PART I - DESCRIPTIVE

                reading of the triple pressure gauge main needle.  The
                audio warning cut-off switch (60) on the starboard side
                of the instrument panel enables the noise to be silenced
                once the warning has been given.
                
           (e)  Two high pressure air bottles which are charged to
                1,800-2,000 lb./sq. in., are provided for the emergency
                lowering of the undercarriage and flaps respectively.  Air
                pressure gauges (6) (7) for the bottles are mounted on
                the port shelf.
                
           (f)  A hydraulic handpump, for ground test purposes, is
                fitted in the engine bay.
           
           POWERED FLYING CONTROLS AND
                TRIMMERS

           20.  Flying controls operation 
           
           (a)  In power
           
                The ailerons and elevators are power-operated, the power
                being supplied by hydraulic oil under pressure from the
                aircraft hydraulic system.  A hydrobooster consisting of
                a valve and jack body and jack piston is fitted close to
                each control surface.  The control column is connected
                direct to the valve control rod so that, depending on the
                direction of movement of the control column, the valve
                opens to admit pressure oil to one side of the jack
                piston and at the same time the other side is opened to
                return.  The piston rod is anchored to the aircraft
                structure by means of spring-loaded hydraulically-
                operated pawl.  The jack body is directly connected to
                one end of the control surface.  When the pawl is in
                position and hydraulic pressure is fed from the valve to
                one side of the jack piston, the jack body moves relative
                to the piston and deflects the control surface.  When
                control column movement ceases, the valve closes
                causing a hydraulic lock which prohibits further move-
                ment of the jack body and control surface.

24