made up of low pressure flexible and rigid ducts found above and below the aircraft floor. The ducts are attached together and to the outlets with tie-down straps or hose clamps. This configuration keeps weight to a minimum and helps in the ducts' installation and removal.

The flexible ducts are made as follows:

• With a layer of silicone-coated glass-fabric hose. The hose is made stronger with a coil of metallic or non metallic wire.
• Inlet and outlet ends have two or three layers of silicone made stronger with fiberglass.
• Where necessary, the ducts have a layer of thermal insulation.

The rigid ducts are made as follows:

• With one or more layers of phenolic resin composite material made stronger with fiberglass. The ducts are locally made stronger with more layers of material at the pneumatic and structural connections.
  
  
• With an internal electrically conductive layer.
• Where necessary, the ducts have a layer of thermal insulation.

Electrical bonding with the aircraft structure and the temperature sensor is done through fittings, lugs, studs, or check valves that are electrically bonded to the conductive layer of the rigid ducts.

Note:
There is one temperature sensor installed in the flight-compartment distribution system. It is identified as the flight-compartment duct temperature-sensor. The flight-compartment duct temperature-sensor is found on the flight-compartment ducts (aft fuselage) and it is a component of the temperature control and indication system.

---

The bulkhead check valve (BCKV) isolates the pressurized area of the aircraft from the not pressurized aft compartment of the aircraft. Its function is to prevent cabin depressurization if a failure of the pack discharge duct occurs.

Note:
The pack discharge duct is a component of the air conditioning system.

The BCKV has a 4 in. (10.16 cm) diameter body, a flapper that closes by gravity, and a flange to attach the valve on the aft pressure bulkhead. The flapper and the flange are made of a light alloy material.

The body of the BCKV is machined as a single unit and has a movement compensation connector for an airtight connection to the pack discharge duct.

The BCKV is attached to the aft pressure bulkhead with screws. Access to the BCKV is from the pressurized side of the bulkhead. This is to let air pressure push the valve against the bulkhead. Silicone sealant applied between the BCKV and the pressure bulkhead prevents air leaks.

Air pressure from the pack or, if applicable, from the ram-air system, pushes on the flapper of the BCKV. This causes the BCKV to let air flow through the flight-compartment distribution system.

The shape of the body of BCKV does not limit airflow and prevents the possibility of ice build-up on the flapper.

---

The flight-compartment gasper ducts supply cool air (that comes from the pack) to the flight compartment. The cool air comes from the mix manifold, upstream of the inlets that let hot air from the temperature control system go into the mix manifold.

Note:
Because it comes from upstream of the hot air inlets, the air that flows through the flight-compartment gasper ducts is cool air (not temperature controlled air).

The flight compartment gasper ducts include the components that follow:

• A gasper feed hose
• A gasper tee junction
• Two gasper hoses. Each hose supplies cool air to its related side of the flight compartment.

Note:
A gasper outlet is attached at the open end of each gasper hose. The gasper outlets are not shown in the illustrations found in this section because they are completion items and can be different from one aircraft to another.

The gasper tee junction is made out of glass and phenolic resin components.

Much of the flight-compartment gasper ducts is hidden behind interior finish panels.

Note:
The routing of the flight-compartment gasper ducts, between the flight compartment and the mix manifold, is not shown in the illustrations found in this section. This is because that part of the ducts is a completion item and its routing can be different from one aircraft to another.

---

The flight compartment vents are found in the side consoles. They are part of a group of openings that lets temperature controlled air into the flight compartment.

Each flight compartment vent includes the components that follow:

• A ventilator
• A side oval hose

To attach the ventilator to the side console finish panel, the face flange of the ventilator has a support plate made out of aluminum.

---

The aft fuselage flight-compartment ducts connect the mix manifold to the center fuselage flight-compartment ducts. They are part of a series of ducts that lets temperature controlled air move from the mix manifold to the flight compartment.

The aft fuselage flight-compartment ducts include a rigid and a flexible duct section. The flexible duct section has a boss that hosts the flight-compartment duct temperature-sensor.

The aft fuselage flight-compartment ducts are found below the aircraft floor, in the rear pressurized cabin area.

---

The center fuselage flight-compartment ducts connect the aft fuselage flight-compartment ducts to the flight-compartment feed ducts. They are part of a series of ducts that lets temperature controlled air move from the mix manifold to the flight compartment.

The center fuselage flight-compartment ducts include flexible and rigid duct sections. They are found below the aircraft floor, in the center pressurized cabin area.

---

The flight-compartment feed ducts connect the center fuselage flight-compartment ducts to the flight-compartment outlet ducts and to the flight compartment vents. They are part of a series of ducts that lets temperature controlled air move from the mix manifold to the flight compartment.

The flight-compartment feed ducts include the components that follow:

• Three Flexible duct sections
• Feed tee
• Two Side junctions

The components that make up the flight-compartment feed ducts are found below the aircraft floor, in the forward pressurized cabin and flight compartment areas.

---

The flight-compartment outlet ducts connect the flight-compartment feed ducts to the crew face and crew foot outlets. They are part of a series of ducts that lets temperature controlled air move from the mix manifold to the flight compartment.

For each side of the aircraft, the flight-compartment outlet ducts include the components that follow:

• Forward feed hose
• Forward tee hose
• Foot warmer hose
• Face Wemac hose

The flight-compartment outlet ducts are found above and below the floor, in the flight compartment area.

