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of an isolation valve, air from the bleed air manifold can be directed to
either ECS pack. This results in a constant mass of conditioned air for all
areas within the pressure vessel.
• Control the temperature of conditioned air delivered to the cockpit and
cabin areas (referred to as zones) within the pressure vessel. This is done
using the two ECS packs to cool incoming air and deliver it to a conditioned
air manifold. Valves mix hot bleed air with cold conditioned air to modulate
the temperature of the air coming from the manifold into the pressure
vessel. Water separation, for humidity reduction, is also provided.
During normal inflight operation, temperature-controlled and pressure-controlled
HP bleed air from either or both engines is supplied to the bleed air manifold. Air
from the manifold is provided to the ECS packs, where cooling takes place. Each
pack consists of a primary heat exchanger, secondary heat exchanger and an air
cycle machine (ACM). (The term “air cycle” means that cooling is produced by a
thermodynamic cycle, using only air as a medium, as opposed to a vapor cycle,
which employs Freon™ or other similar gases.) The ECS packs then reduce air
temperature to values above freezing. Humidity reduction is accomplished by a
mechanical water separator.
Temperature control of the zones within the pressure vessel is accomplished by
varying the amount of hot bleed air which bypasses the cooling equipment.
Separate temperature control is provided for the cockpit and cabin zones using a
control panel located on the overhead panel in the cockpit. Provisions for manual
control of the system are included in the event of a failure rendering electronic
control inoperative.
An advantage of the GIV airflow and temperature control system is that it is
capable of functioning independently while on the ground. With the engines not
operating, the bleed air manifold can be supplied with air from either the APU or
from an approved external air cart. System operation on the ground is virtually the
same as in flight, the difference being that ram air flow across the heat
exchangers is provided by a cooling fan.
Should either or both engines be operating, the flight crew may select either or
both engines to supply bleed air to the manifold through use of the ISOLATION
valve switch.
During certain emergency procedures, the flight crew may induce ram air
ventilation into the airflow and temperature control system. Ram air is supplied
from a dorsal fin duct and controlled by a RAM AIR switch located on the
overhead panel in the cockpit.
For the purposes of this description, the airflow and temperature control system is
divided into the following subsystems:
• Air Control System
• Temperature Control System
• Distribution System
• Refrigeration System
• Ram Air Ventilation System
• Temperature Indication System
• Equipment Cooling System
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-21-00
Page 19
May 30/02
Revision 7
2. Description of Subsystems, Units and Components:
A. Air Control System:
(See Figure 6 and Figure 7.)
(1) Bleed Air Manifold:
The bleed air manifold is used as the source of bleed air for the air
conditioning system. Air to the manifold is supplied by either an
approved external air source or APU air (while on the ground), or by
HP turbine bleed air from the aircraft’s engines (on ground or in
flight).
The bleed air manifold delivers air to using systems, one being the
air conditioning system. Delivered air is approximately 400° F at a
maximum pressure of 40 psig. For the air conditioning system, air is
delivered to the air conditioning shutoff and flow regulating valves in
the tail compartment.
(2) Air Conditioning Shutoff and Flow Regulating Valves:
The air conditioning shutoff and flow regulating valves perform two
functions in the air conditioning system:
• Act as shutoff valve when system operation is terminated.
• Act as a flow regulator when the system is operating.
The air conditioning shutoff and flow regulating valve is
pneumatically operated butterfly valve, using upstream duct
pressure as the operating force. An internal electrical solenoid is
installed and, when energized, pressurizes the valve to close it. This
prevents air entry, ending system operation. When de-energized,
upstream duct pressure opens the butterfly valve and airflow starts
again. Airflow through the valve is regulated to a maximum of 42.1
(±1.5) pounds per minute (ppm) of flow.
There are several ways to energize the solenoid and close the
　
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