Questions about Air Conditioning Systems

Q1. Under what conditions, Pack Flow Control Valve will close automatically ?A1. Pack Flow Control Valve [Pneumatically Operated/Electrically Controlled] closes automatically under the following conditions :(a) Pack Overheating

(b) Engine Starting
(c) Operation of Fire or Ditching P/b.
The Pack Flow Control Valve remains closed in absence of air pressure.


Q2. What is the RAM AIR P/B for? When is it used?
A2. Emergency Ram Air inlet ventilates cockpit/cabin to remove smoke or if both packs fail.The Emerg. Ram Air Inlet Valve is controlled by RAM AIR P/b on AIR COND panel. It opens the Ram Air Valve, provided that Ditching is not selected.

Q3. What is the limitation for opening the RAM AIR inlet?
A3. Ram Air Inlet will only open if Ditching is not selected. Also, during T/O, RAM AIR Inlet/Outlet flaps close when T/O PWR set and MLG struts are compressed.
During LDG, they close as soon as MLG struts are compressed and speed at or above 70 knots. They open 20 seconds after speed drops below 70 knots.
Also, if Delta P > 1 Psi, check valve located downstream the Ram Air door will not open even if Ram Air Door has been selected open. No airflow will then be supplied.

Q4. What are the conditions in which Hot Air Fault light comes?
A4. HOT AIR Fault light (Amber) comes on when :-
(a) Duct Overheat is detected [Overheat is sensed when Duct temp. reaches 88 degree Celsius]
*Goes off when temp. drops below 70 degree Celsius and flight crew select OFF.
(b) HOT AIR pressure regulating valve disagrees with selected position.

Q5. If Hot Air Press Reg. valve fails in open condition, what happens? What you are supposed to do, if in flight?
A5. There is no effect if the Hot Air Press. Regulating Valve fails in open condition.

Q6. If Hot Air Press Reg. valve fails in closed condition, what happens? What you are supposed to do, if in flight?
A6. Optimized regulation is lost. Trim Air Valves are driven to the full closed position. PACK 1 controls the cockpit temperature and PACK 2 controls the cabin temperature (FWD and AFT) to mean value of selected temperatures.

Q7. How many trim air valves are fitted and what do they do?
A7. There are 3 Trim Air Valves o the A320. One for each zone :-(a) COCKPIT
(b) FORWARD CABIN
(c) AFT CABIN
The Trim Air Valve, associated with each zone adjusts the temperature by adding hot air tapped upstream of the packs to the Mixing Unit Air.

Q8. If cockpit trims air valve has failed in open position, which of the warnings will be generated?
A8. TRIM AIR VALVE failed in open position, the following warning is generated :-
TRIM AIR SYS FAULT
And on ECAM COND page, "ZONE TRIM AIR VALVE" position indication will become amber.

Q9. What are the three supply zones for conditioned air?
A9. The Three Supply Zones for Conditioned AIR are :-
(a) COCKPIT
(b) FWD CABIN
(c) AFT CABIN

Q10. What happens when a temperature selector rotary knob is adjusted in the cockpit?
A10. A signal is sent to the Zone Controller requesting a different temperature [Rotary Knobs to select reference temperature which are fine tuned through the Forward Attendant Panel (FAP) for cabin zones ] . The ACSC's compute a temperature demand from the selected temp. and the actual temp. A signal corresponding to the lowest demanded zone temp. goes to Air Conditioning System controllers which then make both Packs produce the required Outlet Temperature.

Q11. What is ACSC and what does it do?A11. ACSC is short for Air Conditioning System Controller. It does the following :-
(a) PACK Operation Control
(b) Controlling the PACK flow control Valve
(c) Controlling the HOT AIR PRESS Regulating Valve
(d) TRIM AIR Valve CONTROL.
(e) Temperature and flow regulation.
Each ACSC regulates the temperature of its associated PACK by modulating the bypass valve and the Ram Air Inlet flap.

Q12. On which of the ECAM pages, the packs' parameters are shown? What are they?
A12. On the ECAM BLEED page :-
(a) PACK Outlet temp.
(b) PACK Bypass Valve position
(c) PACK Compressor Outlet temp
(d) PACK flow

Q13. On ECAM COND page, two temperature values are shown. What is the meaning of it?
A13. The two temperature Indications are :-
(a) Zone Temp Indication : The Zone Temp indication for the three zones, indicates the temp. in the zones.
(b) Zone Duct Temp Indication : The temperature of the air in the three main supply ducts to the Cocpit, The Forward Cabin and the Aft Cabin.

