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provides crossbleed capability during single engine operations to enable
engine starting and cranking using the opposite side’s pneumatic system,
as well as APU bleed air. The bleed air isolation valve receives power from
the Essential 115V AC bus (φA) through the BLEED AIR ISO S/O V circuit
breaker.
During normal operations, the isolation valve is closed and the left and right
side pneumatic systems are isolated from each other. Manual selection of
the ISOLATION switch (cockpit overhead panel, BLEED AIR section)
opens the isolation valve. A “bar” in the switch illuminates to fill in the
crossover manifold line engraved on the BLEED AIR panel, signifying that
the left and right side pneumatic systems are no longer isolated. In addition
to the switch legend, a blue ISOLATION VLV OPEN advisory message is
displayed on CAS. With the isolation valve open, crossbleed air and APU
bleed air are available to both pneumatic systems for use by both
refrigeration packs and for engine starting as required.
In addition to manual control, the bleed air isolation valve is capable of
automatic control while the airplane is on the ground by certain bleed air
configurations. If the isolation valve is closed, selection of APU BLEED AIR
to ON or selection of either the MASTER CRANK or MASTER START
switches to ON will automatically open the isolation valve. When APU
BLEED AIR is selected off or the MASTER CRANK or MASTER START
switches are selected off, the isolation valve will automatically close.
A manual override slot drive is provided on the valve itself so that the valve
can be positioned with a screwdriver without the need for electrical power.
The slot drive is connected to a common shaft, ensuring the
synchronization of internal limit switches with valve position at all times
regardless of whether the valve is actuated electrically or manually.
On airplanes SN 1445 and subsequent and SN 1000-1444 with ASC 422A,
the existing bleed air system wiring is modified to provide an annunciation
for an incorrect bleed air configuration. This annunciation serves to caution
the flight crew to the possibility of engine overtemperature if the isolation
valve is open while the APU and/or engine bleed air switches are set to
certain positions while on the ground. On SPZ-8400 equipped airplanes, an
amber BLEED CONFIG caution message is displayed on CAS. On SPZ-
8000 equipped airplanes, an amber BLEED CONFIG light illuminates
above each navigation display. See Figure 5. After a five second delay,
display of the annunciation is prompted when:
• Both ENG BLEED AIR switches are selected ON (OFF legend
extinguished) with the isolation valve OPEN, or:
• Either or both ENG BLEED AIR switches are selected ON and APU
BLEED AIR is selected ON (isolation valve opens automatically), or:
• Any two of the three available bleed sources (L ENG, R ENG and/or
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-36-00
Page 7
October 11/02
Revision 8
APU) are selected ON and either the MASTER CRANK or MASTER
START switch is selected ON (isolation valve opens automatically)
NOTE:
To incorporate ASC 422A on SPZ-8000 equipped
airplanes, ASCs 327, 327A, 327B and any associated
amendments must first be incorporated.
G. APU Bleed Air Distribution:
The APU bleed air duct is connected to the right side of the bleed air
manifold. Selection of the APU BLEED AIR switch (cockpit overhead panel,
BLEED AIR section) to ON opens the APU’s load control valve and the
isolation valve. The ON legend in the switch illuminates. APU bleed air then
flows through a check valve in the APU bleed air duct into the bleed air
manifold. Should bleed air manifold pressure exceed APU bleed air
pressure, the check valve in the APU bleed air duct will close to prevent
reverse flow.
APU bleed air is inhibited while airborne. Only electrical power is available
from the APU.
H. External Air Distribution:
(See Figure 9.)
The external air duct is connected to the left side of the bleed air manifold.
On the opposite end of the duct is a coupling where the external air cart is
connected. The external air connection point is located in the underside of
the fuselage, just forward of the hydraulic system service access door. With
the proper external air cart connected, the flight crew may use external air
as required for engine starting. Should bleed air manifold pressure exceed
external air duct pressure, a check valve installed in the external air duct
will close to prevent reverse flow.
I. Door Seal Pressure Distribution:
(See Figure 1, Figure 3 and Figure 6 through Figure 8.)
　
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