4. Prepare to Adjust APU Control Thermostat (Using Thermostat Calibration Kit)
A. Remove the EGT thermocouple probe (AMM 49-71-21/401).
B. Install the test thermocouple:
(1)
Install the test thermocouple from the thermocouple calibration kit.
(2)
Connect the test thermocouple cable to the calibration kit.
C. Do a check of the set-point for the thermostat temperature control and the control time for the rate of the load control valve:
(1)
Close the circuit breaker on M280 module-APU accessory unit on E3-3 electronic shelf.
(2)
Set the BATTERY SWITCH to the ON position.
(3)
With one person in the cockpit and one person monitoring the indicator on the calibration kit, operate the APU (AMM 49-11-0/201):
(a)
Let the APU become stable for 1 to 2 minutes with no load applied.
(b)
Record the EGT indication from the EGT indicator in the cockpit.
(4)
Set the L PACK and R PACK valve switches to the ON position.
(5)
Make sure the engines 1 and/or 2 BLEED switches on the P5 forward overhead panel are in the OFF position.
(6)
Set the ISOLATION VALVE switch to the AUTO position.
(7)
Set the APU BLEED AIR valve switch to the ON position.
(8)
Set the cabin temperature selector to the MANUAL COLD position until the air mix valves indicate COLD.
(9)
Incrementally put an electrical load of 60 amps on the APU electrical generator.
(10)
Let the EGT become stable for 1 to 2 minutes.
(11)
Monitor the temperature indicator in the calibration kit to see when the EGT becomes stable.
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(a) This temperature is the control temperature of the thermostat and must be between 620-650°C (1148-1202°F).
NOTE: This temperature must not be more than 650°C (1202°F).
(12)
Set the L PACK and R PACK valve switches to the OFF position.
(13)
Set the cabin temperature selector to the OFF position.
(14)
Set the APU BLEED AIR valve switch to the OFF position.
(15)
Set the ISOLATION VALVE switch to the CLOSE position.
(16)
Remove the electrical load of 60 amps from the electrical generator.
(17)
Let the APU become stable for 1 to 2 minutes with no load applied.
(18)
Set the APU master switch to the OFF position.
(19)
If EGT in step (11) was not met, adjust control thermostat per par. 6.
5. Adjust APU Control Thermostat (Using Airplane Instrumentation)
A. Using temperature (EGT) noted in step 3.B.(9), adjust thermostat as necessary.
(1)
Observing that each index mark on the adjustment head equals 2°C (36°F), rotate adjustment collar in a clockwise direction (viewed from fitting end) to increase temperature setting.
(2)
Rotate adjustment collar in a counterclockwise direction to decrease temperature setting.
NOTE: There are two self-locking helicoil inserts located in the adjustable collar to prevent the collar from rotating and changing calibration in service. To ensure integrity of this locking device, the torque on the adjustment collar should be observed during adjustment. If the running torque on the adjustment collar is less than 20 pound-inches, the thermostat must be removed from service for repair.
B. Do this procedure: Prepare to Test APU Control Thermostat (Using Airplane Instrumentation) per par. 3. If the thermostat is still out of limits repeat par. 5.
6. Adjust APU Control Thermostat (Using Thermostat Calibration Kit)
A. If the control temperature of the APU control thermostat is not in the limits, adjust the
thermostat:
(1)
If the control temperature is too low, turn the adjustment collar clockwise (viewed from the fitting end) to increase the temperature.
(2)
If the control temperature is too high, turn the adjustment collar counterclockwise to decrease the temperature.
NOTE: Each index mark on the adjustment is the same as 2°C (36°F).
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NOTE: There are two self-locking insert sleeves in the adjustable collar to prevent a collar movement during the operation. To make sure this device operates correctly, monitor the quantity of torque that is necessary to turn the adjustment collar. If the torque is less than 20 pound-inches, you must replace the thermostat.
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