Figure 2-21. Controls Lock
2-38. FLIGHT CONTROLS LOCK.
Remove control locks before towing
the aircraft or starting engines.
Serious dam- age could result in the
steering linkage if towed by a tug
with the rudder lock installed.
Positive locking of the rudder, elevator and aileron
control surfaces, and engine controls (power levers,
propeller levers, and condition levers) is provided by a
removable lock assembly (fig. 2-21) consisting of two
pins, and an elongated U-shaped strap interconnected
by a chain. Installation of the control locks is
accomplished by inserting the U-shaped strap around
the aligned control levers from the 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. The rudder is held in a neutral position by an
L-shaped pin which is installed through a guide hole in
the floor aft of the pilots rudder pedals. 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.
2-39. TRIM TABS.
Trim tabs are provided for all flight control
surfaces. These tabs are manually activated, and
mechanically controlled by a cable-drum and jackscrew
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 (fig. 2-11). The
amount of elevator tab deflection, in units 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 - OFF/
RESET switch located in the pedestal, dual element