User manual

88 89
88 89
Pressurization system
Dukes Pressurization Controller (Cheyenne I & IA)
Garret Pressurization Controller (Cheyenne II & IIXL)
1: Cabin rate of climb gauge 4: Cabin altitude controller
2: Cabin altitude gauge 5: Cabin pressure test/dump
3: Cabin rate of change control switch (Garret only)
Defaults to 500 ft/min cabin
change rate May be adjusted to a minimum of 100 ft/min or a
maximum of 1000 ft/min (Garret: 2500 ft/min)
Pressurization air for the Piper Cheyenne is obtained by use of high
pressure engine compressor bleed air. The high pressure air is routed
through an intercooler, then into a jet pump which mixes bleed
air with outside air. The decreases the amount of high pressure air
required from the engine and also lowers the temperature of the bleed
air. The air then proceeds to the main pressure line under the cabin
floor and passes through the pressurized air control box assembly,
which controls the flow of air that is to be routed either to the cabin
or overboard.
The cabin air control has three positions marked: PRESSURIZED AIR,
RECIRCULATED AIR, and OUTSIDE AIR. When the control is in the
PRESSURIZED AIR position, the air is directed through the air condi-
tioning evaporator to the heater and heater ducts, and through the
cool air ducts along both sides of the cabin to individually controlled