Narrative:

In sum: the reporter flew 2 different ATR42-300 aircraft on 2 different days which had malfunctioning bus off lights. When dc bus #1 was not energized the bus off light for #2 bus would illuminate and vice versa. The aircraft were in turn noticed to maintenance and corrected with some painful interaction between the various personnel. Callback conversation with reporter revealed the following information: the reporter found that 2 of the ATR42-300's that he was operating had been improperly wired during manufacture so that a failure of bus #1 could cause the bus #2 off light to illuminate and the reverse indication for a bus #2 failure. The mechanics in each case found the wire bundles still tied with factory supplied ties and connectors. When the wires were traced and then changed the indications were then corrected. The reporter was the safety chairman for his union at the time, and he had some resistance to his efforts to check the other aircraft in the fleet and he is not sure that this was ever done. ATR was notified through pilot's group and they have reported no other incidents. The reporter is suspicious that this investigation was not very precise since it was done very quickly. The reporter also stated that the serial numbers between the 2 miswired aircraft differed by 103 numbers, but the registration numbers by only one leading the reporter to wonder if 103 aircraft had the same miswiring of the bus protection control unit. The reporter also stated that the management attempted to punish him when he wrote these discrepancies in the maintenance log.

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Original NASA ASRS Text

Title: ACR FLC FINDS THAT AT LEAST 2 OF THE ATR42-300'S IN THEIR FLEET HAD THE BUS OFF LIGHTS CROSS-WIRED BY THE FACTORY. ATR WAS CONTACTED THROUGH PLT'S GROUP AND THEY RPT NO PROBS WITH THE FLEET. THESE IMPROPER INDICATIONS COULD LEAD TO SERIOUS CONSEQUENCES IF THERE WERE A GENERATOR FAILURE IN IMC IF THE REMAINING GENERATOR WERE SHUT OFF.

Narrative: IN SUM: THE RPTR FLEW 2 DIFFERENT ATR42-300 ACFT ON 2 DIFFERENT DAYS WHICH HAD MALFUNCTIONING BUS OFF LIGHTS. WHEN DC BUS #1 WAS NOT ENERGIZED THE BUS OFF LIGHT FOR #2 BUS WOULD ILLUMINATE AND VICE VERSA. THE ACFT WERE IN TURN NOTICED TO MAINT AND CORRECTED WITH SOME PAINFUL INTERACTION BTWN THE VARIOUS PERSONNEL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR FOUND THAT 2 OF THE ATR42-300'S THAT HE WAS OPERATING HAD BEEN IMPROPERLY WIRED DURING MANUFACTURE SO THAT A FAILURE OF BUS #1 COULD CAUSE THE BUS #2 OFF LIGHT TO ILLUMINATE AND THE REVERSE INDICATION FOR A BUS #2 FAILURE. THE MECHS IN EACH CASE FOUND THE WIRE BUNDLES STILL TIED WITH FACTORY SUPPLIED TIES AND CONNECTORS. WHEN THE WIRES WERE TRACED AND THEN CHANGED THE INDICATIONS WERE THEN CORRECTED. THE RPTR WAS THE SAFETY CHAIRMAN FOR HIS UNION AT THE TIME, AND HE HAD SOME RESISTANCE TO HIS EFFORTS TO CHK THE OTHER ACFT IN THE FLEET AND HE IS NOT SURE THAT THIS WAS EVER DONE. ATR WAS NOTIFIED THROUGH PLT'S GROUP AND THEY HAVE RPTED NO OTHER INCIDENTS. THE RPTR IS SUSPICIOUS THAT THIS INVESTIGATION WAS NOT VERY PRECISE SINCE IT WAS DONE VERY QUICKLY. THE RPTR ALSO STATED THAT THE SERIAL NUMBERS BTWN THE 2 MISWIRED ACFT DIFFERED BY 103 NUMBERS, BUT THE REGISTRATION NUMBERS BY ONLY ONE LEADING THE RPTR TO WONDER IF 103 ACFT HAD THE SAME MISWIRING OF THE BUS PROTECTION CTL UNIT. THE RPTR ALSO STATED THAT THE MGMNT ATTEMPTED TO PUNISH HIM WHEN HE WROTE THESE DISCREPANCIES IN THE MAINT LOG.

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.