Cessna 172 Training Manual page 3

CESSNA 172 TRAINING MANUAL
trim wheel will trim nose-down, conversely, aft (down) rotation will trim nose-
up. The trim tab control wheel depending on the model may be mounted on the
centre console or in the cockpit floor. A portion of the wheel extends through the
control wheel cover and when rotated, operates the tab through roller chains,
cables, an actuator, and a push-pull rod. A position indicator at the trim tab
control wheel indicates nose attitude of the aircraft.
A rudder trim system
is installed in later
models to provide a
means of directional
trim. The
system increases
directional stability
and is especially
useful during climb-
out operations
when the engine is
operating at nearly
full power and the
aircraft forward speed
is
relatively low. The
trim compensates for
engine torque by
applying slight rudder
control in
the direction
necessary for
maintaining straight
forward flight. During
Illustration 3f Trim Connections
cruise, the rudder
trim may be adjusted to maintain balance for any power setting and airspeed.
The rudder trim, if installed, is operated by either a rudder trim control tab or
control wheel mounted on the centre control pedestal.
With a rudder trim control wheel, rotation of the control wheel to the right
provides "NOSE RIGHT" trim, and left rotation provides "NOSE LEFT" trim. A
rudder trim position indicator indicates the trim setting when the trim control
wheel is adjusted.
With a trim lever, trimming is accomplished by lifting the trim lever up to clear a
detent, then moving it either left or right to desired trim position (as shown in
the picture below). Moving the trim to the right will trim nose-right, conversely,
moving the lever to the left will trim nose-left.
The rudder trim control is connected via a bell crank to a bungee, which is
directly connected to the rudder pedal control bar and thus to the rudder itself.
by D. Bruckert & O. Roud © 2006 31