Acu Valves - BOMBARDIER Challenger 601-3A CL-600-2B16 Pilot Training Manual

ACU VALVES

Each ACU has a dual-pressure regulating and
shutoff valve controlled through separate ACU
switch-lights labeled "L" and "R" on the bleed-
air control panel (Figure 11-2). Each ACU valve
requires electrical power and pneumatic pressure
for operation. The electrical power is supplied
from DC bus 1 and DC bus 2, respectively.
TEMPERATURE CONTROL
COCKPIT
STANDBY
NORMAL MAN
40 CABIN
TEMP
20
°C
0
-20
TEMP
Figure 11-2. Bleed-Air Panel
Each ACU valve operates automatically in ei-
ther high or low modes. For example, the ACU
valves operate in a high mode on the ground
if the pneumatic source is the APU. This is to
ensure sufficient cooling air across the heat ex-
changers to compensate for the absence of
ram-air cooling. This ground airflow is in-
duced by ejectors in the ram-air ducts. The
ACU valves will also operate in a high mode
in flight if one ACU is selected off.
Each ACU switchlight has a split legend which
illuminates as a white "OFF" or as an amber
"FAIL." When both appropriate DC power
and pneumatic pressure are available, pushing
an ACU switchlight will cause the OFF light
to extinguish and the valve to open. During op-
eration, with the ACU valve open, if pressure
in an ACU exceeds the design limit, the ACU
valve will try to automatically close and the
amber FAIL legend in the switchlight will il-
luminate. Because this overpressure condi-
tion could be caused by a faulty valve, the
associated left or right engine bleed-air valve
and the isolation valve (if open) will close at
the same time. The BLEED CLOSED light
will illuminate for the affected engine BLEED
11-4 CL 601-3A
CABIN
STANDBY
NORMAL MAN
-40
TEMP
FOR TRAINING PURPOSES ONLY
FlightSafety Canada
CL-600-2B16 PILOT TRAINING MANUAL
AIR switchlight and the OPEN light for the
ISOL switchlight will extinguish.
If a problem is caused by overtemperature in
the ACU, the affected ACU regulating and
shutoff valve will close and only the ACU
amber FAIL light will illuminate. The engine
bleed-air valve and isolation valve (if open)
will remain open.
To prevent damage to the ACU, if the pressure-
regulating and shutoff valve fails to close
when the ACU is deselected, an ACU FAIL
light will illuminate.
In either case, the serviceable ACU will au-
tomatically go to high mode.
DISTRIBUTION
Air distribution to the occupied areas is achieved
by a ducting system (Figure 11-3) on the right
and left sides of the cabin and cockpit. Cold air
ducts using adjustable gasper-type outlets are
located above each passenger seat, on the cock-
pit overhead panel. The cold air duct is ex-
tended behind the instrument panels to provide
for instrument cooling. Separate ducting from
the bleed-air crossover manifold is used for
the footwarmer and demisting system. This is
not conditioned air and is discussed in Chapter
9, "Pneumatics." Cabin air exhaust is vented to
the underfloor area, while cockpit air is ex-
hausted to under the cockpit area for avionics
cooling. All exhaust air from the occupied areas
flows aft to the pressurization outflow valves
in the rear pressure bulkhead.
OPERATION
GENERAL
During the prestart checklist, the APU is started,
and after stabilizing at 100% rpm, the APU
bleed system is available for use. The cabin
and cockpit mode selectors (see Figure 11-1)
are set at NORMAL and the temperature s-
L t é e
L t d .