Air Systems Flashcards
Recall the function of the AVIONICS COOLING Switch (FAN, OVRD)
The AVIONICS COOLING Switch is operative in flight only and is used to control radio rack cooling:
FAN - the primary fan cools the radios; if the primary fails, the backup fan comes on automatically
OVRD - the radio rack fans are off, the venturi valve is commanded open and venturi airflow cools the radios
NOTE: On the ground, both fans stay on all the time and the venturi valve is
commanded closed
Recall the function of the RAM AIR Switch (OFF, ON)
OFF - Ram air valve commanded closed
ON - Ram air valve commanded open, allowing ram air to enter the air conditioning ducts
• In flight, the system provides ventilation for the cabin and the cockpit when air
conditioning is not available
• Do not use the ON position to ventilate the aircraft on the ground
Recall the function of the PACK SHUTDOWN Switch (AUTO, OVRD)
AUTO - Allows automatic pack shutdown in the event of an engine failure
OVRD – Overrides the auto pack shutdown for an engine failure OR when the packs are selected OFF on the FMC
- Both AC packs will automatically shut down if either engine fails during takeoff OR if selected OFF through the FMS
- The auto pack shutdown feature is disarmed above 3000’ AGL
NOTE: A pack will also auto shutdown if a high supply duct temperature is sensed. This
cannot be overridden with the PACK SHUTDOWN switch
Recall the function of the FLOW Switch (NORM, HIGH)
NORM – The flow control valve solenoid is energized to provide a lower airflow rate
HIGH - The flow control valve solenoid is de-energized to provide a higher airflow rate
Lim: The FLOW Switch must be in NORM for takeoff
Recall the function of the ISOL Switch (CLSD, OPEN, AUTO)
CLSD - The isolation valve is commanded closed, isolating the left and right pneumatic systems
OPEN - The isolation valve is commanded open - allows crossfeed of left and right pneumatic systems
AUTO - The isolation valve is controlled by the pneumatic system controller. Allows automatic crossfeed of left and right pneumatic systems during one bleed source operation with airfoil ice protection selected ON
Recall where CABIN ALTITUDE and CABIN RATE are displayed (2)
Cabin pressurization information is displayed on the AIR SD synoptic Cabin Altitude and Cabin Rate information are also displayed on the SECONDARY ENGINE SD synoptic
Recall the function of the Instrument Panel Flow Indicator (ON, OFF)
ON – On the ground, with air conditioning off, indicates instrument panel cooling fan airflow
OFF – On the ground, with air conditioning off, indicates the
absence of airflow and cooling fan failure
Airflow indications apply only during ground and flight operations with both air
conditioning packs off
• During ground operations, with one pack selected AUTO, the instrument cooling fan is operating. With both packs selected AUTO, the instrument panel cooling fan is not operating – and instrument cooling is provided by the aircraft air conditioning system
• During ground operations, if the APU is required for cooling and both pilots must leave the cockpit, one AC pack should be selected OFF. This will preclude possible Display Unit overheats caused by an inadvertent APU shutdown with both packs selected on
• During flight operations, BOTH AC packs must be OFF for the instrument panel
cooling fan to operate
Recall the function of the Gasper Booster Fan switch (ON, OFF)
ON (Push) – Provides supplemental airplane ventilation with or without air
conditioning packs operating
OFF – booster fan is not on; switch is extinguished
NOTE : When selected ON, the left pack should be running. The fan increases cold
air ventilation through the eyeball outlets.
Recall the function of the CABIN PRESS control panel (“SELECT” “MANUAL”)
SELECT - Illuminates to indicate failure of both automatic cabin pressure controllers
MANUAL - When switchlight is pushed, MANUAL illuminates and the cabin pressurization system operates in manual mode. Also used to alternate control between cabin pressure controllers (Auto 1 and Auto 2)
Note: Switchlight is dark when the pressurization system is operating in automatic mode
Recall the Takeoff with Air Conditioning Packs Off procedure
Takeoff with Air Conditioning Packs Off
TO/APPR key…………………………Push
PACKS – Line select ON to OFF
Observe PACKS ALL OFF alert message on EAD
NOTE: With the air conditioning pack switches in AUTO, the packs will automatically shut off at throttle advance and will automatically come back
on at 3,000 feet AGL
Recall how forward and aft cargo bins are heated and where live animals must be
transported
- In flight, if the primary fan is operating, the forward cargo compartment is electrically heated to a temperature range between 60° and 75°F
- Live animals must be transported only in the forward cargo compartment.
- The aft cargo compartment is heated with cabin exhaust air
Recall the function of the Pneumatic Overheat Detection System (PODS)
- Detects overheat conditions in the tail compartment AND along the wing and tail ice protection manifolds
- If a failure is detected in the anti-ice manifolds, PODS automatically closes the respective anti-ice valve and alerts the flight crew
- PODS is automatically tested when the engine fire test is performed
