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A.L.1                      PART I - DESCRIPTIVE
Page 14
           (c)  Should the proportioner rotor jam, fuel by-passes the proportioner
                 vane pumps via by-passes which contain spring-loaded non-return
           (d)  Unequal feeding is only likely to occur if inlet pressures to the pro-
                 portioner differ by more than 2 lb./sq. in., the greater pressure
                 difference, the greater the amount of unequal feeding.

           7.   Low pressure fuel cock    
           (a) The L.P. fuel cock control (14) is on the port shelf and moves forward
           from OFF to ON.  It controls the fuel flow to the engine.
           8.   Filter de-icing    
           (a) Since fuel contains a small amount of moisture an automatic de-icing
               system is fitted to ensure that the fuel filter is not blocked by ice
               crystals at low O.A.T.'s.  When icing occurs an electric pump is
               switched on and pumps alcohol to the filter  It is brought into use by
               the increasing pressure drop through the filter.  When the pressure
               drop returns to normal, the system is switched off.
           (b) The de-icing fluid tank, of one gallon capacity, is mounted in the
               engine bay.
           8A.   Rear tank explosion suppression system (Mod. 582)    
           (a) General
                 (i) The explosion suppression system provides an automatic means
                     of suppressing an incipient explosion within a fuel tank.  An explo-
                     sion is not instantaneous but requires a measurable time from the
                     moment of ignition to the development of maximum pressure of
                     a destructive nature.  In the initial stages the rate of pressure
                     increase is comparatively slow and hence can be suppressed in
                     this period.
                 (ii)The basic components of the explosion suppression system are :-
                          A detector unit
                          A suppressor unit.
                          A power pack

            (b) Detection unit
                  In each rear tank is a highly sensitive photo-electric cell, a
                  detonator firing unit and a suppressor unit.  The presence of any light
                  within a fuel tank, such as the initial ignition leading to explosion
                  causes the photo-electric cell to pass current to the detonator firing

            (c) Suppressor unit           
                  (i)  When the detonator firing unit operates it causes a detonator
                       in the centre of the suppressor unit to fire. This bursts the outer
                       casing of the suppressor unit to release the suppressant agent.
                       As the suppressor unit casing is suitably scored the metal remains 
                       attached to the unit after bursting and no large particles of metal
                       are discharged into the tank.
                  (ii) The suppressant agent is primarily a fuel with a small quantity
                       of extinguishant  When this mixture is released it has the effect
                       of enriching the fuel/air vapour to a non-explosive ratio, thus
                       terminating the explosion and halting the attendant pressure
                  (iii)Permanent indication that a unit has fired is given by a match-
                       head fuse within a viewing window at each tank.  When a unit
                       fires, the fuse operates to ignite the match-head and to disperse
                       red oxide over the viewing window.


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