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Forward Provides semi-automatic consent. Dispenses flare singles (C/F mode)
Aft Initiates the selected manual program. Dispenses flare singles (C/F mode)
Inboard Initiates manual program 6. Dispenses chaff and flare singles (C/F mode)
Outboard Initiates manual program 6. Dispenses chaff and flare singles (C/F mode)
2.12 ECS - ENVIRONMENTAL CONTROL SYSTEM
The environmental control system (ECS) utilizes engine bleed air, two heat exchangers, and an ECS
compressor/turbine to provide warm air for pressurization and heating and cold conditioned air for
cooling. Warm air is provided for internal and external fuel tank pressurization, canopy seal, g-suit
operation, radar waveguide pressurization, windshield anti-ice and rain removal, gun gas purge,
RECCE bay heating, and on-board oxygen generating system (OBOGS) operation. Cold, dry conditioned
air is provided for avionics cooling. Warm and cold air are mixed to provide temperature
controlled air for cockpit heating, cooling, and pressurization and windshield defog.
A separate liquid cooling system (LCS) is used to cool the radar transmitter. A digital ECS controller
is used to schedule ECS output, regulate system temperatures, monitor system health, and detect and
isolate faults. See foldout section for a schematic of the ECS.
A1-F18EA-NFM-000
I-2-90 ORIGINAL
Items numbers, listed in ( ) next to ECS valves, are maintenance and MSP code nomenclature.
2.12.1 Bleed Air Shutoff Valves. Engine bleed air is tapped from the final (seventh) stage of the
engine high pressure compressor. A primary bleed air pressure regulator and shutoff valve (Item 1), one
on each engine, is used to regulate bleed air output pressure as well as to control flow application/
shutoff.
Both valves are electrically controlled by the BLEED AIR knob and are pneumatically actuated.
The primary bleed air shutoff valves failsafe to the closed position if either electrical power or air
pressure is lost. If an engine is shut down before placing the BLEED AIR knob to OFF, the
corresponding primary bleed air shutoff valve may not fully close, resulting in residual engine fumes
in the cockpit on subsequent start of that engine.
Bleed air from each engine passes through a check valve, which prevents reverse flow, and is mixed
through a Y-junction prior to the secondary bleed air pressure regulator and shutoff valve (Item 2).
This valve is electrically controlled by the OFF and AUG PULL positions of the BLEED AIR knob and
is pneumatically actuated. The secondary bleed air shutoff valve fails to the open (safe) position if
either electrical power or air pressure is lost.
All three valves can be automatically commanded to the closed position by the bleed air leak
detection (BALD) system.
2.12.1.1 BLEED AIR Knob. The BLEED AIR knob, located on the ECS panel on the right console, is
used to select the engine bleed air source for the ECS system.
NORM Commands both primary bleed air shutoff valves open, selecting bleed air from both
engines.
L OFF Commands the left primary bleed air shutoff valve closed, selecting bleed air from the
right engine only.
R OFF Commands the right primary bleed air shutoff valve closed, selecting bleed air from the
left engine only.
OFF Commands all three bleed air shutoff valves closed, isolating the ECS. Closes the ECS
auxiliary duct doors.
AUG
PULL
Commands the secondary bleed air shutoff valve closed, opens the ECS air isolation
valve, and allows APU compressor air to operate the ECS.
2.12.1.2 L or R BLD OFF Cautions. The L or R BLD OFF cautions indicate that the corresponding
primary bleed air shutoff valve(s) are commanded closed. The cautions are not an indication of actual
valve position. The L and/or R BLD OFF cautions are displayed in the following circumstances:
a. BLEED AIR knob in L OFF, R OFF, or OFF (L, R, or both cautions).
b. ENG CRANK switch in L or R (L or R caution, respectively).
c. BALD system detects a leak in one or both bleed air systems (L, R, or both cautions).
d. FIRE switch in TEST A or TEST B (both cautions).
e. Over pressurization in one or both bleed air systems (both cautions).
If a bleed air shutoff valve has been commanded closed other than by ENG CRANK, the BLEED
AIR knob must be cycled to OFF and back to NORM to reopen the valve(s).
A1-F18EA-NFM-000
I-2-91 ORIGINAL
2.12.2 Bleed Air Subsystem. Engine bleed air downstream of the secondary bleed air shutoff valve
is routed to the primary heat exchanger and three valves. The primary heat exchanger is used for first
stage cooling of hot engine bleed air. The ECS air isolation valve directs bleed air to the air turbine
starter control valves (ATSCV) for crossbleed start and accepts air from the APU compressor for
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NATOPS Flight Manual 飞行手册 1(77)
