Air Conditioning & Pressurization Flashcards
Describe the Recirculation Fan
Located in ACM service bay.
Initially starts at slow speed and ECU commands high speed as required.
Also runs at slow speed during single pack operations.
When the Pack Control Switch is in Auto how does it work?
In Auto Mode the ECU uses it digital channels to control Flow Control & Shut Off Valve and Pack Bypass Valve to control cabin temperature as measured by the two cabin temp sensors. 15-27 degrees C.
When the Pack Control Switch is in Manual how does it work?
In Manual Mode the ECU uses it analog channels to control Pack Bypass Valve via crew inputs to control duct temperature. The Flow Control & Shut Off Valve remains full open. 3-71 degrees C.
With both Pack Control Switches turned off what happens?
The FCSOV and Turbine Shut-off valves are both closed.
In single pack operations what happens to the recirc fan and airflow?
The recirc fan runs at low speed and the system only supplies approximately 70% of the normal flow.
What are the outflow valves on the airplane?
Aft Outflow
Aft Safety Outflow
Forward Safety Outflow
What are the four modes of operation for the pressurization system?
Automatic Mode
Manual Mode
Emergency/Smoke removal Mode
Pressure Dump Mode
Describe the Automatic Mode of the Pressurization System.
Cabin Pressure Controller (CPC) automatically schedules the pressurization from takeoff to landing with minimal input from the crew. Modulates the Aft Outflow Valve to regulate cabin pressure.
When the power levers are advanced passed 60 degrees on takeoff the CPC begins modulating the Aft Outflow valve as necessary to maintain pressurization schedule.
Describe the Takeoff Abort feature of the Pressurization System.
The CPC remains in takeoff mode for ten minutes after liftoff. This avoids the requirement for the crew to reset the landing altitude in the event of a return to field.
Describe the Manual Mode of the Pressurization System.
Manual mode modulates the Aft Outflow valve at the manual command of the crew using the DECR-INCR switch.
When the switch is held to the INCR position the Aft Outflow valve closes, INCREASING cabin differential pressure which lowers the cabin altitude.
Describe the Dump Mode of the Pressurization System.
When the Pressurization Mode switch is selected to DUMP the Aft Outflow valve is commanded open dumping all cabin pressure.
Used for smoke removal from the cabin.
How can the aircraft be ventilated when unpressurized?
With the aircraft unpressurized and the packs off, air enters the cabin through the dorsal fin NACA vents and through the Forward Outflow Valve.
Describe the Aft Outflow Valve.
Aft Outflow: Primary valve for controlling pressurization. Electrically controlled on aft pressure dome. Controlled by the Cabin Pressure Controller
Describe the Aft Safety Outflow Valve.
Aft Safety Outflow: Electro-pneumatic valve on aft pressure dome. Opens for additional venting on the ground with an engine or the APU running.
Incorporates positive and negative pressure relief valves.
Describe the Forward Safety Outflow Valve.
Forward Safety Outflow: Pneumatic valve on forward pressure bulkhead for emergency operations such as smoke evacuation.
Incorporates positive and negative pressure relief valves.
