PART 1-DESCRIPTIVE

   (c)  After a period of 30-40 seconds the time switch cuts
 	off the starting circuit and the engine accelerates under
 	its own power to idling r.p.m. 3,000±200.
                                             

   12.  Engine relighting system

        A pushbutton (4) is incorporated in the end of the H.P. 
        cock lever.   It should be pressed to energise the igniter
        plugs when relighting in flight.   It may also be used as
        an audible check that the H.E. ignition is functioning.
        The relight system will operate irrespective of the engine
        starter master switch.

 	        
   13.  H.P. pump isolating valve
   
   (a)  The output of the H.P. pump is monitored by the B.P.C.
        through the pump servo system.   A solenoid-operated
        isolating valve is fitted to enable the pump to be isolated
        from the servo system.   When the FUEL PUMP
        ISOLATING SWITCH (48) adjacent to the booster
        pump switch is on, the valve isolates the H.P. pump from
        the servo system and the pump then moves to full stroke
        and is controlled by the pump overspeed governor
        and by the throttle position.

   (b)  The isolating valve is primarily intended as a means of
        restoring power in flight if failure of the servo system
        causes a sudden drop in engine r.p.m.   It may also be
        used as a safeguard against failure of the system during
        take-off, if desired.   It must be switched OFF as soon as
        a safe height is reached, otherwise overfuelling will occur,
        resulting in rising j.p.t. and increasing r.p.m. as height
        is gained.
        
        NOTE:-If failure of the servo system occurs whilst
              isolated there is a probability of fuel starvation
              leading to flame-out when the switch is returned
              to OFF.

 	        
   14.  Engine fire-extinguisher

   (a)  The combined fire-extinguisher pushbutton (29) and
        engine FIRE warning light is on the right of the upper
        panel above the flap position indicator.   When Mod.
        3471 is incorporated a second red light (28) is positioned

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