D.
The single point sensors are found in the No. 2 and 3 main tanks and are located at the fuel level for 6000 U.S. gallons (22,700 liters).
NOTE: The 6K GAL. fuel level is set for an in-flight airplane at the
____
time of reserve tank fuel transfer.
(1) On the ground the fuel quantity that is necessary to cover the single point sensors with fuel will change with different fuel densities or airplane attitudes. These fuel quantities will make sure the SPS senors are always "dry" or "wet" at all nominal airplane ground attitudes and fuel densities:
MGMT M2 M3 SPS "DRY" inputs, maximum of 5500 gals (20,820 liters) MGMT M2 M3 SPS "WET" inputs, minimum of 6600 gals (24,980 liters)
E. To find out if the fuel level is above or below the single point sensors, go to the fuel system card file and look at the the MGMT M2 M3 SPS control card in slot A2.
(1)
If the two green LEDs are on, the fuel level is below the single point sensor.
(2)
If the two LEDs are off, the fuel level is above the single point sensor.
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MAINTENANCE MANUAL
ELECTROSTATIC GROUND JACK
FUEL SYSTEM CARD FILE
SEE A
A
A
FUEL SYSTEM CARD FILE A
CARD A2A-A Reserve Tank Transfer Single Point Sensor Control Card Figure 501
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F. The two sensors are identified as channel 1 (CH1) and channel 2 (CH2). CH1 agrees with the single-point sensor, probe F116 (SSM 28-44-01). CH2 agrees with the single-point sensor, probe F118 (SSM 28-44-01).
G. The single-point sensor control card includes several test functions to check the operation of CH1 and CH2. The test functions includes these components:
(1)
A CH1 and CH2 LED. The LED is "on" and the color is green when the fuel level is below the single point sensors in the No. 2 and 3 main tanks (the sensor is dry). The LED is "off" if the fuel level is above the single point sensors (the sensor is wet). The circuit is considered opened when the sensors are wet (LED is off) and grounded when the sensors are dry (LED is on).
(2)
A CH1 and CH2 BIT switch. The three position (center off) toggle switch on the SPS card allows for a check of the SPS control card logic.
(a)
If the fuel level is above the sensors (SPS wet - approximately 10-12 pF) and the CH1 or CH2 BIT is activated, a low fuel level is simulated. After approximately four seconds, the output changes state (becomes grounded) and the BIT LED comes on.
(b)
If the fuel level is below the sensors (SPS dry - approximately 3.5-9.0 pF) and the CH1 or CH2 BIT function is activated, the output changes state immediately and the BIT LED goes off.
(c)
If the SPS capacitance is out of range (below 3.5 Pf or above
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