Air carrier mechanic working on APU feed line, accidentally reversed terminals. Lighting conditions ...

Attributes
ACN	332016
Time
Date	199603
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : zzz
State Reference	US
Altitude	agl bound lower : 0 agl bound upper : 0
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	ground : preflight
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	other personnel other
Qualification	other other : other
ASRS Report	332016
Events
Anomaly	aircraft equipment problem : less severe non adherence : published procedure other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

Aircraft was found to have APU generator feed line broken between the APU and the APU generator contactor. I removed several terminals, ensuring they were marked, on the contactor to prevent snagging of terminal wires while replacing the feed line. After splicing of the feed line was accomplished, I resecured the terminals to the contactor. The APU was started and the system checked, and the aircraft was dispatched. Over the next approximately 36 hours, external power was never applied to the aircraft. When it finally was, the aircraft was found to accept external power with the switch in the off position. After troubleshooting, maintenance personnel discovered that terminals 6NO and 6NC were crossed. The wires were uncrossed and the problem was resolved and the discrepancy was cleared. Working in the poor lighting of the electrics and avionics compartment and my flashlight dimming from continued use, I evidently misread the wire markings 6NO and 6NC and crossed them as I resecured the terminal wires. The identing marks imprinted on the contactor were not readily visible to me, being obscured by the body of the contactor.

Original NASA ASRS Text

Title: ACR MECH WORKING ON APU FEED LINE, ACCIDENTALLY REVERSED TERMINALS. LIGHTING CONDITIONS WERE POOR AND THE TERMINALS 6NO AND 6NC, WHICH WERE CROSSED, COULD BE EASILY MIXED, AND WERE. WHEN, AFTER 36 HRS OF FLYING, GND PWR WAS CONNECTED TO THE ACFT, EXTERNAL PWR WAS CONNECTED WITH THE SWITCH IN THE OFF POS.

Narrative: ACFT WAS FOUND TO HAVE APU GENERATOR FEED LINE BROKEN BTWN THE APU AND THE APU GENERATOR CONTACTOR. I REMOVED SEVERAL TERMINALS, ENSURING THEY WERE MARKED, ON THE CONTACTOR TO PREVENT SNAGGING OF TERMINAL WIRES WHILE REPLACING THE FEED LINE. AFTER SPLICING OF THE FEED LINE WAS ACCOMPLISHED, I RESECURED THE TERMINALS TO THE CONTACTOR. THE APU WAS STARTED AND THE SYS CHKED, AND THE ACFT WAS DISPATCHED. OVER THE NEXT APPROX 36 HRS, EXTERNAL PWR WAS NEVER APPLIED TO THE ACFT. WHEN IT FINALLY WAS, THE ACFT WAS FOUND TO ACCEPT EXTERNAL PWR WITH THE SWITCH IN THE OFF POS. AFTER TROUBLESHOOTING, MAINT PERSONNEL DISCOVERED THAT TERMINALS 6NO AND 6NC WERE CROSSED. THE WIRES WERE UNCROSSED AND THE PROB WAS RESOLVED AND THE DISCREPANCY WAS CLRED. WORKING IN THE POOR LIGHTING OF THE ELECTRICS AND AVIONICS COMPARTMENT AND MY FLASHLIGHT DIMMING FROM CONTINUED USE, I EVIDENTLY MISREAD THE WIRE MARKINGS 6NO AND 6NC AND CROSSED THEM AS I RESECURED THE TERMINAL WIRES. THE IDENTING MARKS IMPRINTED ON THE CONTACTOR WERE NOT READILY VISIBLE TO ME, BEING OBSCURED BY THE BODY OF THE CONTACTOR.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.