4-56. CHECKING CONTROL SURFACE BALANCE.
The movable control surfaces have been statically balanced at the time of installation at the factory and
normally should not require rebalancing. Where possible, the control surfaces were set with the balance weight
on the heavy side of the limits, to permit limited repair or paint touch-up without adjusting the balance weight. It
should be noted however, that spare control surfaces are delivered unpainted and the static balance will not
necessarily fall within the limits provided, this is more pronounced on the stabilators and rudders. The completed
control surface, including paint, should be within the limits given in Table lV-I. If the surface is not to be painted,
the balance weight will probably require adjustment. All replacement control surfaces. or surfaces that have been
repainted or repaired, should be rebalanced according to the procedures given in Paragraphs 4-58 thru 4-60. The
static balance of the surfaces must be as specified in Table IV-I.
Before balancing any control surface, it must be complete including tip, trim/ servo tabs and tab actuating
arms or push rods with bearings as applicable, and all optional equipment which is mounted on or in the control
surface when it is flown, including paint, position lights and wiring, static wicks, scuff boots, etc.
If optional equipment is added or removed after balancing, the control surface must be rebalanced. During
balancing, trim/servo tabs must be maintained in their neutral positions.
4-57. BALANCING EQUIPMENT. (Refer to Figure 4-20.)
Balancing must be done using a suitable tool capable of measuring unbalance in inch-pounds from the
centerline of the control surface hinge pin. A suggested configuration is shown in Figure 4-11.
To use this tool:
a. Insure that the control surface is in its final right configuration, static wicks, trim tabs, trim tab push pull
rod and control surface tip (as applicable) should be installed. The surface should be painted and trim/servo tabs
should be in the neutral position.
b. Place hinge bolts through control surfaces and place control surface on a holding fixture.
c. Avoiding rivets, place the balancing tool on the control surface with the tool's hinge centerline directly
over the hinge line of the control surface.
d. Adjust the movable trailing edge support to fit the width of the control surface. Tighten the set screw on
the trailing edge support.
e. Adjust the trailing edge support vertically until the beam is parallel with the control surface chord line.
f. Remove the tool from the control surface and balance the tool itself by adding or removing nuts or washers
from the beam balancing bolt. When balancing the tool, the movable weight must be at the bar's hinge centerline
.g. After balancing the tool, reattach it to the control surface. Keep the beam positioned 90o from the control
surface hinge line.
h. Determine balance of control surface by sliding movable weight along the balance beam.
i. Read the scale when the bubble in the level has been centered. Since the movable weight weighs three
pounds, every inch it is moved from the center of the beam equals three inch-pounds of force.
—NOTE—
Because paint is a considerable balance factor, it is recommended that existing
paint be removed prior to repainting a control surface.
PIPER AIRCRAFT
PA-28-161 CADET
AIRPLANE MAINTENANCE MANUAL
STRUCTURES
1F8
Issued: FEBRUARY. 28, 1989
