Operation Manual Part 2

Aerosoft – Digital Aviation
CRJ-70 & CRJ-900
AOM PART 2
Systems Description
VOL
5
5-1-36
26-Jul-2017
ENVIRONMENTAL CONTROL SYSTEM
The environmental control system controls mainly the cabin temperature and cabin pressure of the aircraft.
Even though this sounds very simple several different systems are needed to perform these tasks:
• Air condition units / Packs
• Cabin pressurization system
• Recirculation fans
AIR CONDITIONING SYSTEM / PACKS
With increasing altitude, the surrounding air gets thinner and colder as well. Above 12,000ft breathing is barely
possible and the air temperature is below freezing point. With aircraft cruising at high altitudes processing the
outside air before letting it enter the cabin is necessary. The air conditioning systems, also called packages, or
packs perform this task by mixing and filtering cabin air and outside air. Hot bleed air from the engines is used
to heat the air from outside before mixing it with the air from the cabin. Bleed air and outside air are not
missed though. In case the engines are not running, bleed air from the auxiliary power unit, APU, may be used
as well.
The CRJ is equipped with two packs. The left pack normally supplies the flight deck and the right pack supplies
the cabin.
1. LEFT (L) / RIGHT (R) PACK:
controls the operation of
the conditioning packs.
2. RECIRCULATION FANS:
controls the recirculation
fans
3. RAM AIR (guarded): Used
when both packs failed to
let ambient air into the left
(cockpit) air condition duct
4. MANUAL MODE VALVE
CONTROL: Directly controls
the valve positions for air
condition in manual mode (cockpit/cabin)
5. MANUAL MODE CONTROL: Selects manual temparature control (cockpit/cabin)
6. AUTOMATIC MODE TEMPERATURE CONTROL: Used to set desired temparature (cockpit/cabin)
7. AFT CARGO BAY AIR CONDITIONING: Activates air conditioning in aft cargo bay. Should be set to
COND after take-off
In case both packs fail and outside air needs to be ventilated into the cabin, you must descend to a suitable
altitude (12,000ft or lower) and activate the RAM air ventilation by pressing the guarded RAM air pushbutton.
OPEN illuminates in white after pressing / activating RAM air ventilation.
To ensure that the air cycles through the cabin, recirculation fans – which are installed in the mixing manifolds
– support cycling. To activate the recirculation fans, move the RECIRC FAN switch to ON.