Eagle ICA-D212-725, Instructions Manual

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ICA-D212-725 (21
)
Page 7 of 14
CHAPTER 21 – AIR DISTRIBUTION (VENTILATION) (21-00-00)

COPYRIGHT

2007 BY DART AEROSPACE LTD.

THIS DOCUMENT IS PRIVATE AND CONFIDENTIAL AND IS SUPPLIED ON THE EXPRESS CONDITION THAT IT IS NOT TO BE USED FOR ANY PURPOSE OR COPIED OR COMMUNICATED TO ANY
OTHER PERSON WITHOUT WRITTEN PERMISSION FROM DART AEROSPACE LTD.
Revision:
4
Date: 11.06.01
21.3 BLEED AIR HEATING SYSTEM
COMPONENTS
The following paragraphs provide maintenance
information for various miscellaneous
components. These procedures are typical for all
serial number helicopters. Minor differences may
exist due to helicopter configuration and various
kits which may be installed.
21.4 BLEED AIR SWITCH
The bleed air switch is located adjacent to the
copilot’s collective lever jackshaft. It serves to
stop bleed air flow from the engine to the heater
system when maximum engine power may be
required for flight. The switch is activated when
the collective is raised approximately 12.5 to 13.5
degrees from the full down position. When the
switch is activated, an overheat condition is
simulated electrically and bleed air is shut off at
the variable control mixing valve. When the
collective pitch lever is lowered, normal bleed air
heating is resumed. (Refer to Chapter 96.12.10,
Rigging - Bleed Air Priority Switch, for bleed air
switch rigging procedures.)
Note: refer to Chapter 95, for information
regarding BLEED AIR OFF lights.
21.5 VARIABLE CONTROL MIXING VALVE
The mixing valve (5, Figure 21-2 and 21-3) is
installed on the right side below the engine deck.
This valve controls bleed air and ambient air flow as
directed by the remote sensor (18). A bleed air
nozzle inside the mixing valve acts as a jet pump
through a venturi to draw in ambient air and control
the mixed air flow. When heated air is not at the
selected temperature, the remote sensor causes the
variable control mixing valve to increase or decrease
engine bleed air flow and to regulate ambient air
flow as required to correct the temperature variation.
A temperature limit switch (6) is located on the
mixing valve to protect the structure from damage if
a distribution system duct ruptures. This switch is set
at 220°F (104°C). II this temperature is exceeded,
the CABIN HTR circuit breaker will open.
21.5.1 Removal
21.5.1.1
Open access door at rear of fuselage
under engine compartment to gain access to heater
compartment.
21.5.1.2
Remove two sensing lines, on-off valve
wiring and overheat temperature switch (6, Figure
21-2 or Figure 21-3) wiring.
21.5.1.3
Disconnect tube, remove clamp, large B
nut and attaching hardware and remove valve (5).