---

The flight-compartment distribution system supplies temperature controlled air to the flight compartment and cool air to the flight compartment gaspers. The flight-compartment distribution system is designed to give maximum flight compartment comfort. Its configuration gives the most equal air temperature distribution in the flight compartment. It also keeps air drafts to a minimum. Flight-compartment air distribution is done through a ducting system that has thermal insulation. The thermal insulation gives better system performance. At one end, the ducting system is connected to the left most outlet of the mix manifold. At the other end, the ducting system lets temperature controlled air out into the flight compartment through the openings that follow:

• Two primary exhausts (grilled) found in the side-consoles. The openings are identified as the flight compartment vents.
• Two crew face outlets (with adjustable airflow output through disk valves).
• Two crew foot outlets (grilled).

Note:
The mix manifold is a component of the passenger-compartment distribution system.

The gasper ducts are also components of the flight-compartment distribution system. They supply cool air into the flight compartment through two outlets found above the pilot and copilot positions. For the temperature controlled air that goes to the flight compartment, the path of the airflow is as follows:

• Cool air from the pack goes to the mix manifold through the pack discharge duct and the BCKV.

Note:
The pack discharge duct is a component of the air conditioning system.

• In the mix manifold, the cool air (that comes from the pack) mixes with the hot air that comes from the temperature control system. That mixture gives temperature controlled air.
  
  
• The quantity of cool air and hot air that makes up the mixture of temperature controlled air is controlled from the COCKPIT temperature selector found on the AIR COND/BLEED control panel.
  
  
• The temperature controlled air then goes to the flight compartment through a series of ducts.
• The temperature controlled air comes out of the ducts through the flight compartment vents, the crew face outlets and the crew foot outlets.

For the cool air that goes to the flight compartment gaspers, the path of the airflow is as follows:

• Cool air from the pack goes to the mix manifold through the pack discharge duct and the BCKV.
• In the mix manifold, cool air is then drawn off immediately upstream of the openings that let the hot air from the temperature control system enter the mix manifold. That cool air (drawn off of the mix manifold) then goes through the flight-compartment gasper ducts.
  
  
• The cool air that flows through the flight-compartment gasper ducts is then released through the gasper outlets.

The flight-compartment distribution system can also supply ram air. To do so, the RAM AIR PBA on the AIR COND/BLEED control panel must be pushed in. When this is done, the ram air valve opens and lets ram air flow into the pack discharge duct. From the pack discharge duct, ram air then goes to the mix manifold through the BCKV. From the mix manifold, the ram air goes to the flight compartment through the usual flight-compartment distribution system.

The temperature of the air that flows through the aft fuselage flight-compartment ducts is sensed by the flight-compartment duct temperature-sensor. The data from the sensor goes to the integrated air system (IAS) controllers.

Note:
The IAS controllers are components of the cabin-pressure control system.

The IAS controllers monitor the temperature of the air that flows through the flight compartment ducts for a possible overheat fault condition.

Displays

The AIR COND TEMP HIGH caution message shows when an excessive air temperature has been sensed in the flight compartment air distribution duct.

The TRIM AIR FAIL caution message shows when a hot air regulating valve has malfunctioned or the flight-compartment duct temperature-sensor is out of range or has sent no data.

The EICAS messages that follows are related to the flight compartment distribution system.

EICAS MESSAGE	LEVEL (COLOR)
AIR COND TEMP HIGH	CAUTION (amber)
TRIM AIR FAIL	CAUTION (amber)

---

The continuous built-in tests (BIT) that follow are related to the flight-compartment distribution system:

• When the temperature of the air that flows through the flight compartment ducts becomes higher than 185 °F (85 °C) for more than 30 seconds or higher than 212 °F (100 °C) for more than 10 seconds, an AIR COND TEMP HIGH caution message is shown on the EICAS.

Note:
When the AIR COND TEMP HIGH caution message is shown on the EICAS, the AIR SOURCE rotary switch on the AIR COND/BLEED control panel should be set to PACK ONLY.

• When the temperature acquisition range of the flight-compartment duct temperature-sensor is sensed to be out of range, −55 to +200 °F (−48.33 to 93.33 °C), a TRIM AIR FAIL caution message is shown on the EICAS. Confirmation time for the fault condition is 5 seconds.

Note:
When the TRIM AIR FAIL caution message is shown on the EICAS, the AIR SOURCE rotary switch on the AIR COND/BLEED control panel should be set to PACK ONLY or OFF position.

---

Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
-	BULKHEAD CHECK VALVE	FS669.759	21-21-01
-	FLIGHT COMPARTMENT GASPERS	ZONE(S) 200	21-21-05
-	FLIGHT COMPARTMENT VENT	ZONE(S) 211/212	21-21-09
-	FLIGHT COMPARTMENT DUCTS (AFT FUSELAGE)	ZONE(S) 141	21-21-11
-	FLIGHT COMPARTMENT DUCTS (CENTER FUSELAGE)	ZONE(S) 141	21-21-13
-	FLIGHT-COMPARTMENT FEED DUCTS	ZONE(S) 141	21-21-15
-	FLIGHT-COMPARTMENT OUTLET DUCTS	ZONE(S) 211/212	21-21-17

---