AIR CONDITIONING SYSTEM

AIR CONDITIONING SYSTEM
1. Cabin/Cockpit air conditioning is provided by a vapor-cycle refrigeration system.

The compressor, driven by the right engine, will operate as required in the AUTO or
MAN COOL control modes, provided operation is not prohibited by the system
protection controls. System protection controls will prevent compressor operation if
refrigerant pressure is too high or too low, if the bleed air bypass valve has reached a
limit switch (indicating significant heat is being introduced), or if right engine is below
62% N1. If operation is prevented due to low N1 speed, the Air Cond N1 Low CAS
message will be displayed.
2. The cockpit blower assembly recirculates cockpit air through the forward
evaporator and into the 4 cockpit distribution ducts which supply glareshield outlets and
windshield defrost. Two cabin blower assemblies provide cooling to the main cabin by
recirculating cabin air through two evaporators and into ducting which supplies the 9
eyeball air outlets in the cabin headliner, and the 2 eyeball air outlets in the cockpit
headliner.
3. Environmental controls. The environmental control section on the copilot’s left
subpanel provides for automatic or manual control of the system. The system is a dual
zone design, allowing for independent control to the temperature in the cabin and
cockpit.
4. Automatic control mode. When the MODE selector switch is set to the AUTO
position, the heating and air conditioning systems operate automatically. The system
will automatically adjust blowers speed, bleed air temperature and compressor clutch
on/off state to maintain the temperature set points selected via the TEMP knobs. The
recommended temperature setting is straight up at the 12 o’clock position which
equates to approximately 75F. In addition, the controller will modulate 4 servo-
operated airflow valves in the bleed air heat ducting that direct bleed air into the various
sections of the airplane on an “on demand” basis in order to help maintain the desired
temperature setpoints. When there is little or no demand for bleed air heat in the cabin
or cockpit, the majority of the conditioned bleed air is directed aft to the baggage
compartment. Temperature sensing devices in the cockpit and cabin, in conjunction with
the TEMP settings, signal the controller to make the necessary adjustments to maintain
the set point temperature. If at any time the operator wishes to manually select a
different blower speed, the BLOWER control can be rotated out of the AUTO detent to
the desired speed. User patience should be practiced with the temperature control set
point. The controller will maintain set point over time. This slow transition is purposefully
built-in to eliminate unwanted temperature variations.
5. Manual mode control. When the MODE selector is set to the MAN HEAT
position, the Cockpit and Cabin floor heat servos are fully opened and regulation of the
cabin and cockpit temperatures is accomplished by actuating the MAN TEMP switch to
either the INCR or DECR position as desired. When released, this switch will return to
the center (no change) position. This regulates the temperature of the bleed air entering
the airplane, while the flow rate remains unchanged. Bleed air temperature response is
proportional to the length of time the MAN TEMP switch is actuated with approximately
30 seconds required to go from full increase to full decrease or vice versa, Actuations
should be 2-3 seconds in duration with approximately 60 seconds in between to avoid
temperature over/undershoots. Longer than 2-3 second switch actuations and shorter
than 60 seconds in between may result in a duct overheat situation. Refer to the DUCT
OVERTEMPERATURE procedure in Section 3A, ABNORMAL PROCEDURES if this
occurs.
6. The cockpit temp control knob can then be used to manually select the
temperature of the glareshield and windshield defrost outlets. The CABIN TEMP control
works similarly. When the TEMP control is rotated to full counterclockwise (CCW), the
air out of the cabin and cockpit overhead outlets is the coolest (recirculated air without
added bleed air heat). The CABIN and COCKPIT BLOWER controls can be used in this
mode to control the amount of recirculated air coming out of the appropriate outlets for
air recirculation.
7. When the MODE selector switch is set to the MAN COOL position, the air
conditioner system will operate, provided the speed of the right engine is above 62%
N1, and the system pressures are within range. To prevent the evaporator coils from
freezing, the blowers will default to a preset minimum speed. In this mode, the TEMP
setting knobs operate the same as in MAN HEAT and blower speed can be changed by
varying the CABIN and COCKPIT BLOWER controls. In either manual modes, it is the
responsibility of the pilot to actively monitor the temperature and flow of the bleed air
entering the cabin.
8. Electric heat mode control. When the MODE selector switch is set to the ELEC
HEAT position, air is directed over resistive heater elements and into the cabin as
described above under the ELECTRIC HEATING section. This mode is only operative
on the ground.
9. COCKPIT and CABIN BLOWER speed may be manually adjusted to obtain the
desired amount of flow exiting the outlets for air recirculation in any mode except ELEC
HEAT, where the cockpit blower defaults to a high setting. When the blower switches
are in the AUTO detent (full CCW), and the Environmental Mode control is in AUTO,
blower speed will be adjusted automatically by the controller. When predominantly
cooling the cockpit/cabin, the further the actual cockpit/cabin temperature is away from
the selected setpoint, the higher the blower speed will be. As the actual temperature
approaches the setpoint temperature, the controller will begin to reduce the blower
speed until the setpoint temperature is achieved. At this point the blower speed will be
maintained at a default minimum speed. When predominantly heating the cockpit/cabin,
the blower will default to a minimum speed.

AIR CONDITIONING SYSTEM - 40 Mins

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1. Cabin/Cockpit air conditioning is provided by a vapor-cycle refrigeration system.

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