Cessna 172 Maintenance Manual page 44

1. General
A. This section applies to the balancing of the ailerons, elevators, and rudder. Control surface balance
must be verified after repair or painting.
B. Proper balance of control surfaces is critical to prevent flutter during normal operating conditions.
2. Tools and Equipment
NAME
Control Surface
Balance Fixture Kit
Scale 0-10 Pounds
in 0.01 Pound
increments
3. Procedures for Balancing Control Surfaces
A. The flight control surface balancing fixture kit (part number 5180002-1) is shown in Figure 1.
(1) Balance of control surfaces must be accomplished in a draft free room or area.
(2) Place hinge bolts through control surface hinges and position on knife edge balancing mandrels,
refer to Figure 2 for positioning of balancing control surfaces.
(3) Make sure all control surfaces are in their approved flight configuration; painted (if applicable),
trim tabs installed, static wicks, and all tips installed.
(4) Place balancing mandrels on a table or other suitable flat surface.
(5) Adjust trailing edge support to fit control surface being balanced while center of balancing beam
is directly over hinge line. Remove balancing beam and balance the beam itself by adding
washers or nuts required at end opposite the trailing edge support.
(6) When positioning balancing beam on control surface, avoid rivets to provide a smooth surface
for the beam and keep the beam 90 degrees to the hinge line of control surface.
(7) Paint is a considerable weight factor.
is recommended that existing paint be removed before adding paint to a control surface.
Increase in balance weight will also be limited by the amount of space available and clearance
with adjacent parts. Good workmanship and standard repair practices should not result in
unreasonable balance weight.
(8) The approximate amount of weight needed may be determined by taping loose weight at the
balance weight area.
(9) Lighten balance weight by drilling off part of weight.
(10) Make balance weight heavier by fusing bar stock solder to weight after removal from control
surface. The ailerons should have balance weight increased by ordering additional weight and
gang channel, listed in applicable Parts Catalog, and installing next to existing inboard weight
the minimum length necessary for correct balance, except that a length which contains at least
two attaching screws must be used. If necessary, lighten new weight or existing weights for
correct balance.
4. Balancing Definitions
A. Overbalance (refer to Figure 3) is defined as the condition that exists when surface is leading edge
heavy and is defined by symbol (-). If the balance beam uses a sliding weight, the weight must be on
the trailing edge side of the hinge line (to balance the control surface), the control surface is considered
to be overbalanced.
CESSNA AIRCRAFT COMPANY
SINGLE ENGINE
STRUCTURAL REPAIR MANUAL
FLIGHT CONTROL SURFACE BALANCING
NUMBER
5180002–1
© Cessna Aircraft Company
MANUFACTURER
Cessna Aircraft Co. Cessna
Part Distribution
5800 E. Pawnee
P.O. Box 1521
Wichita, KS 67218
Commercially Available
In order to keep balance weight to a minimum, it
USE
Balance elevator and
aileron.
Balance rudder
51-60-00
Page 1
Jun 1/2005