Cessna 150 Series Service Manual page 231

7. RUDDER AND ELEVATORS.
a. With the rudder/elevator set upon a FLAT, LEVELED surface, block up the trailing edge
until a center line through the attaching bolt and the trailing edge is equal distance from the
leveling surface (detail H).
b. Place the balancing beam (detail A) on the rudder/elevator near the center attaching bracket,
(90
°
to the hinge line). Adjust the trailing edge support on the balancing beam (detail H) until
the beam is level. If the rudder/elevator has not been disturbed during this operation, the
beam is now parallel to the chord line of the rudder/elevator.
NOTE
The above procedure must be performed with care. Small angular
discrepancies will produce large balancing errors.
c. Mark position of the balancing beam, then remove and balance the beam by itself at the knife
edges by adding washers as shown in (detail C).
d. Place the balancing beam on the rudder/elevator in its original position, then remove the block
from beneath the trailing edge.
e. Place the sliding weight (detail H) on the forward end of the balance beam, move it along the
beam until the beam is again level.
A small, lightweight, spirit-level may be used for this
purpose provided it is symmetrical about its bubble reference and this reference is placed
on the beam directly over the rudder/elevator hinge line (detail H).
f. If the rudder/elevator is correctly balanced, the position of the sliding weight with respect to
the rudder/elevator hinge line, will produce a moment about the hinge line somewhere within
the underbalance tolerance listed in the chart on (Sheet 5 of 5).
g. If modification of the rudder/elevator balance weight is necessary to correct an out-of-balance
condition, the balance weight can be lightened by drilling out part of the weight.
The weight
can be increased by fusing bar stock solder to the weight after removal from rudder/elevator.
BALANCING BEAM
Mark graduations in inches.
Four-foot length of extruded channel
Grind weight to slide along beam, grind
ends to obtain exactly one pound, and
mark center of weight.
marks center of-weight. Fabricate vertically adjustable
trailing edge support that will
slide along beam.
Attach knife edges and
mark at mid-point.
Detail A
Figure 18-3. Control Surface Balancing (Sheet 2 of 6)
Change 1
18-9