Air Conditioning and Pressurization Flashcards
Where is the RECIRC FAN located and where does it draw its air from?
Located in the ACM Service Bay and draws its air from the aft cargo compartment for distribution to the cabin and flight deck ducts.
The Air Conditioning System is made up of what components?
- Two engine Bleed Air Systems
- One APU
- One integrated Air Conditioning Pack
- One Environmental Control Unit
- Air Distribution and Recirculation Ducts
When does the RECIRC FAN operate at slow speed?
After initially being turned on
Engine start
Single ACM operations
The rotary, three position Duct Temperature Knob shows the temperatures for:
The Flight Deck DUCT temperature
The Cabin ZONE temperature (taken at mid cabin)
The Cabin DUCT temperature
Describe the ECU’s operation with the pack toggle switches in AUTO.
The ECU’s DIGITAL channels control the FCSOV and Pack Bypass Valves to automatically control the cabin and flight deck temperature based off the temperature knob inputs.
What is the selectable temperature range with the packs in AUTO?
15°-27° C
Describe the ECU’s operation with the Pack Toggle Switches in MANUAL.
The ECU’s analog channels control only the Pack Bypass Valves while the FCSOV remains fully open. Temperature control is based on duct supply temperatures instead of zone temperatures and the risk of duct overheat is greater.
What is the temperature range with the Pack Toggle Switches in Manual?
3°-71° C
What happens when the Pack Toggle Switches are selected to off?
The ECU closes both the FCSOV and Pack Bypass Valves, shutting off the ACM.
With both ACM’s operating, what percentage of air from the left pack goes to the flight deck?
Approximately half of the left pack. The remainder and all of the air from the right pack goes to the cabin.
What happens during single pack operations?
The RECIRC FAN operates at slow speed and the system will operate at approximately 70% of selected flow.
Are the flight attendants able to control cabin temperature?
Yes, with the cabin temperature knob turned fully counter-clockwise to the detent. A LED light illuminates on the flight attendant panel letting them know they control the cabin temperature.
What do the Bleed toggle switches control?
The Nacelle Shutoff Valves and the P2.2 valves
How is the airplane pressurized?
Bleed air supplied by the engines and distributed by the air conditioning system. Pressure is maintained by the Cabin Pressure Control System which regulates the amount of out flowing air.
What does the Cabin Pressure Control System consist of?
- Cabin Pressure Controller
- Aft Outflow Valve
- Aft Safety Outflow Valve
- Forward Safety Outflow Valve
What is the primary valve responsible for regulating cabin pressure?
The Aft Outflow Valve
- Electronically operated
- Used during automatic and manual operation
- Can be used to dump cabin pressure
What are the 3 modes of operation for the Aft Outflow Valve?
Automatic - Controlled by the Cabin Pressure Controller
Manual - Controlled by the Man Diff switch
Dump - Commanded fully open
What does the Aft Safety Outflow Valve do?
Assists the Aft Outflow Valve on the ground whenever one engine or the APU is running. It is an electric-pneumatic valve located on the aft pressure dome.
What does the Forward Safety Outflow Valve do?
Located on the Forward pressure dome, it’s a pneumatic valve used for emergency smoke removal. Can be operated by the knob on the pressurization panel (modulates) or the handle on the FO’s side (fully opens).
What valves incorporate positive and negative pressure relief valves?
The Aft Safety Outflow Valve and Forward Outflow Safety Valve
What are the four modes of the CPC?
Automatic
Manual
Emergency/Smoke Removal
Pressure Dump
What happens to the Aft Outflow Valve during takeoff?
The Aft Outflow Valve remains fully open on the ground. Once the power levers are above a PLA of 60° the CPC sends a signal to the outflow to modulate as necessary to maintain cabin pressure.
How long does the Cabin Pressure Controller remain in Abort Mode for?
10 minutes. This avoids having to reset the landing field altitude in the event of an emergency return after takeoff.
How is the airplane ventilated during unpressurized flight?
Air enters through the NACA vents on the dorsal fin and exits through the forward safety outflow valve.