Q14. The ram air inlet flaps, {for the ACM heat exchangers}, automatically close under two conditions regardless of heat exchanger requirements. What are those two conditions? Where can you see them during walk-around inspection?
A14. RAM AIR Inlet/Outlet flaps close automatically under the following two indications :-
(a) TAKEOFF – T/O PWR set and MLG struts compressed.
(b) LANDING – As soon as MLG struts compressed and speed greater than or equal to 70 knots.

Q15. Is cargo heat provided to the forward cargo compartment?
A15. No.

Q16. Name the important components of the Air conditioning system?
A16. The following are the important components of the A320 Air Conditioning System
(a) Air Conditioning Pack
(b) Air Cycle Machine
(c) Heat Exchanger
(e) Mixing Unit
(f) Water Separator
And the Controller
(a) Air Conditioning System Controller

PRESSURIZATION

If there is any conflicting information, your FCOM shall be the overriding reference.

Q1. How many modes of pressurization exist on A320?
A1. There are Three modes of Pressurization on the A320
(a) AUTOMATIC
(b) SEMI-AUTOMATIC
(c) MANUAL

Q2. In auto mode of operation, what will be the max cabin altitude if system is functioning normal?
A2. 8000 ft is the Max Cabin Altitude in AUTO mode of operation.

Q3. If pilot suspects that the selected controller is malfunctioning, how can he change the controller {CPC}, while operating pressurization in AUTO?
A3. If the pilot suspects that the operating pressurization system is not performing properly, he can attempt to select to other system by switching the MODE SEL P/b to MAN for at least 10 seconds, then returning it to AUTO.

Q4. When will CPC changeover take place automatically?
A4. Automatic CPC Changeover happens automatically :-
(a) 70 seconds after each Landing.
(b) If the Operating System fails.

Q5. If one cabin pressure controller fails, how is pressurization maintained? What ECAM Caution will be generated?
A5. Pressurization System consists of 2 CPC's , one of which operates the OutFlow Valve by means of its associated Automatic Motor. In case of a single CPC failure, the remaining CPC takes over automatic control of pressurization. The following ECAM Caution will be generated :-
SYS 1 (or 2) FAULT
and correspondingly the PRESS PAGE on the SD will be automatically displayed.

Q6. If Cabin Pressurization is in Auto, and if you have to push open Emer. RAM AIR, what happens to the Out Flow Valve?
A6. When the Cabin Pressurization is in AUTO and you push open EMER. RAM AIR, the OutFlow Valve opens about 50% provided that Delta P is less than 1 Psi.

Q7. What happens to the outflow valve if the MODE SEL switch is in MAN?
A7. If the MODE SEL s/w is in MAN, the OutFlow Valve won't open even if Delta P is less than 1 Psi.

Q8. If you increase Cabin V/S {when pressurization in MAN Mode}, what happens to the Out-Flow Valve?
A8. The MAN V/S CTL toggle S/w is used to increase/decrease the Cabin V/s. The following happens to the OutFlow Valve on operation of the MAN V/S CTL Toggle s/w :-
UP : The Valve moves towards the open position.
DOWN: The Valve moves towards the closed position.
The OutFlow Valve operates slowly in MAN mode, so the pilot must hold the toggle switch in the UP or DOWN position until reaching the target V/s.

Q9. While in MAN Mode, how do you increase the cabin ALT?
A9. In MAN mode, you can increase the Cabin Altitude by operation on the MAN V/S CTL toggle s/w. By moving the s/w towards UP, the OutFlow valve moves towards the OPEN position, this increases the Cabin ALT.

Q10. By increasing cabin altitude in flight, what happens to Cabin Diff Pressure? Will it increase or decrease?A10. The Cabin Differential Pressure will decrease when the Cabin Altitude is increased in flight.

Q11. What is the role of Safety Valves?A11. The two independent pneumatic safety valves prevent Cabin Pressure from going too high (8.6 Psi above ambient ) or too low ( 1Psi below ambient ).

Q12. How many safety valves are fitted on A320?
A12. There are 2 independent pneumatic Safety Valves fitted on the A320, located on the rear pressure bulkhead above the floatation line.

Q13. What do you understand by negative differential pressure?
A13. Differential Pressure is the difference between the Cabin Pressure and the Ambient Pressure.
Delta P = Cabin Press. – Ambient Press.
Thus a Negative Differential Pressure means lesser Cabin Pressure than the Ambient Pressure.

Q14. With the LDG ELEV selector in AUTO, which reference altitude is used for landing field pressurization?
A14. The Controller normally uses the landing elevation and the QNH from the FMGC, and the pressure altitude from ADIRS. If FMGC data are not available, the controller uses the CAPT BARO Reference from the ADIRS and the LDG ELEV selection.

Q15. With the LDG ELEV selector at 1, what would be the landing elevation?A15. With the LDG ELEV selector at 1, the Landing elevation would be +1000 feet.

