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electronic boxes. These ducts direct the air towards the exhaust fan at the rear of the
avionics bay.
The avionics fan ON/OFF switching logic is based on aircraft altitude. The fan is ON
at an altitude of less than 30,000 feet with a default to always ON in the event of loss
of altitude data from the DAUs.
The avionics fan, which is controlled by ACSC 2, can run at a high or low speed. The
fan is driven at high speed when:
• ACSC 2 is OFF; or
• Both packs are OFF; or
• Main door is not closed and locked
The fan is driven at low speed when:
• ACSC 2 is ON; and
• At least 1 pack is on, and
• Main door is closed and locked
(Global 5000 – See Appendix 1)
MAIN
DOOR
UNDER FLOOR
AVIONICS EQUIPMENT
Forward Outflow
Valve
Avionics
Exhaust Fan
Display Units
GX_13_033
P I LOT T R A I N I N G GU I D E
INTEGRATED AIR MANAGEMENT SYSTEM
13-34 For Training Purposes Only
Sept 04
In the case of a failure, the avionics fan is automatically powered OFF by its converter.
The converter tries up to three times to restart the fan by automatic reset. If failure is
still detected, the converter will shut off the fan and post a message on the EICAS.
In the case of a fan underspeed failure detected by the converter, a fault signal is
provided but the fan remains running.
RECIRCULATION
Two recirculation fans pull air from the cabin back to the mix manifold. The air is
extracted from each side of forward and aft cabins through holes in the cabin side sills
and is ducted under the floor to the recirculation filters. From the filters the air enters
the recirculation fans and is blown into the mix manifold to be mixed with incoming
air from the packs.
AVIONICS FAN FAIL
Note:
Check limits on ground operations
with failed Avionics fan and ECS OFF.
Maximum operating time of 30 minutes.
GX_13_034
NORM:
In normal operation, recirculation fan speed is at
minimum but can be increased when the mix
manifold temperature is too low or too high.
MAN:
In manual mode, (i.e. no speed control by the
AFCS) the recirculation fan will run at minimum
speed.
GX_13_035
PACK CONTROL
NORM
MAN
LO HIGH
PACK CONTROL
LO
PACK CONTROL
NORM
MAN
LO HIGH
Recirculation
Fan
Recirculation
Filter
Outlet to
Overhead Gaspers
Mix Manifold
Recirculation Fan
Trim Air Valves
Extracted
Air
For Training Purposes Only
Sept 04
13-35
P I LOT T R A I N I N G GU I D E
INTEGRATED AIR MANAGEMENT SYSTEM
Each fan converter unit can detect internal failures (overheat, overcurrent). If a failure
is detected, the converter unit will shut off fan power and reset the fan. The converter
will attempt three times to restart the fan. If a failure is still detected, the converter will
shut off the fan and a message is posted on the EICAS. The crew can turn off the
RECIRC FAN via the PBA located on the BLEED/AIR CONDITIONING control
panel.
RECIRC
OFF
RECIRC FAN OFF
RECIRC OFF
GX_13_036
RECIRC
OFF
P I LOT T R A I N I N G GU I D E
INTEGRATED AIR MANAGEMENT SYSTEM
13-36 For Training Purposes Only
Sept 04
RAM AIR VENTILATION
The ram air system is picked up at the ram air inlet at the base of the vertical fin and is
used primarily (normal ops) to provide cooling for the heat exchangers of the cooling
packs.
A secondary role is to supply an alternate source of fresh air via the ram air system. It
has been designed for use in-flight at an altitude of 15,000 feet or less. The Ram Air
Valve may be selected open at any altitude, however ram air will not enter the airplane
if packs are operating or if the airplane is above 15,000 feet.
The ram air valve is closed in normal operations. It can be switched ON manually, by
means of a guarded switch on the air conditioning control panel. The ram air valve is
opened for unpressurized flight operations below 15,000 feet.
Ram Air
Inlet
GX_13_037
RAM AIR
ON
RAM AIR
ON
RAM AIR ON
Ram Air Inlet
Scoop
Ram Air
Valve
Right Pack
AIR CONDITIONING
RAM AIR
TRIM AIR
BLEED
LOW
BLEED
HIGH
12 °C 15 °C
15 °C 15 °C 15 °C
19 °C 21°C 22 °C
L PACK R PACK
CKPT
20°C
FWD
20°C
AFT
23°C
GX_13_038
For Training Purposes Only
Sept 04
13-37
P I LOT T R A I N I N G GU I D E
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