TM 55-1510-221-10
APOO5445
Figure 2- 18. Control Locks
copilot’s side; then the aileron/elevator locking pin
is inserted through a guide hole in the top of the
pilot’s control column assembly, thus locking the
control wheel. The rudder is held in a neutral posi-
tion by an L-shaped pin which is installed through
a guide hole in the floor aft of the pilots rudder ped-
als. The rudder pedals must be centered to align the
hole in the rudder bellcrank with the guide hole in
the floor. Remove the locks in reverse order, i.e.,
rudder pin, control column pin, and power control
clamp.
2-40. TRIM TABS.
Trim tabs are provided for all flight control sur-
faces. 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 incorpo-
rates anti-servo action, i.e., as the rudder is dis-
placed 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 pedes-
tal and controls a trim tab on each elevator (fig.
2-7). The amount of elevator tab deflection, in
degrees from a neutral setting, is indicated by a posi-
tion arrow.
b. Electric Elevator Trim. The electric eleva-
tor trim system is controlled by an ELEV TRIM -
ON - OFF/RESET 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 ON - OFF/RESET switch must be in the
ON position to operate the system. The dual ele-
ment 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 over ridden by activation of the pilot’s
switch. Operating the pilot’s and copilot’s switches
in opposing directions simultaneously results in the
pilot having priority.
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 eleva-
2-37
