TM 1-1510-218-10
2-68
Figure 2-23. Control Lock Installation Typical
2-48. TRIM TABS.
Trim tabs are provided for all control surfaces.
These
tabs
are
manually
activated
and
are
mechanically controlled by a cable-drum and jack
screw actuator system, except the right aileron tab,
which is of the fixed bendable type. Elevator and
aileron trim tabs incorporate neutral, non-servo action,
i.e., as the elevators or ailerons are displaced from the
neutral position, the trim tab maintains an "as
adjusted" position. The rudder trim tab incorporates
anti-servo action, i.e., as the rudder is displaced from
the neutral position the trim tab moves in the same
direction as the control surface. This action increases
control pressure as rudder is deflected from the neutral
position.
a. Elevator Trim Tab Control. The elevator
trim tab control wheel, placarded ELEVATOR TAB /
DOWN / UP, is on the left side of the control pedestal
and controls a trim tab on each elevator, Figures 2-7
and 2-9. The amount of elevator tab deflection, in
degrees from a neutral setting, is indicated by a
position arrow.
b. Electric Elevator Trim. The electric elevator
trim system is controlled by an ELEV TRIM PUSH ON
/ PUSH OFF switch located on the pedestal, dual
element thumb switches on the control wheels, a trim
disconnect switch on each control wheel and a circuit
breaker on the overhead circuit breaker panel. The
PUSH ON / PUSH OFF switch must be in the ON
position to operate the system. The dual element
thumb switch is moved forward for trimming nose
down, aft for nose up, and when released returns to
the center (off) position. Any activation of the trim
system through the copilot's trim switch can be
cancelled by activation of the pilot's switch. Operating
the pilot's and copilot's switches in opposing directions
simultaneously results in no trim action. Operating the
pilot’s and copilot’s switches in opposing directions
simultaneously results in the pilot having priority ( D2
T Series only). A preflight check of the switches
should be accomplished before flight by moving the
switches individually on both control wheels. No one
switch alone should operate the system; operation of
elevator trim should occur only by movement of pairs
of switches. The trim system disconnect is a bi-level,
push button, momentary type switch, located on the
outboard grip of each control wheel. Pressing the
switch to the first of two levels disconnects the
autopilot and yaw damp system, and the second level
disconnects the electric trim system. The system can
be reset by pressing the ON / OFF switch on the
pedestal to ON again. The manual trim control wheel
and the electric trim system cannot be used
simultaneously.
c. Aileron Trim Tab Control. The aileron trim
tab control, placarded AILERON TAB LEFT / RIGHT,
is on the control pedestal and will adjust the left aileron
trim tab only. The amount of aileron tab deflection,
from a neutral setting, as indicated by a position arrow,
is relative only and is not in degrees. Full travel of the
tab control moves the trim tab 7½° up and down.
