Narrative:

In oct 2001, mr X and I were assigned aircraft X. Mr X was assigned as a mechanic and I was assigned as the inspector for control cable tension inspection. In november of 2004, aircraft X was in for maintenance and it was discovered that the rudder body cable turn barrels near the aft pressure bulkhead were not safetied with turn barrel locks. There are four turn barrels, three of the four had no locks, and the fourth was safetied with safety wire. I cannot recollect any specifics of events for that day three years ago but I am certain that the maintenance was done correctly per the maintenance manual as indicated by the completed non-routines associated with this special inspection and I have never used safety wire or bought off turn barrels safetied with safety wire in my employment with air carrier. In the past three years since mr X and I completed this task there has been an abundance of maintenance performed in the area of interest. 2001, C3 check. 2002, C4 check. 2002, C1 check. 2002, C2 check. 2002, forward slider cracked on left/H stabilizer. 2003, flight control cable pulley hardware. 2003, C3 check. 2003, elevator cable pulley and bolt installation. 2003, dual feel diff press light at 41000 ft, cleaned elevator pitot moisture drains. 2003, horizontal stabilizer motor change. 2003, C4 check. 2003, readjusted captain and first officer's elevator control cables. 2003, elevator cable pulley hardware inspection. 2003, C1 check. 2004, stabilizer trim actuator lube. 2004, stabilizer trim actuator lube. 2004, stabilizer trim actuator lube. 2004, left forward stabilizer slider cracked. 2004, brg check. 2004, HC1 check. There are many more scenarios that could have happened to these cable locks. One that I believe should be looked into further is that aircraft X was in for a C4 in 2003 where the area aft of the pressure bulkhead was heavily inspected and the elevator cables in the same area were unlocked, re-tensioned and safetied. The mechanic performing the elevator cable adjustment may have started removing the locks on the rudder cables instead of the elevator cables. The mechanic could have removed three of the four locks before realizing the wrong cables were being unlocked. In order to complete the assigned job, the mechanic may have moved on to the correct cable locks, leaving the rudder cables not safetied intending to return later. The inspector may have already finished the C4 inspection of the aft compartment before the rudder cable locks were mistakenly removed. When the elevator cable job was complete, the inspector looked at the elevator cables. After the mechanic and inspector were completed with the elevator cable adjustment, the rudder cable locks were forgotten about. Why else would only one of the four turn barrels be safetied? If you examine the photos that were taken of the unlocked cables, you will see that the turn barrels were lined up with the slot in the threaded portion of the cable end. The position they would be if a lock was just removed. The rudder cables were found unlocked nov/04 while adjusting the horizontal stabilizer cables, which are adjusted from forward east&east. Why were they noticed then and not during any other time where maintenance was being done in that area in three years? Using safety wire to lock turn barrels is not used in air carrier X where turn barrel locks are readily available. I have asked many inspectors and mechanics in air carrier X who say they have not used safety wire when turn barrel locks are available. I have never used or inspected any cable turn barrel using safety wire to lock the turn barrels. Callback conversation with reporter revealed the following information: the reporter worked on this airplane three years ago and inspected the original tension check when the airplane was delivered and the cables were found stretching. The procedure for the cable check is to check the actual cable tension with a calibrated instrument and if found out of limits to adjust the turnbuckle. The cables were found out of limits and adjustment was required. The procedure is to remove the turnbuckle locks and adjust as required and thenreplace the turnbuckle locks. In the area aft of the pressure dome, cable turnbuckle locks are used as there is plenty of space and not safety wire that would be used in a limited access area. These turnbuckle locks were removed at some subsequent maintenance activity with no non routine write up made by person or persons doing the turnbuckle lock removal. The reporter stated that no aircraft would leave their maintenance facility without cable turnbuckle locks installed. Supplemental information from acn 638010: I was made aware of an issue found during the 'D' check of aircraft X in ZZZ in nov/2004. The last documented maintenance done on the system was done in oct/2001 by me. The system in question is a rudder cable tension rig. I was told that 3 of the 4 turnbuckles were unsafetied. The fourth buckle was safetied with wire. I consider this highly suspect, not only due to the time that has passed, but because the only buckle safetied was with wire. No one safties with wire first of all, but rather they use wire after clips cannot be installed. I believe some one else removed the clips, possibly believing it was another system and forgot to resafety them. Also, in 3 yrs, I would believe someone would have noticed unsafetied buckles. There has been an untold number of people in the area, including inspectors in phase 'C' checks. I believe that at the time the work was accomplished, it was at 100%. If anything, this shows a huge hole in our maintenance prog. Possible inspection of this system may be needed.

