Electrical Short Circuit/Arcing of Aged Aircraft Wiring

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$Atago Co., Ltd. Salinity Refractometer, Model S-10 Instruction Manual$

Figure 18. Preliminary Test A: Bundle after wet arc track testing for 5 minutes.Figure 19.Preliminary Test B: Oscillogram of current during intense flashing event.Electrical Arcing of Aged Aircraft Wire.Lectromechanical Design CompanyReport No. N191-RPT4AU99 August 12, 199920
Test 1 & 2Wet Arc TrackingBundle: Seven wires (6 over 1) of BMS 42A/8/1-20 specification, 15 inches in length.Electrolyte: 1% saline solution @ 200 mg/minute (test 1) , 100 mg/minute (test 2)Circuit Resistance: 1 OhmGenerator: 3 phase, 400Hz, 120 line to neutral (208 line to line), 10 kVA.Length of test: 20 minutes (Test 1), 25 minutes (Test 2)Observation Test 1 Test 2Visible scintillation 00:23 00:15Flash 16:01 8:44Strong Arcing No NoCircuit Breakers Tripped No NoDamage Length 1/2" 5/8"Number of Wires Failing WetDielectric Test2 of 5[C] & [B2]2 of 5[C] & [A2]The results of Test 1 and Test 2 were similar to each other though Test 2 did becomemore active a little sooner than did Test 1. Visible scintillations began within the first minute ofthe tests. In a couple of minutes, a char path began to develop between the two pre-damagedcracks in the insulation and scintillations were observed along this path. This is shown in Figure20.As the tests went on flashing events began to take place. At first the flashing events wereat least several seconds apart, sometimes they were up to a minute apart. Soon there were periodswhere the flash events repeated continuously, sometime several flashes per second. This wasfollowed by periods of dormancy where no electrical activity was observed. The intensity of theflash events varied both in the light and sound produced sometimes lasting several frames ofvideo. After a series of flashes a chemical combustion flame (candle-like flame) was observedburning the insulation for a few seconds (Figure 21). The samples were each tested between 20and 25 minutes and no circuit breakers tripped.Looking at the oscillograms taken during the more active times of the test, we see thatseveral of the flashing events lasted for 5 to 10 cycles. An example of this is shown in Figure 22which shows the current in one of the three phases during Test 1. The sequence begins with 8cycle consecutive cycles having high current for at least one of the ½ cycles and some times bothof the ½ cycles. This is followed by a period intermittent cycles of high current lasting for 50milliseconds followed by another 5 cycles that had continuous arcing currents. Not shown inFigure 22, but recorded on the oscilloscope, is that there were no high current cycles for the next4 seconds (corresponding to more than a 1000 cycles).Electrical Arcing of Aged Aircraft Wire.Lectromechanical Design CompanyReport No. N191-RPT4AU99 August 12, 199921
Page 3 and 4: Electrical Arcing of Aged Aircraft
Page 5 and 6: were placed between wires in small
Page 7 and 8: BackgroundArc tracking of aircraft
Page 9 and 10: EXPERIMENTAL PROCEDURESWet Arc Trac
Page 11 and 12: Figure 5. Circuit used in the metal
Page 13 and 14: Figure 8. Apparatus used for metal
Page 15 and 16: DESCRIPTION OF ELECTRICAL ACTIVITYT
Page 17 and 18: The voltage and current waveforms w
Page 19 and 20: Figure 15. Example of a strong arci
Page 21 and 22: RESULTSTable 1 lists the Test run g
Page 23 and 24: Table 3. Summary of Metal Shavings
Page 25: APPENDIX A: Description of Individu
Page 29 and 30: Figure 22. Test 1: Oscillogram show
Page 31 and 32: Test 3Wet Arc TrackingBundle: Seven
Page 33 and 34: Figure 26. Test 3: Sample bundle af
Page 35 and 36: Figure 27. Test 4: Strong arcing on
Page 37 and 38: Test 6 & 7Wet Arc TrackingBundle: S
Page 39 and 40: Figure 32. Test 6: Sample bundle af
Page 41 and 42: Test 9:Bundle: Seven wires (6 over
Page 49 and 50: Figure 37. Test 14: Electrical powe
Page 51 and 52: Metal Shavings AbrasionTest 16 A &
Page 53 and 54: Test 17 & 192 Bundles: four wires e
Page 55 and 56: Figure 42. Test 17: Damage to wire
Page 57 and 58: Figure 44. Test 20: Damage done in
Page 59 and 60: Table 7. Description of alternate a

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