King Air C90GTi, Pilot Training Manual

Page: 271 / 557

CABIN PRESSURE
CONTROL
A n a d j u s t a bl e c a b i n p r e s s u r i z a t i o n c o n -
t r o l l e r ( F i g u r e 1 2 - 8 ) i s m o u n t e d i n t h e
pedestal. It commands modulation of the
outflow valve. A dual-scale indicator dial
is mounted in the center of the pressuriza-
t i o n c o n t r o l l e r. T h e o u t e r s c a l e ( C A B I N
ALT) indicates the cabin pressure altitude
which the pressurization controller is set to
maintain. The inner scale (ACFT ALT) in-
dicates the maximum ambient pressure al-
titude at which the air plane can fly without
causing the cabin pressure altitude to climb
above the value selected on the outer scale
( C A B I N A LT ) o f t h e d i a l . T h e i n d i c a t e d
value on each scale is read opposite the index
m a r k a t t h e f o r wa r d ( t o p ) p o s i t i o n o f t h e
dial. Both scales rotate together when the
c a b i n a l t i t u d e s e l e c t o r k n o b , p l a c a r d e d
CABIN ALT is tur ned.
C a b i n a l t i t u d e i s o b t a i n e d by s e t t i n g t h e
controller to the desired cr uising altitude,
a n d o b s e r v i n g t h e c a b i n a l t i t u d e o n t h e
scale. The maximum cabin altitude selected
may be anywhere from –1,000 to +10,000
feet MSL. The rate control selector knob is
placarded RATE–MIN–MAX. The rate at
which the cabin pressure altitude changes
from the cur rent value to the selected value
is controlled by rotating the rate control se-
l e c t o r k n o b. T h e r a t e o f c h a n g e s e l e c t e d
may be from approximately 200 to approx-
imately 2,000 feet per minute. Nor mal set-
ting on the rate knob will be from 9 o’clock
to 12 o’clock.
T h e a c t u a l c a b i n p r e s s u r e a l t i t u d e ( o u t e r
scale) and cabin differential (inner scale) is
continuously indicated by the cabin altimeter
(Figure 12-9), which is mounted in the right
side of the panel that is located above the
pedestal. Immediately to the left of the cabin
altimeter is the cabin vertical speed (CABIN
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
12-8
FOR TRAINING PURPOSES ONLY
12
PRESSURIZA
TION
Figure 12-9. Cabin Altimeter Figure 12-8. Pressurization Controller