PART I-DESCRIPTIVE

     22.  Elevator feel and trim

     (a)  On the elevator the piston rod is anchored to the control
          circuit itself, to that approximately 1/15th of the air loads
          on the control surface are fed back to the stick, and
          changes of air load on the elevator will be felt by the pilot
          as changes of stick force, thus providing a measure of
          control feel.

     (b)  (i)  The variable incidence tailplane is provided to trim
               out the changes of stick force with speed.  After
               selecting by feel the required tailplane angle to give
               zero stick force for a given flight condition, the
               elevator is trailing with no air load imposed on it.

         (ii)  The tailplane is operated by two electric motors
               controlled normally by a spring-loaded three-
               position switch (69) on the control column hand
               grip.  A speed control snitch (8) on the port shelf is
               provided for FAST or SLOW operation. When set 
               to FAST the tailplane is operated by both motors:
               when set to SLOW only one motor (the starboard port) A.L.1
               operates and tailplane movement is about half the
               fast rate.

        (iii)  A DUPLICATE SLOW CONTROL switch (16) on
               the port shelf can be used to operate the tailplane
               on the port motor only, regardless of the setting of
               the FAST SLOW switch. When the duplicate switch
               is in use the control column switch is inoperative.

         (iv)  If any fault develops in the control column switch
               leading to a "runaway" tailplane, the switch may
               be isolated by means of the MAIN TRIM
               ISOLATION switch (15) on the port shelf and
               trimming achieved by means of the DUPLICATE
               SLOW CONTROL.

          (v)  A.T.P. INCIDENCE PRESELECTOR lever (29)
               inboard of the throttle, when set forward permits
               operation of the tail within a + 4° to - 4° range.
               When set aft the negative limit is increased to -9°.
               The lever must only be moved to the - 9° position
               when the tail is clear of the -4° limit stop.

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