King Air C90GTi, Руководство по подготовке пилотов

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f e e t ; a n d 1 2 , 0 0 0 f e e t a t 3 0 , 0 0 0 f e e t .
Although the King Air’s pressure vessel is
designed to withstand a maximum differ-
ential greater than 5.0 psi, the airplane struc-
ture is not designed to withstand a negative
differential.
The pressurization and environmental sys-
tems (Figure 12-1) operate in conjunction
with each other or as separate systems to main-
tain the desired cabin pressure altitude and
cabin air temperature. Occupied compar t-
m e n t s a r e p r e s s u r i z e d, h e a t e d, o r c o o l e d
through a common ducting arrangement.
“Pressure vessel” means that por tion of the
aircraft designed to withstand the pressure
differential. In the King Air, the pressure
vessel extends from a forward pressure bulk-
head, between the cockpit and nose section
to a rear pressure bulkhead, just aft of the
cabin baggage compar tment, with exterior
skins making up the outer seal. Windows are
r o u n d f o r m a x i m u m s t r e n g t h . A l l c a bl e s ,
wire bundles, and plumbing passing through
the pressure vessel boundaries are sealed to
reduce leaks.
AIR DELIVERY SYSTEM
Bleed air from the compressor section of
each engine is utilized to pressurize the pres-
sure vessel. A flow control unit in the na-
celle of each engine controls the flow of the
bleed air and mixes ambient air with it to
provide an air mixture suitable for the pres-
surization function. The mixture flows to the
environmental bleed air shutoff valve, which
is a normally closed solenoid. This solenoid
is controlled by a switch placarded BLEED
A I R
VA LV E S – L E F T ( o r ) R I G H T
OPEN–CLOSED in the ENVIRONMENTAL
controls group (Figure 12-3) on the copilot’s
l e f t s u b p a n e l . W h e n t h i s sw i t c h i s i n t h e
CLOSED position, the solenoid is closed and
no bleed air can enter the flow control unit
or the cabin. When the BLEED AIR VALVE
switch is in the OPEN position, the solenoid
is electrically held open and the air mixture
flows through the valve to the flow control
package. Electricity is required to keep the
flow control solenoid open. If there were a
c o m p l e t e e l e c t r i c a l f a i l u r e , t h e s o l e n o i d
would fail to the closed position. No more
bleed air would enter the pressure vessel and
the cabin pressure would leak out.
The air entering the air plane flows through
the environmental bleed air duct (see Figure
12-1). The air from the environmental bleed
air duct is mixed with recirculated cabin air
(which may or may not be air conditioned) in
the mixing plenum, ducted upward into the
crew heat duct, then routed into the floor out-
let duct. This pressurized air is then intro-
d u c e d i n t o t h e c a b i n t h r o u g h t h e f l o o r
registers. This air may be recirculated through
the air conditioning system. Finally the air
flows out of the pressure vessel through the
outflow valve (Figure 12-4), located on the
aft pressure bulkhead. A silencer on the out-
flow and safety/dump valves (Figure 12-5)
ensures quiet operation.
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
12-4
FOR TRAINING PURPOSES ONLY
12
PRESSURIZA
TION
Figure 12-3. Bleed Air Valves Switches