either or both of the bleed air valve switches on the
overhead control panel to PNEU & ENVIRO OFF position
will disengage the rudder boost system.
Condition levers must be in LOW
IDLE position to perform rudder
The system is controlled by a switch
located on the extended pedestal placarded RUDDER
BOOST ON OFF, and is to be turned on before flight. A
preflight check of the system can be performed during the
run-up by retarding the power on one engine to idle and
advancing power on the opposite engine until the power
difference between the engines is great enough to
activate the switch to turn on the rudder boost system.
Movement of the appropriate rudder pedal (left engine
idling, right rudder pedal moves forward) will be noted
when the switch closes, indicating the system is
functioning properly for low engine power on that side.
Repeat the check with opposite power settings to check
for movement of the opposite rudder pedal. The system
is protected by a 5-ampere circuit breaker placarded
RUDDER BOOST, located on the overhead circuit
breaker panel (fig. 2-26).
With brake deice on, rudder boost
may be inoperative.
2-40. FLIGHT CONTROLS LOCK.
towing the aircraft or starting
engines. Serious damage could
result in the steering linkage if
towed by a tug with the rudder lock
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. 2-17) consisting of
two pins, and an elongated U-shaped strap interconnected
by a chain. Installation of the controls lock 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, thus
locking the control wheel. 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.
2-41. TRIM TABS.
Trim tabs are provided for all flight control
surfaces. These tabs are manually activated, and are
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, anti-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.
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. 210). The amount of elevator
tab deflection in degrees from a neutral setting, is
indicated by a position arrow.
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. 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.
Depressing the switch to the first of two levels disconnects
the autopilot and yaw damp system, and the second level
disconnects the electric trim