from being placed in the OFF position by
a cabin air-conditioning and pressurization system
is shown in figure 4-23.
mistake.
The cockpit switch is a three-position toggle
switch marked ON, OFF, and RAM AIR. When
System Controls
the engine is running and the air-conditioning
The air-conditioning control panel is shown
master switch at NORM, placing the cockpit
in figure 4-24. Three switches and one control
switch to ON engages the air-conditioning and
knob on the panel control the air-conditioning
pressurization system. Placing the switch to ON
operation.
energizes the dual temperature control valve and
opens the cabin bleed air shutoff valve. Depending
on the setting on the automatic temperature
The air-conditioning master switch is a
control thumbwheel, conditioned air flows into
two-position (NORM and OFF) toggle switch,
the cockpit. When the cockpit switch goes to the
guarded to the NORM position. When the switch
OFF position, the cabin bleed air shutoff valve
is in NORM, the main bleed air shutoff valves
opens if the engine is providing air at 8 PSI or
closes and drives the dual temperature control
valve to the full hot position. This prevents any
more. Also the air-conditioning caution light will
airflow to the cockpit. The RAM AIR position
go to off. Hot engine bleed air is now available
closes the cabin bleed air shutoff valve and drives
for operation of the various environmental
the dual temperature control valve to the full hot
systems. Placing the switch in the OFF posi-
tion closes the shutoff valve, thus shutting
position. You now control the ram air flow
manually using the MAN/RAM AIR switch.
off hot engine bleed air to the environmental
system. A spring-loaded guard over the air-
T h e MAN/RAM AIR switch is a four-
conditioning master switch prevents the switch
position toggle switch marked AUTO, HOLD,
COLD, and HOT. The AUTO position enables
the dual temperature control valve to accept
inputs from the automatic temperature control
thumbwheel. Place the switch to HOLD when the
dual temperature control valve is removed from
automatic control. The switch is spring loaded to
HOLD when not in AUTO. Momentarily holding
the switch in COLD or HOT alters the positions
of the hot and cold sides of the dual temperature
control valve to change the cockpit air tempera-
ture. Upon releasing the switch, it springs back
to HOLD, and the dual temperature control valve
remains fixed. The COLD and HOT positions
should be toggled intermittently to avoid
overshooting the desired temperature. With the
selection of RAM AIR on the air-conditioning
cockpit switch, you manually control airflow by
using the RAM AIR switch. The RAM AIR
switch opens and closes the ram air valve.
The automatic temperature control thumb-
wheel enables the crew to adjust the cockpit air
temperature. With the air-conditioning controls
appropriately positioned, you can move the
thumbwheel to any setting between 0 and 14.
Rotating the thumbwheel automatically regulates
the openings of the hot and cold sides of the dual
temperature control valve, thus varying the
cockpit air temperature. You can select a
temperature within a range of 60F to 80F.
Figure 4-24.-Temperature control panel.
