Air Conditioning DSC 21 Flashcards
Air to the airconditioning system is supplied by the pneumatic system via…?
- Two pack flow control valves
- Two packs
- The mixing unit
Where does the air come from which enters the mixing unit?
The cabin (recirc fans), and
The packs (cold fresh air), or
The RAM AIR inlet, or
Low pressure ground inlets
In an emergency where does Ram air provide ambient air to?
The mixing unit
Temperature regulation of the Flight Deck and Cabin is ensured by…..?
A Zone controller and 2 pack controllers (YUD), or
2 Air Conditioning System Controllers (ACSC
all except YUD)
How is temperature regulation optimised
By the hot air pressure regulating valve, and
the trim air valves
that add hot air, tapped upstream of the packs to the mixing unit
How much can the temperature be modified by the Cabin Crew from the Temperature Control Panel on the FAP?
+-2.5 deg C
What kind of air can be supplied to the mixing unit by a ground connection?
Low pressure air
Pack operation is controlled by…?
Signals coming from-
The Pack Controller (YUD), or
Air Conditioning System Controller (Others)
Warm air from the Precooler flows through the Pack Flow Control Valve and then flows….
- To the primary heat exchanger
- Air Cycle Machine’s compressor (↑ Pressure & Temp)
- Heat exchanger again
- ACM turbine (expands, drives compressor and cooling fan) and ↓temperature
When will the Pack Valve close automatically?
- Pack Overheat (on the ground only)
- Engine Start
- Operation of FIRE or Ditching pb
What happens when the RAM AIR pb is selected ON?
Outflow valve opens about 50% provided:
- its under automatic control, and
- ∆P is <1 psi
When will the Hot-Air PRV close automatically?
If:
- The duct overheats
- Cockpit Trim air valve fails
- Both Cabin trim air valves fail
- Both lanes of ACSC 1 fail (all except YUD)
Does the Hot-air PRV remain operative if only one Cabin trim air valve fails?
Yes
How are the trim air valves controlled?
Electrically via the: Zone Controller (YUD), or ACSC (all except YUD)
In all other aircraft except YUD, which ACSC controls which trim air valves?
Cockpit trim air valve is controlled by ACSC 1
Cabin trim air valves are controlled by ACSC 2
Which ACSC (all except YUD) regulates the Hot-air valve?
ACSC 1
Each pack controller /ACSC regulates the temperature of its associated pack by….?
Modulating the bypass valve and
The Ram air inlet flap
When do the Ram air inlet flaps close during take-off?
When TO power is set, and
the main landing gear struts are compressed
When do the Ram air inlet flaps close during landing?
As soon as the main landing gear struts are compressed,
Speed >=70kts
When do the Ram air inlet flaps open after landing?
20 sec after the speed drops <70kts
The pack controllers /ACSC’s regulate flow by….?
Modulating the associated pack flow control valve
When does the Pack Flow selector deliver higher flow than selected?
- Single Pack operations
- When the APU is supplying bleed air
When will the system deliver normal flow with the Pack Flow selector in LO
If the temperature demand cannot be satisfied
What does the Zone Controller (YUD) / ACSC do if the cooling demand in one zone cannot be satisfied?
If the bleed pressure is too low, it
sends a pressure demand signal to both Engine Interface Units (EIU) to
increase the minimum idle and increase bleed pressure
