AIR TRACTOR AT-502A, Maintenance Section

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Air Tractor, Inc. Maintenance Page 61
AT-502A/502B/504 March 14, 2018
Wing Flaps
The wiring schematic for the wing flaps is shown in Drawing 60198. Power to drive the flaps up and
down is provided by the cockpit flap switch. The wiring from the flap switch is routed through the micro-
switches that serve as limit switches for the full "ON" and full "DOWN" positions.
Stall-Warning Horn
The wiring schematic for the stall-warning horn is shown in Drawing 60198. The horn is connected in
series with the lift-detector switch that is located near the leading edge of at mid-span of the right-hand wing.
The lift-detector switch is controlled by a tab that projects forward into the prevailing airstream. When at rest,
the weight of the tab holds it down, opening the switch. When the airflow around the lift detector shifts to a
forward direction, the tab is lifted, closing the switch and causing the horn to sound.
Windshield Washer
The wiring schematic for the windshield washer is shown in Drawing 60118. When the switch is closed,
the pump’s motor starts and the solenoid valve is opened. The flow of windshield-washing fluid will continue
until the switch is released. The purpose of the solenoid is to provide a sharp cut-off of fluid when the switch
is released. This prevents the dribbling of fluid onto the windshield.
Windshield Wiper
The wiring schematic for the windshield wiper is shown in Drawing 60250. The wiper switch has three
positions, “HIGH”, “LOW”, and “PARK”. When the switch is in the “PARK” position, the wiper blades are
parked and the power to the wiper motor is off.
Cockpit Lighting
The wiring schematic for the cockpit lights is shown in Drawing 60059 p2. The intensity level of the
cockpit lights, except for the dome and map lights, is controlled by the solid-state dimming circuit.
When the panel light switch is turned “ON”, power is available to the dimming circuit. The panel-light
intensity is controlled by the panel-light rheostat on the instrument panel.
Flap Light
The wiring schematic for the flap light is shown in Drawing 60059. The flap light is located in a housing
on the upper side of the left-hand wing just forward of the wing flap, near the center of the span of the flap.
The light illuminates marks on the leading edge of the flap, providing an indication of the amount of deflection
of the flap. The flap light is controlled by the instrument-light switch, but it is not dimmed by the panel-light
dimming circuitry.