21 - Aircon Flashcards
what are the 3 configs of the skin valves of the AEVC (Avionics Equip Vent Cpu) ?
Open - Ground only, both valves open
Closed - Air temp reduced by skin heater exchanger
Intermediate - Inlet closed, outlet partly open
In normal operation which A/Con packs supply which zones?
Pack 1 Cockpit
Pack 2 Cabin
How are FCV (Flow Control Valve) controlled?
Electrically controlled, pneumatically actuated, if their is insufficient air Px a spring keeps the valve shut.
How is temperature controlled in each zone?
Modulated by the TAV (Trim Air Valve),
controlled by the ACSC (Air Con System Controller)
Demanded by cockpit A/C hot/cold twist knobs or the FAP
How is pressurization controlled?
Outflow modulates to release desired quantity of air. Which is controlled by the CPC (Cabin Px controllers) which modulate the outflow valve
How is the fuselage protected from excessive differential Px and negative differential Px?
2x Safety valves fitted to rear Px bulkhead.
The TAVs (Trim Air Valves) are supplied with hot air that comes through the Trim Air PRV, at what Px is this hot air supplied?
4 PSI above cabin Px
+6.5 PSI triggers ECAM over Px warning.
During Eng start the packs are shut off, how is this achieved?
FCV (flow Control Valve) auto shuts if same side eng start detected, or X-bleed is detected open. Reopens 30secs after eng start sequence
How are the ACSC connected to the CFDIU?
Only connected to ACSC2.
All BITE data of ACSC 1 will be transmitted to ACSC
2 first before it goes to the CFDIU.
Explain the bypass valve in the air con system
Bypass valve, allows warm air to passed the Air Cycle Machine by the pack controller (ACSC)
When will pack flow default to HI?
Apu bleed selected or only 1x PACK operational
In a single BMC failure what is not protected?
APU (BMC1) and Pylon (BMC2) leak detection.
What temp does the FCV (Flow Control Valve) keep the bleed air entering the pack below?
215 degrees C
Above 260 degrees C, pack overheat warning
When is LOW flow automatically used?
During take off and landing
What does PACK stand for?
Pneumatic Air Cycle Kit
What is Cabin Alt regulated to in the cruise?
-8,000FT (Delta P 8psi, A/C alt of 39000ft)
-@9500ft cabin Px FWC signals lvl.3 warning
-CIDS triggers PAX seat belts @11300ft
How many outflow valves are there?
1, with 3x controls
2x automatic by CPC 1&2
1x manual, controlled from Px panel, by manual part of CPC1
What type of heat exchangers do the primary and secondary exchangers in the PACKS use?
Air to Air ( external RAM air through pack inlets)
How is short term temperature controlled by the ACSC
Modulating the Bypass Valve
How is long term temp control by the ACSC?
Modulating the Ram Air (PACK inlet) to the heat exchangers.
What is the purpose of the ACM (Air Cycle Machine) fan?
Used on the ground to draw ambient air over the heat exchangers.
How is the CFDIU connected to the ACSC?
Only via ACSC 2, ACSC 1 sends all its BITE data to ACSC 2.
How is PACK inlet Px controlled?
PACK inlet Px sensor, signals ACSC, if there’s a differential in DELTA P. commands it to open the bypass valve (increasing Px), also opens RAM air inlet to compensate for reduced turbine efficiency.
Explain how the Compressor discharge Temp sensor works:
Pack temperature control:
- up to 180°C (385°F): normal operation,
- 180°C to 220°C (428°F): the ram air inlet flap opens more in order to increase RAM airflow.
-260°C (500°F). PACK FAULT light comes on. If the A/C is on ground, automatic FCV closure occurs.
What’s the cabin (dirty) to conditioned (clean) air mix?
37% to
51% (the cabin fans operate at a constant speed, but the airflow from
the Pack Flow Control Valve (FCV) can vary.)
What would would the ACSC do in the event of Ditching P/bsw selection?
Both pack FCV (Flow Control Valves) would shut. Same would happen if either eng fire P/Bsw are selected.
How is the signal sent from FAP (Flight Attendant Panel) for temp ctrl?
CIDS signals ACSC 1&2
What would the outflow valve do if Emer RAM were selected?
CPC (Cabin Pressure Cotroller) would move Outflow vlv to halfway position, when Delta P (Px diff) is less than 1PSI
In the event of CARGO smoke detection what happens?
CVC (cargo ventilation controller) will
automatically close the related isolation valves. SEperating the compartment from the rest of the A/Con system.
