AIR TRACTOR AT-502A, Maintenance Section

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Air Tractor, Inc. Maintenance Page 19
AT-502A/502B/504 March 14, 2018
See drawing 60198 for flap system wiring schematic. The actuator jack screw is fitted with a stop to
mechanically limit the ball nut travel in case of a problem with the down microswitch or relay. If you replace
the actuator, the new one will come with a new stop nut. To install the stop nut, first install p/n 70037-1
"teenut", that was installed on the old actuator, on the new ball screw. Install the tee nut with Loctite RC-609
after cleaning the threads. Install the AN565D6H4 set screw. Now that the Tee nut is installed, install the
left hand thread stop nut with Loctite RC-609. Torque the stop nut. Weld the stop nut to the jack screw as
described in SL #165. Install the shield with the AN500A5-3 screw and lock washer. Be sure not to leave
out the lock washer. Safety wire the screws.
Flap Actuator Removal Instructions:
1. Disconnect all wires at Wristlock connections in wire harness and identify wires for re-assembly.
2.
Remove the 4 AN4 bolts that attach the aluminum arms on the flap “Tee” to the torque tube.
CAUTION: Have someone hold up on the flap trailing edge before the last bolt is removed.
3. Remove the nut and washer from the AN4 bolt attaching the actuator assembly to the fuselage frame.
4. Remove the AN4 bolt, paying close attention to the spacer bushing inside the bronze bushing, and
lower the flaps to rest on boom hangers.
5. Check rubber coupling on motor shaft for excessive back-lash.
With the complete actuator on the work bench, if it is desired to change the actuator itself, perform the
following:
1. Remove the two screws that hold the dust shield to the lower end of the assembly.
2. Use open end wrench to remove down over-ride stop from end of jack-screw. CAUTION: This stop is
left-hand threads.
3.
Loosen the set screw in the top of the “Tee” assembly with a small Allen wrench.
4. With water-pump pliers or vise-
grips, break loose the collar from the “Tee” assembly.
5.
Unscrew striker by hand out of “Tee” assembly.
Flap Actuator Installation Instructions:
1. Re-install actuator in aircraft in reverse order as removal.
2. Raise flaps to full up position with flap switch in cockpit. Check position of flaps relative to wing (See
Flap and Aileron Rigging section of this manual).
3. With flaps properly positioned with respect to the lower side of the wing there should be a gap 1/16" to
1/8" between the striker and the end of the up travel (See Note 5, drawing 70031). If the gap is not
within the range above, use the flap switch in the cockpit to provide the proper gap. Then it will be
necessary to set the flap position with respect to the lower wing surface by adjusting the flap pushrods
.
4. Then loosen the two screws holding the UP micro-switch and adjust the micro-switch until a click is
heard. Tighten the two screws and once more use the flap switch in the cockpit to lower and then raise
the flaps to the full up position. Again check the gap between the striker and the end of the up travel for
1/16" to 1/8" travel. Check position of flaps with respect to the wing lower surface. If all is in order,
proceed to set the down micro-switch.
5. Extend the flaps to 26
o
and adjust the lower micro-switch until a click is heard. Re-cycle the flaps and
check down travel again.