PART 1-DESCRIPTIVE
moved towards HOT the hot air valve opens
further and the cold air valve closes.
HOT Cold air valve 'shut, hot air valve fully open.
REDUCE Cold air valve shut, hot air valve partially
open. The temperature of the incoming air
remains the same, but since its volume is
reduced the overall cockpit temperature is
thus reduced.
(b) With the wheel set other than OFF pressurised air is
admitted to the cockpit through gallery pipes round the
lower edges of the hood and windscreen. The quantity
of warm air entering the gallery pipes, which provide for
windscreen and hood demisting, can be varied by altering
the position of two ventilators (63) in the shape of rotatable
sleeves, one on each wall of the cockpit. A valve in the
cockpit allows a steady increase in pressure differential
at heights above 12,000 ft., increasing with altitude until
at 35,000 ft. the full pressure differential of 3 lb./sq. in.
is reached. At this height the cockpit altimeter (25)
should read 21,000 ft. A CABIN PRESS LOW
warning light (26) comes on whenever the pressure falls
substantially below the correct figure.
(c) If a reduction of cockpit temperature is desired at altitude,
MIX is to be preferred to REDUCE otherwise the
reduced volume of air entering the cockpit may adversely
affect the pressure differential. COLD or MIX must not
be selected on the ground otherwise overheating of the
cold air unit may occur with subsequent damage.
30. Windscreen de-icing, windscreen wiper and d/v, panels
(a) The W'SCREEN DE-ICER PUMP control (55) is
above the Ground/Flight switch. The handle is turned
anti-clockwise to unlock and pushed in to raise pressure.
As the handle returns to the out position, the windscreen
is sprayed.
(b) Two d/v panels are fitted, one on each side of the main
A.L.1 windscreen. Each is locked shut by a sliding bolt, and
screw clamp.
(c) The hydraulically-operated windscreen wiper for the port
windscreen is controlled by an ON-OFF-PARK knob
(13) below the port instrument panel.
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