PART I-DESCRIPTIVE

          on the port wall. A temperature indicator (19) on the
          port shelf registers whenever the master switch is ON
          and electrical power is available.

     (b)  When the master switch is ON, air is bled from the
          engine compressor and fed to three entry points in the
          cockpit. One at the extreme rear end of the port shelf
          can be blanked off at will: the same feed line supplies air
          to a small louvre (44) on the port side of the instrument
          panel. The quantity of air entering the cockpit via this
          louvre will depend on whether the inlet port is blanked
          off or not. The third entry point is a larger louvre (78)
          on the starboard wall, above the oxygen regulator.

     (c)  The cockpit pressure control valve limits the pressure
          differential to 3½ lb./sq. in. at 27,000 ft. and above. If
          the pressure differential falls below a predetermined
          minimum, a warning light (53) on the instrument panel
          comes on. Should the differential fall still further a
          warning horn sounds. The horn may be silenced by the
          operation of a guarded switch (76) on the starboard wall.
          An altimeter (68) which shows the equivalent cockpit
          altitude is on the starboard shelf.

     (d)  A manually operated vent (7) on the port wall
          admits air at atmospheric pressure, and may be opened
          when the pressurization system is OFF or to release
          pressure in an emergency.

     (e)  The hood seal and the cartridge starter access door seal
          are inflated by air direct from the engine compressor.
          
           
     35.  Hood and windscreen de-misting

     (a)  Hot air for de-misting the windscreen interspace is fed
          direct from the engine compressor.
          
     (b)  Hot air supply to the windscreen and hood gallery pipes
          is controlled by a DEMIST switch (12) on the port wall.
          The air supplied is very hot at high power and low
          altitude and in these circumstances should only be used
          if mist has already formed. It should be used at high
          altitude and, to reduce the possibility of mist forming.
          it should be left on for the descent.

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