Narrative:

During preflight flight deck set-up; discovered passenger oxygen manual deployment switch guard had been safety wired with non-frangible heavy wire. Logbook entry accomplished; maintenance notified. When maintenance technician arrived at aircraft he confirmed nonstandard wire and then we attempted to manually break the installed wire with no success. Maintenance technician removed non-frangible wire and installed proper wire. I suggest: 1) determine the history and if this was a contract maintenance issue that could have been applied improperly to other aircraft in our fleet. 2) due to the serious safety ramifications of improper wire being installed; initiate an immediate fleet wide inspection to correct any problems and improper installations. During that inspection; review proper safety wire for CSD/idg switch guards; and the alternate flaps master switch guard. 3) I have observed improper sized safety wire that has been installed randomly on aircraft I have been assigned since oct/2000. In all cases; the wire was too large and not frangible which could have contributed to an inability to accomplish abnormal or emergency procedures. A review of maintenance procedure for both 'in house' and contract vendors should be considered to preclude in-flight emergencys.

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Original NASA ASRS Text

Title: B737 CREW FOUND PAX OXYGEN MANUAL DEPLOYMENT SWITCH GUARDS SAFETY WIRED WITH NON-FRANGIBLE SAFETY WIRE ON PREFLT.

Narrative: DURING PREFLT FLT DECK SET-UP; DISCOVERED PAX OXYGEN MANUAL DEPLOYMENT SWITCH GUARD HAD BEEN SAFETY WIRED WITH NON-FRANGIBLE HVY WIRE. LOGBOOK ENTRY ACCOMPLISHED; MAINT NOTIFIED. WHEN MAINT TECHNICIAN ARRIVED AT ACFT HE CONFIRMED NONSTANDARD WIRE AND THEN WE ATTEMPTED TO MANUALLY BREAK THE INSTALLED WIRE WITH NO SUCCESS. MAINT TECHNICIAN REMOVED NON-FRANGIBLE WIRE AND INSTALLED PROPER WIRE. I SUGGEST: 1) DETERMINE THE HISTORY AND IF THIS WAS A CONTRACT MAINT ISSUE THAT COULD HAVE BEEN APPLIED IMPROPERLY TO OTHER ACFT IN OUR FLEET. 2) DUE TO THE SERIOUS SAFETY RAMIFICATIONS OF IMPROPER WIRE BEING INSTALLED; INITIATE AN IMMEDIATE FLEET WIDE INSPECTION TO CORRECT ANY PROBS AND IMPROPER INSTALLATIONS. DURING THAT INSPECTION; REVIEW PROPER SAFETY WIRE FOR CSD/IDG SWITCH GUARDS; AND THE ALTERNATE FLAPS MASTER SWITCH GUARD. 3) I HAVE OBSERVED IMPROPER SIZED SAFETY WIRE THAT HAS BEEN INSTALLED RANDOMLY ON ACFT I HAVE BEEN ASSIGNED SINCE OCT/2000. IN ALL CASES; THE WIRE WAS TOO LARGE AND NOT FRANGIBLE WHICH COULD HAVE CONTRIBUTED TO AN INABILITY TO ACCOMPLISH ABNORMAL OR EMER PROCS. A REVIEW OF MAINT PROC FOR BOTH 'IN HOUSE' AND CONTRACT VENDORS SHOULD BE CONSIDERED TO PRECLUDE INFLT EMERS.

Data retrieved from NASA's ASRS site as of January 2009 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.