DOC AIRBUS | TSM A320FLEAK DETECTION - TASK SUPPORTING DATA
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. Typical Method of Trouble Shooting to Isolate the Faulty Element of the Overheat Detection System
A. Recommendations
(1) You must only use AC resistance meters with the characteristics that follow to make sure that the overheat detection system operates correctly:
- a maximum test voltage of 1VAC RMS
- a test signal of 1KHZ
- the possibility to measure the resistance value of a resistor which is in parallel with a capacitor.
(2) The sensing element of the overheat detection loop is serviceable when its measured insulation resistance is:
- for the APU loop more than 10 Kohms
- for the wing loops more than 10 Kohms
- for the engine/pylon loop more than 17 Kohms.
(3) When you do the trouble shooting of a loop that you think is unserviceable, use the usual techniques for electrical fault isolation, i.e. divide the system to find the location of the fault. After the end of the trouble shooting procedure, you must do a continuity check to make sure that the system operates correctly.
(4) Do not use DC meters because these can cause damage the sensing elements.
(5) There are no temperature or time restrictions when you use an AC resistance meter.
B. Typical Method (for example : sensing element 16HF)
Illustration of the leak detection - Electrical schematic(1) Make sure that the APU and the engines are not in operation.
(2) Put warning notices to prevent personnel not to start the APU or the engines.
(3) Open, safety and tag circuit breaker 2HA1 on this panel 122VU.
(4) Disconnect connector AA from the BMC1.
(5) Use an AC resistance meter (1VAC RMS maximum 1KHZ, test signal) to do a check of the resistance between pin 7B and ground.
(6) If the reading is below 10 Kohms, isolate half the loop to divide the system. To do this disconnect the connector between the sensing elements 16HF and 15HF. Do again a check of the resistance between pin 7B and ground. If the resistance is above 10 Kohms, this is an indication that the faulty element is located between the sensing elements 16HF and 19HF.
(7) Connect again the sensing element 15HF to the sensing element 16HF and then disconnect the sensing element 17HF from the sensing element 18HF. The meter shows that the resistance between pin 7B and ground is below 10 Kohms. The faulty element is this between sensing elements 16HF and 17HF.
(8) Disconnect the sensing element 16HF from the sensing element 17HF and do a check of the resistance. The value is below 10 Kohms: the sensing element 16HF is thus the faulty element and you must replace it.
2. Typical Method of Trouble Shooting to Isolate the Faulty Element of the Overheat Detection System
A. Recommendations
(1) You must only use AC resistance meters with the characteristics that follow to make sure that the overheat detection system operates correctly:
- a maximum test voltage of 1VAC RMS
- a test signal of 1KHZ
- the possibility to measure the resistance value of a resistor which is in parallel with a capacitor.
(2) The sensing element of the overheat detection loop is serviceable when its measured insulation resistance is:
- for the APU loop more than 10 Kohms
- for the wing loops more than 10 Kohms
- for the engine/pylon loop more than 17 Kohms.
(3) When you do the trouble shooting of a loop that you think is unserviceable, use the usual techniques for electrical fault isolation, i.e. divide the system to find the location of the fault. After the end of the trouble shooting procedure, you must do a continuity check to make sure that the system operates correctly.
(4) Do not use DC meters because these can cause damage the sensing elements.
(5) There are no temperature or time restrictions when you use an AC resistance meter.
B. Typical Method (for example : sensing element 16HF)
(1) Make sure that the APU and the engines are not in operation.
(2) Put warning notices to prevent personnel not to start the APU or the engines.
(3) Open, safety and tag circuit breaker 2HA1 on this panel 122VU.
(4) Disconnect connector AA from the BMC1.
(5) Use an AC resistance meter (1VAC RMS maximum 1KHZ, test signal) to do a check of the resistance between pin 7B and ground.
(6) If the reading is below 10 Kohms, isolate half the loop to divide the system. To do this disconnect the connector between the sensing elements 16HF and 15HF. Do again a check of the resistance between pin 7B and ground. If the resistance is above 10 Kohms, this is an indication that the faulty element is located between the sensing elements 16HF and 19HF.
(7) Connect again the sensing element 15HF to the sensing element 16HF and then disconnect the sensing element 17HF from the sensing element 18HF. The meter shows that the resistance between pin 7B and ground is below 10 Kohms. The faulty element is this between sensing elements 16HF and 17HF.
(8) Disconnect the sensing element 16HF from the sensing element 17HF and do a check of the resistance. The value is below 10 Kohms: the sensing element 16HF is thus the faulty element and you must replace it.