King Air C90GTi, Pilot Training Manual

Page: 256 / 557

MANUAL MODE CONTROL
When the CABIN TEMP MODE selector is
in the MAN HEAT or MAN COOL position,
regulation of the cabin temperature is ac-
complished manually by momentarily hold-
i n g t h e M A N UA L T E M P sw i t c h ( Fi g u r e
11-23) to either the INCR or DECR position
as desired. When released, this switch will
retur n to the center (no change) position.
Moving this switch to the INCR or DECR
position results in modulation of the bypass
valves in the bleed-air lines. Allow approx-
imately 30 seconds per valve (one minute
total time) for the valves to move to the full
heat or full cold position. Only one valve
moves at a time. Movement of these valves
varies the amount of bleed air routed through
the air-to-air heat exchanger. Consequently,
the temperature of the incoming bleed air
will var y. This bleed air mixes with recir-
culated cabin air (which will be air condi-
t i o n e d i f t h e r e f r i g e r a t i o n s y s t e m i s
operating) in the mixing plenum, and is then
ducted to the floor registers. As a result, the
cabin temperature will vary according to the
position of the bypass valves, whether or not
the air conditioner is operating.
When the CABIN TEMP MODE selector is
in the MAN COOL position, the air-condi-
tioning system will operate continuously,
until the system is tur ned off, or until the
evaporator reaches 50°F when the ther mal
sensor tur ns the air conditioning off.
BLEED-AIR CONTROL
Bleed air entering the cabin is controlled by
the two switches (Figure 11-24) placarded
B L E E D A I R VA LV E S – O P E N – C L O S E D.
When the switch is in the OPEN position,
t h e e nv i r o n m e n t a l f l ow c o n t r o l u n i t s a r e
open. When the switch is in the CLOSED po-
sition, the environmental flow control unit
i s c l o s e d . Fo r m a x i m u m c o o l i n g o n t h e
ground, turn the bleed-air valve switches to
the CLOSED position.
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
11-13
FOR TRAINING PURPOSES ONLY
11
AIR
CONDITIONING
Figure 11-23. Manual Temp Switch
Figure 11-24. Bleed Air Valve Switches