Cessna 1969-1976 172 Series Service Manual page 136

9-3. TROUBLE SHOOTING (Cont).
TROUBLE
PROBABLE CAUSE
Cable tension too low.
Broken pulley.
Cable not in place on pulleys.
Worn t r i m tab actuator.
LOST MOTION BETWEEN
CONTROL WHEEL AND
TRIM TAB.
REMEDY
Check and adjust tension as
specified in figure 9- 1.
Open access plates and check
visually. Replace defective
pulley.
Open a c c e s s plates and check
visually. Install cables
correctly.
Remove and replace worn actuator.
TRIM INDICATOR FAILS TO
INDICATE CORRECT TRIM
POSITION.
INCORRECT TRIM TAB
I
TRAVEL.
Check actuator for security.
Tighten
a s
necessary.
I
Actuator attachment loose.
Indicator incorrectly engaged
on wheel track.
Check visually and reset
indicator
as necessary.
Adjust stop blocks on cables.
I
Refer to figure 9-2.
Stop blocks loose or incorrectly
adjusted.
9-4. TRIM TAB. (Refer to figure 8-2.)
9-5. REMOVAL AND INSTALLATION.
a. Disconnect push-pull channel (3) from horn
b. Drill out rivets attaching hinge to elevator.
assembly (4).
NOTE
After tab has been removed and if hinge pin
is to be removed, it is necessary to spread
the crimped ends of the hinge before driving
out pin. When
a pin has been installed,
crimp ends of hinge to prevent pin from work-
ing out.
c. Reverse preceding steps for installation.
9-6. TRIM TAB ACTUATOR.
9-7. REMOVAL AND INSTALLATION. (Refer to
figure 9- 1. )
Position
a support stand under tail tie-down
ring to prevent tailcone from dropping while
working inside.
a. Remove baggage compartment aft wall for ac-
cess.
b. Remove safety wire and relieve cable tension
at
turnbuckle (8).
c. Disconnect push-pull tube from actuator (3).
d. Remove a c c e s s plate from underside of right
e. Remove chain guard (2) and disengage chain (4)
f . Remove screws attaching actuator clamps to
hand stabilizer beneath actuator.
from actuator sprocket.
bracket and carefully work actuator out through ac-
c e s s opening.
g. Reverse the preceding steps for reinstallation.
Rig t r i m system in accordance with paragraph 9- 14,
safety turnbuckle (8) and reinstall all items removed
for access.
9-7A. DISASSEMBLY. (Refer to figure 9-3.)
a. Remove actuator in accordance with paragraph
9-7.
b. Disassemble actuator assembly (1)
as
illustrated
in Detail A
as
follows:
1. Remove chain guard (3) i f not previously r e -
moved in step "e" of paragraph 9-7.
2. Using suitable punch and hammer, remove
groov-pins (8) securing sprocket (5) to screw (9) and
4
remove sprocket from screw.
3. Unscrew threaded rod end (15) and remove
rod end from actuator.
4. Remove groov-pins (10) securing bearings
(6 and 14)
at
the housing ends.
5. Lightly tap screw (9) toward the sprocket
end of housing, remove bearing (6) and collar (7).
6. Lightly tap screw (9) in the opposite direc-
tion from sprocket end, remove bearing (14),
O-ring (13) and collar (7).
7. It is not necessary to remove retaining
rings (11).
9-2 Change 3