Q16. What is RPCU? What are the logic conditions for RPCU to open the Out Flow Valve?
A16. RPCU is short for Residual Pressure Control Unit. It automatically depressurizes the aircraft in case of abnormal residual pressure on ground. It automatically open OutFlow valve if :-
(a) The OutFlow Valve is not fully open and,
(b) Both CPC's are failed, or manual mode is selected, and
(c) The A/C is o the ground and
(d) All engines are ShutDown, or all ADIRS indicate airspeed < 100 knots.

Q17. What happens when the DITCHING pushbutton is selected ON?
A17. When the DITCHING P/b is selected ON, the operating system sends a "close" signal to the OutFlow valve, Emergency Ram Air Inlet, Avionics Ventilation Inlet and Extract Valves and the PACK Flow Control Valves close.

Q18. "Cabin V/S" info is displayed on three ECAM pages. Which are those?
A18. CABIN V/S info is on the following ECAM pages :-
(a) ECAM PRESS page
(b) ECAM CRUISE page
(c) ECAM DOOR page ( Only in Flight phases 5/6/7 )
*Flight Phase 5- Lift Off to 1500 ft.
*Flight Phase 6- 1500 ft – 800 ft
*Flight Phase 7- 800 ft to TouchDown.

Q19. When will V/S pulse in green?
A19. The V/S pulses in green when V/S > 1750 ft/min. It resets at 1650 ft/min.
Q20. When will Diff press pulse in green?
A20. The digital presentation of Differential Pressure will pulse green when Delta P > 1.5 Psi ( Resets at 1 Psi ) during Flight Phase 7.
*Flight Phase 7 : 800 ft to Touchdown

Q21. When will Diff press become amber?
A21. Delta P becomes Amber when Delta P less than or equal to -0.4 Psi or greater than or equal to 8.5 Psi.

Q22. When does CAB ALT become red?A22. The Cabin Alt Presentation appears in red when the Cabin Altitude goes above 9550 feet.

Q23. Can Out flow valve indication become amber? When?
A23. The OutFlow Valve indication becomes amber when the valve opens more than 95% during flight.

Q24. Name the important components of Pressurization?
A24. Following are the important components of Pressurization :-
(a) CPC : Cabin Pressure Controller
(b) RPCU : Residual Pressure Control Unit
(c) OutFlow Valve with its three motors
(d) Safety Valve

VENTILATION

If there is any conflicting information, your FCOM shall be the overriding reference.

Q1. What happens when you press Blower P/B to OVRD?
A1. When the BLOWER or the EXTRACT P/b switch is set at the OVRD (Override) position, the system is in closed circuit configuration and adds air from the Air Conditioning system to the ventilation air.
When the BLOWER P/b s/w is set at OVRD. , the Blower fan is stopped and the Extract fan continues to run.

Q2. What happens when you press Extract P/B to OVRD?
A2. When the BLOWER or the EXTRACT P/b s/w is set at the OVRD (Override) position, the system is in closed circuit configuration and adds air from the air conditioning system to the ventilation air.
When the EXTRACT P/b s/w is set at OVRD. , the Extract fan is controlled directly from the p/b. Both fans continue to run.

Q3. What will happen when you press both Blower & Extract P/B to OVRD? Name some situations when you have to push both Blower & Extract p/b to OVRD?
A3. When both BLOWER and EXTRACT P/b's are set at OVRD position, the Air Conditioning system supplies cooling air, which is then exhausted overboard. The Blower fan stops and the Extract fan continues to run.
In case of smoke detection in the avionics ventilation air, the BLOWER and the EXTRACT FAULT lights come on, in this case both the BLOWER and the EXTRACT fan switches are selected to OVRD.
In case of SKIN VALVE FAULT, with the Extract valve affected, the BLOWER and the EXTRACT fan switches are selected to OVRD. (These actions send additional closure signals to the inlet and extract valves. The weather radar image on both ND's may be lost in case of insufficient ventilation. )

Q4. What happens when Blower Fan stops on ground with engines shut down?A4. When the Blower fan stops on the ground with the engines stopped :-
FAULT Lt on the BLOWER P/b lights up.
ECAM activates.
The External horn sounds while on the ground.

Q5. What indications are given on the ventilation panel, if smoke is detected in the avionics ventilation duct?
A5. On the Ventilation Panel, the FAULT Lt. on both the BLOWER and the EXTRACT P/b's lights up Amber. ECAM activates.

Q6. What is the Avionics Ventilation System configuration once you apply take-off power?
A6. On the Ground after the application of T/O power, the Ventilation system is in closed circuit configuration.

You May Also Like These