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. 30
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