PNEUMATICS
AIR CONDITIONING
AND PRESSURIZATION
AIRPLANE
OPERATIONS
MANUAL
2-14-05
Page
2
Code
01
REVISION 29
PNEUMATIC SYSTEM
The pneumatic system receives compressed and hot air from the
following sources:
− Engines compression stage
− APU
− Ground pneumatic source
The pneumatic system is used for: engine start, air conditioning,
pressurization and anti-ice system.
Engine bleed air comes from the 9
th
(low pressure) or 14
th
(high
pressure) engine stages depending on the system demand.
The 14
th
stage High Stage Valve (HSV), which is electrically
commanded and pneumatically-actuated, opens automatically during
low engine thrust operations, engine cross bleed start and anti-ice
operation.
As thrust increases, the HSV closes and the 9
th
BACV (Bleed Air
Check Valve) opens supplying bleed air to the system.
Bleed air for engine anti-ice system is provided through the tapping
upstream of the HSV.
An Engine Bleed Valve (EBV), which is electrically commanded
through the Bleed Air Button and pneumatically-actuated, is installed
downstream of the pre-cooler.
Bleed air for the Air Turbine Starter (refer to Section 2-10 - Powerplant)
is provided through the tapping downstream of the EBV.
Each engine supplies air to its corresponding air conditioning pack and
anti-ice system when the respective EBV is open.
During take-off in specific thrust modes using engine bleed air, the
operative air conditioning pack is closed by FADEC's ECS-OFF logic
signal, featuring no engine bleed airflow demand when operating under
no icing condition.
With no engine bleed air demand and high engine's thrust set, for
airplanes Post-Mod. SB 145-36-0028 or equipped with an equivalent
modification factory incorporated, EBV regulates its downstream
pressure in the vicinities of its closed position and then
BLD 1-2 VLV CLSD EICAS advisory message may be displayed for
airplanes equipped with EICAS version 19 and on.
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