The pneumatic system incorporates overheat,
overpressurization and leak protection through
continuous monitoring and aircrew alerting.
Alerting is through the CAS and CWP systems.
DESCRIPTION AND
OPERATION
LOW-PRESSURE (LP) BLEED-
AIR SYSTEM
Low-pressure bleed air is extracted from the
low-pressure compressor on each engine
(Figure 9-2). The LP bleed-air is ducted from
a port on the inboard side of each engine,
through the pylon and into the tailcone where
it joins in a common manifold with the LP
ducting from the other engine. HP air can be
added to this same manifold through the HP
Shut-Off Valves (SOVs) on an “as-needed”
basis. Check valves are installed within the
ducting to prevent reverse flow from the HP
port into the LP port and from engine to engine.
The LP or the HP bleed-air from each engine
passes through the Environmental Control
System Pressure Regulating Shut-Off Valves
(ECS PRSOVs) on each side in the tailcone
(Figure 9-2). The two engine bleed-air sources
join in the tailcone ducting; then pass through
the PACK BI-LEVEL Pressure Regulating and
Shut-Off Valve (PRSOV) enroute to the
Environmental Control Unit (ECU).
LP bleed-air can also be re-routed directly to
the cabin through emergency pressurization
valves in the event of a disruption in the nor-
mal bleed-air supply. In this case, the normal
bleed-air ducting in the tailcone and the ECU
are by-passed.
Emergency pressurization can be activated
manually by the crew via the EMER PRESS
switch/indicator (S/I) on the Pressurization
control panel (Figure 9-1), or it can be activated
automatically by the Cabin Pressurization
Controller (CPC).
HIGH-PRESSURE (HP) BLEED-
AIR SYSTEM
High-pressure (HP) bleed-air is extracted from
each engine through four outlets on the HP
compressor transition duct (Figure 9-2). Bleed-
air from the four HP outlets is then routed to
a single collector on each engine before being
ducted through the engine pylons to the left and
right HP SOVs in the tailcone.
The HP SOVs are controlled by the dual chan-
nel ECS Controller. During periods of high de-
mand or low supply of LP bleed-air, the HP
SOVs are automatically opened to allow the
HP air to pass through the ECS PRSOVs.
A nacelle anti-ice duct branches off of the HP
supply duct in each engine pylon. These ducts
route HP air to the left and right nacelle anti-
ice valves and on to the nacelle inlet lips when
the L and R NAC switch/indicators are ON
(Figure 9-2).
Just after the HP supply ducts pass from the
pylons into the tailcone, another duct branches
off for Wing and Stab anti-icing. These ducts,
on each side of the tailcone, route HP air to the
left and right Anti-Ice Pressure Regulating
and Shut-Off Valves (A/I PRSOVs). When the
WING/STAB switch/indicator is ON, these
valves are both open, allowing HP air to flow
to piccolo tubes in the leading edge of the
wings and horizontal stabilizer.
AUXILIARY POWER UNIT (APU)
BLEED-AIR SYSTEM
On the ground, the APU (if installed) pro-
v i d e s a n o t h e r s o u r c e o f b l e e d - a i r f o r
cabin/cockpit heating and cooling, APU bleed-
air is ducted into the ECU through the APU
control valve and the Pack Bi-level PRSOV.
These valves are controlled via the PACK and
A P U B L E E D s w i t c h / i n d i c a t o r s o n t h e
Pressurization control panel (Figure 9-1).
9-2
FOR TRAINING PURPOSES ONLY
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
FlightSafety
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