Cessna T303 Installation, Service & Parts Manual page 273

Avionic in stallations Service/Parts Manual
deflection at mid span of cacle,
c. If cable tension is too high, remove safety
wire (26) from turnbuckle (29) and then loosen turn-
buckle until the desired .25 inch cable deflection is
obtained. If cable tension is too low, tighten to ob-
tain the desired .25 inch cable deflection.
d. After cable adjustment is completed, rein-
stall safety wire (26) on turnbuckle (28).
Step 8. Remove the bar securing the control
wheels which was attached in step 1.
Step 9. In order to eliminate the gyro roll and
pitch signals generated by a non-erected gyro, the
400B autopilot has a GYRO switch located on the rear
of the control head; set the GYRO switch to the OUT
position. Since the 400B IFCS does not have a gyro
out switch, it will be necessary to hook up an outside
vacuum source or operate one of the aircraft engines
to erect the gyro.
NOTES
If an outside vacuum source is used, it should
be calibrated in inches of mercury and the
desired suction range required to erect the
gyro is 4. 6 to 5. 4 inches of mercury.
If one of the aircraft's engines is operated to
erect the gyro, the engine should be run at
1000 RPM to provide the desired amount of
vacuum and maintain proper bus voltage.
Step 10. Turn aircraft master switch, L & R
avionics power and autopilot (AP) switch ON. Using
the autopilot's PULL-TURN knob (pull out on 400B
autopilot), check operation of aileron travel in both
directions. (After several seconds, ailerons will
move slowly in desired direction. Aileron travel
need not be full in either direction. Typical control
wheel travel will be 1/3 to 2/3 of full traveL)
NOTES
Due to ground loads applied to the ailerons,
aileron travel from stop to stop cannot be
obtained in most instances while conducting
ground tests. In view of this fact, the ser-
vice technician should use care in observ-
ing the preceeding procedures in step 10 and
not assume the aileron actuator is not com-
pletely operational. Flight tests in accord-
ance with the appropriate 400B Service/Parts
Manual should be conducted after rigging
procedures checkout to fully determine if
the system is completely operational.
Check that autopilot may be overpowered
using the control wheels at any time; how-
ever, this practice should be kept to a min-
imum since extended manual operation will
overheat the actuator, causing a thermo-
static switch to remove power from the act-
uator.
Step 11. Turn OFF the autopilot (AP) switch.
avionics power switches and aircraft master switch.
Step 12. Replace access plates and carpeting
that was removed in step 2.
Aileron Friction Band Check.
The desired aileron
friction band without an autopilot installed is 4
pounds or less. The maximum allowable friction
band is 6 pounds with an autopilot installed. The
friction band shall be checked everytime the auto-
pilot rigging is checked. The friction band shall be
measured and calculated in accordance with Steps 1
and 2. Corrective action to reduce the aileron sys-
tem friction band shall be accomplished in accord-
ance with Step 3.
Step 1. Friction Band Measurements - All fric-
tion measurements shall be made with the load scale
so situated that the force exerted to move the aileron
is applied tangentially to and in the place of the con-
trol wheel assembly. The load scale shall be at-
tached to the control wheel assembly at the longest
possible moment arm (inside the grip). The friction
band requirements apply over the complete travel of
the ailerons. For purposes of production inspection,
one reading, taken as the control wheel assembly
passes the aileron neutral position, will suffice
a. With the control wheel rotated to approxi-
mately 30° in the CCW direction, attach the load
scale and exert a force as above to rotate the wheel
in a CW direction. Take the scale reading as the
control wheel passes the aileron neutral position.
Identify this force as F
1
.
b. With the control wheel rotated to approxi-
mately 30° in the CW direction, attach the load scale
and exert a force as above to rotate the wheel in a
CCW direction. Take the scale reading as the con-
trol wheel passes the aileron neutral position. Iden-
tify this force as F
2
.
Step 2.
Friction Band Calculation - The aileron
friction band is calculated by adding measured forces
F
1
and F2.
Friction Band - F
1
+ F2
Step 3. Corrective Action - When the friction
band exceeds the limitations of 6 pounds, the follow-
ing steps shall be taken in the order shown to reduce
the system friction to an acceptable level:
a. Check aileron direct, aileron return, inter-
connect, and rudder cables for clearance and elimi-
nate all interference as indicated.
b. Reduce aileron cable tension as required
(minimum tension 30 pounds) with ailerons in neu-
tral position.
Figure 7-1.
Rigging Procedures for Cessna 400B and 400B IFCS (Types AF-550A & IF-550A) (Sheet 5 of 14)
7-6