AIR CONDITIONING AND PRESSURIZATION
Description
Aircraft Operations Manual
2.1
PAGE
3
Jun 01/18
exceeds the ram air pressure keeping the ground
connection check valve closed. Should the remain-
ing ACP fail, ram air pressure opens the check
valve furnishing fresh air to the compartments. The
ram air pressure is adequate to ventilate the
compartments on its own. During cruise a minimum
speed of 210 KIAS must be kept to maintain a suffi-
cient ram air pressure.
Temperature control system (Fig. 1)
Each pack has its own, independent temperature
control system.
The dual temperature control valve can be operated
either automatically to provide a compartment tem-
perature of between 18
C and 29
C, or manually if
necessary. However, in MAN mode, temperature
can be selected within a greater range.
Automatic mode is selected by setting the three
position TEMP SELECT switch in the AIR COND
panel to AUTO. The dual control valve is then oper-
ated by a controller using inputs from temperature
sensors both in the duct and in the respective
compartment. These temperatures are compared to
the temperature selector setting and the control
valves adjust accordingly.
In addition, high and low temperature limit circuits
keep the duct temperature between 3
C (37
F) and
75
C (167
F) at all times.
The dual temperature control valve is manually op-
erated by holding the TEMP SELECT switch in ei-
ther HOT or COLD spring
−
loaded position.
Manual temperature mode shall only be used in
case of failure in the automatic control system (with
Mod. No. 3121 installed the temperature switches
are guarded in AUTO position to prevent unneces-
sary use of the manual mode).
Since the temperature limit circuits are deactivated
in manual mode extreme care shall be taken not to
obtain a temperature below freezing in the distribu-
tion duct. Therefore always keep the recirculating
fan ON for that pack which is operated in manual
mode.
The left distribution duct temperature can easily be
checked on the temperature indicator in the AIR
COND panel.
A temperature below freezing is indicated by snow
blowing through the gaspers or frost freezing in the
gasper nozzles. This situation can block the system
creating an overpressure high enough to damage
the distribution ducting.
Typical operating conditions with manual temp con-
trol when a temperature below 0
C is created in the
distribution ducting.
−
Propeller Brake engaged with:
X
−
VALVE open.
R HP VALVE open (AUTO position).
RECIRC fans OFF.
Dual control valves, TEMP SELECT switches,
max COLD.
−
Normal engine operation with:
Power levers below approximately 80% Ng (HP
VALVES open).
RECIRC fans OFF or ON.
Dual control valves, TEMP SELECT switches,
max COLD.
Optional Pilot footwarmer installation (Fig. 3)
Mod. No. 1345
As an option the cockpit can be provided with foot-
warmers. Air is taken from the normal supply to the
cockpit, the amount of air can be adjusted by an Air
Flow Regulator, one for each pilot. The air temper-
ature is controlled via a heater for each pilot, there-
by providing an individual adjustment for optimum
comfort.
When the footwarmer is used at least one sides
−
BLEED system including the RECIRC FAN must be
ON.
Optional Cockpit floor heaters installation
(Fig. 10) Mod. No. 2293
As an alternate to Mod No 1345, an optional Cock-
pit Floor Heater installation Mod No 2293 can be
provided. Mod No 2293 consists of an electrically
powered heater element embedded in the cockpit
floor carpets. Extent of heater element: see Fig. 10.
On the right pilot side a pull loop is fixed to the floor
carpet close to the hydraulic hand pump position for
easy access.
