Cessna 150M - Balancing Beam

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
0
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 balancing 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 under balance 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.
Fabricate vertically adjustable
trailing edge support that will
slide along beam.
Detail A
Figure 18-3. Control Surface Balancing (Sheet 2 of 5)
18-9