PART 1-DESCRIPTIVE

    6.   Oil system
        
         An oil tank is fitted in each engine nacelle.   Pre-Derwent
         Mod. 571, each tank has a capacity of 22 pints of oil with
         a 7-pint air space.   Derwent Mod. 571 reduces the oil
         capacity to 19½ pints.
        
    ENGINE CONTROLS                        

    7.   Derwent Mk.8 and 9 engines

   (a)   Both the Derwent Mk.8 and 9 engines are centrifugal-flow
         jet engines giving approximately 3,500 lb. static thrust at
         sea level under I.S.A. conditions.   The Mk.8 engine has
         priming pumps and torch igniters, while in the Mk.9
         engine these are deleted and high energy igniter units are
         introduced.
        
   (b)   The maximum engine r.p.m. are governed at 14,550 at sea
         level; the r.p.m. will increase with altitude to 14,700 r.p.m.
   
    8.   Throttle controls

         Throttle levers mret7pic021.htm
         (12) and (90), are in slides on the port wall
         of both cockpits and, when fully shut (back), sufficient
         fuel is allowed to pass to enable the engines to idle.  No
         friction damping control is fitted.   The throttles must be
         fully closed before the engine starting circuit is complete.  In
         the front cockpit, the port throttle grip incorporates the
         G.G.S. ranging control.   The inboard throttle may carry
         the press-to-transmit switch and a spring loaded mute
         switch.

    9.   Engine starting controls
        
    (a)  The starting cycle is automatically controlled by time
         switches.   When the L.P. pump is on and the throttle closed
         (to operate the micro-switch (7)), pressing and releasing
         the shielded starter pushbuttons (20) on the port shelf
         completes the starting circuit and actuates the time
         switches, which in turn bring the starter motors and igniters
         into circuit.   Current to the starter circuit is automatically
         cut off after 30 seconds.

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