Maintenance Page 60
Air Tractor, Inc.
March 14, 2018
AT-502A/502B/504
in a cell indicates a bad cell. Replace the battery if it fails to meet this requirement. If the battery passes this
test, recharge it before returning it to service.
Oil Cooler Blower
The wiring schematic for the oil cooler blower is shown in Drawing 60084 with continuation on Drawing
60581. The Oil Cooler Blower is powered through the relay, p/n 51457. The relay is turned on
independently by the beta switch and the propeller-governor switch.
Engine Instruments
The NP Indicator, NG Indicator and the ITT Indicator are independent of the airplane’s electrical
system. They are powered by their respective tach-generators or thermocouple.
The Fuel Filter Pressure Light, Low Fuel Warn Light, Oil Temperature Indicator, Air Filter Pressure
Light, Chip Light, and Hour Meter are all powered by the airplane’s electrical system.
Engine Overspeed Solenoid
The wiring schematic for the Engine Overspeed Solenoid is shown in Drawing 60084.
Voltmeter
The wiring schematic for the Voltmeter is shown in Drawing 60084. The Voltmeter shows the voltage
on the airplane’s electrical bus. Voltmeter readings may be used to determine the condition of the battery
and Starter/Generator.
When the Master Switch is “ON”, with the Starter/Generator not charging, with no load on the system,
the fully-charged battery voltage should be between 23 and 24 volts. When the Starter/Generator is
charging, the voltage on the airplane bus should be approximately 28 volts.
Boost Pump
The wiring schematic for the boost pump is shown in Drawing 60129.
Fuel Gauging
The wiring schematic for the fuel gauging system is shown in Drawing 60198. The fuel quantity is
shown on the panel-mounted fuel gauge. Each of the wing fuel cells is gauged separately. The fuel quantity
in each of the fuel tanks is displayed on the panel fuel gauges.
The panel-mounted fuel gauge is a micro-ammeter with a full-scale range of 100 micro-amps. A circuit
board is attached to the binding posts of the instrument. Circuitry on this board provides a 4.3 -volt power
supply for the fuel-gauging system. This board also has a trimmer-potentiometer. This trimmer is used to
calibrate the full-scale readings on the micro-ammeter.
The sender is grounded through its mounting bolts.
Содержание AT-502A
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