User manual

Page 48
Aircraft Operation Manual
Piper Cheyenne I, IA, II, IIXL
For ight simulation use only
surized ight or if failures occur in the air-conditioning system. Normal air source
during pressurized ight is provided by engine bleed air through a bleed-air
shutoff valve and bleed-air ducts from each engine.
Bleed air to the ECS is controlled by a pressure regulator/shutoff valve. This valve
can be selected for high and low airow via the ECS SELECT Switch (3). The ECS
SELECT Switch (3) must be in the LO position for engine starting, takoff and lan-
ding. The HI position may be used on the ground to provide maximum heating
or cooling. When in HI Position, an annunciator light labeled HI BLEED ON will
illuminate.
A pressure regulator shutoff valve bypass is installed. This valve supplies a mini-
mum of bleed-air ow to a jet pump which induces air from the raim-air inlet
to mix and supplement bleed-air ow and continues to sustain pressurization.
The ECS bypass valve has a manual and automatic control circuit, controlled by
the ECS REG BYPASS Switch (1). The up position (ON) of the switch will open the
bypass valve and close the pressure regulator/shutoff valve. These two functions
will also occur automatically if either propeller control lever is moved to the fea-
ther position. When the ECS bypass is ON, an annunciator light labeled ECS REG
BYPASS will illuminate. The pressure regulator/shutoff valve will automatically
close if
1. ECS overpressure or
2. ECS overtemperature exceeds the values set by a pressure switch or the
thermal switch sensing temperature
The primary function of the ECS bypass is to reduce engine bleed-air require-
ments to a minimum during engine-out operation. The system should, however,
be manually selected if either an ECS overpressure or overtemperature occurs.
The temperature control system consists of a temperature controller, a mode
switch (2) labeled AUTO and MAN, a temperature selector rheostat knob labeled
COOL and WARM (4), and a MAN TEMP CONT Switch (5) labeled HEAT and COOL.
The MAN TEMP CONT switch (5) is spring-loaded to the center position. When
the mode switch (2) is at AUTO, the temperature controller is armed, and input
from the temperature sensors in the cabin and the temperature selector rheostat
knob is processed to adjust the mixture of hot air with the super cooled air to