Cessna 150M - Balancing Procedures; Control Surface Balancing

BALANCING PROCEDURES
1. Balance control surfaces in an .enclosed draft free area.
2. Control surface to be balanced must be in the final flight configuration, painted (if applicable) trim
tabs installed, and all foreign matter removed from inside control surface.
3. If control surface is to be painted remove all existing paint prior to repainting and rebalancing. Good
workmanship and standard repair practices should not result in excessive additional balance weight.
4. Place balancing mandrels (detail B) on a table or other suitable FLAT, LEVELED surface. Man-
drels must be placed at 90
0
to the hinge line of the control surface.
5. On control surfaces with the piano type hinges, insert inboard and outboard hinges into slotted ends
of the balancing mandrels, making sure that balancing mandrels are 90
0
to the hinge line. On
control surfaces with the bearing type hinge point, bolts or pins are inserted through the attaching
brackets, then placed on the knife edges of the mandrels as illustrated in (detail H).
6.
AILERONS.
18-8
a.
(1) Block up the trailing edge of the aileron until a spirit-level protractor placed on the front
face of the aileron spar at W. S. 138. 00 (± 6. 00), (detail E), indicates 57
0
10', (detail D).
(2) ALTERNATE METHOD:
Measure the vertical distance from the aileron hinge point to the leveled surface. Subtract
1. 80 inches, then block up trailing edge of the aileron to this measurement.
b. With the aileron blocked in position place the balancing beam (detail A) at W. S. 138. 00, (90 a to
the hinge
line), and adjust the trailing edge support on the balancing beam (detail D) until the
beam is level. If the aileron has not been disturbed during this operation, the beam is now
parallel to the aileron chord line at W. S. 138. 00 (detail D).
NOTE
The above procedure must be performed with care. Small angular discrepancies
will produce large balancing errors.
c. Remove balancing beam and balance the beam by itself at the knife edges by adding washers as
shown, (detail C).
d. Place the balancing beam on the aileron in its original position, then remove the blocks from
beneath the trailing edge.
e. Place the sliding weight (detail D) on the forward end of the balancing beam, moving 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 aileron hinge line (detail D).
f. If aileron is correctly balanced, the position of the sliding weight with respect to the aileron
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 aileron balance weight is necessary to correct an out-of-tolerance
condition, the balance weight can be lightened by drilling out part of the weight on the in-
board end. The weight can be increased by a reasonable amount by ordering additional
weight and gang channel listed in the applicable Parts Catalog, and installing next to the
existing weight the minimum amount necessary for correct balance. The minimum
amount that must be installed, however, must contain at least two attaching rivets. If this
minimum amount results in an over-balanced condition, the new weight and/or old weights
can be lightened.
Figure 18-3. Control Surface Balancing (Sheet 1 of 5)