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Original NASA ASRS Text

Title: A B737-700 UNDERGOING A D MAINT CHECK WAS FOUND TO BE MISSING THREE OUT OF FOUR TURN BARREL LOCKS ON THE RUDDER BODY CABLE TURN BARRELS.

Narrative: IN OCT 2001, MR X AND I WERE ASSIGNED ACFT X. MR X WAS ASSIGNED AS A MECHANIC AND I WAS ASSIGNED AS THE INSPECTOR FOR CONTROL CABLE TENSION INSPECTION. IN NOVEMBER OF 2004, ACFT X WAS IN FOR MAINT AND IT WAS DISCOVERED THAT THE RUDDER BODY CABLE TURN BARRELS NEAR THE AFT PRESSURE BULKHEAD WERE NOT SAFETIED WITH TURN BARREL LOCKS. THERE ARE FOUR TURN BARRELS, THREE OF THE FOUR HAD NO LOCKS, AND THE FOURTH WAS SAFETIED WITH SAFETY WIRE. I CANNOT RECOLLECT ANY SPECIFICS OF EVENTS FOR THAT DAY THREE YEARS AGO BUT I AM CERTAIN THAT THE MAINT WAS DONE CORRECTLY PER THE MAINT MANUAL AS INDICATED BY THE COMPLETED NON-ROUTINES ASSOCIATED WITH THIS SPECIAL INSPECTION AND I HAVE NEVER USED SAFETY WIRE OR BOUGHT OFF TURN BARRELS SAFETIED WITH SAFETY WIRE IN MY EMPLOYMENT WITH AIR CARRIER. IN THE PAST THREE YEARS SINCE MR X AND I COMPLETED THIS TASK THERE HAS BEEN AN ABUNDANCE OF MAINT PERFORMED IN THE AREA OF INTEREST. 2001, C3 CHK. 2002, C4 CHK. 2002, C1 CHK. 2002, C2 CHK. 2002, FORWARD SLIDER CRACKED ON L/H STABILIZER. 2003, FLT CTL CABLE PULLEY HARDWARE. 2003, C3 CHK. 2003, ELEVATOR CABLE PULLEY AND BOLT INSTALLATION. 2003, DUAL FEEL DIFF PRESS LIGHT AT 41000 FT, CLEANED ELEVATOR PITOT MOISTURE DRAINS. 2003, HORIZONTAL STABILIZER MOTOR CHANGE. 2003, C4 CHK. 2003, READJUSTED CAPT AND FO'S ELEVATOR CTL CABLES. 2003, ELEVATOR CABLE PULLEY HARDWARE INSPECTION. 2003, C1 CHK. 2004, STAB TRIM ACTUATOR LUBE. 2004, STAB TRIM ACTUATOR LUBE. 2004, STAB TRIM ACTUATOR LUBE. 2004, LEFT FORWARD STAB SLIDER CRACKED. 2004, BRG CHK. 2004, HC1 CHK. THERE ARE MANY MORE SCENARIOS THAT COULD HAVE HAPPENED TO THESE CABLE LOCKS. ONE THAT I BELIEVE SHOULD BE LOOKED INTO FURTHER IS THAT ACFT X WAS IN FOR A C4 IN 2003 WHERE THE AREA AFT OF THE PRESSURE BULKHEAD WAS HEAVILY INSPECTED AND THE ELEVATOR CABLES IN THE SAME AREA WERE UNLOCKED, RE-TENSIONED AND SAFETIED. THE MECHANIC PERFORMING THE ELEVATOR CABLE ADJUSTMENT MAY HAVE STARTED REMOVING THE LOCKS ON THE RUDDER CABLES INSTEAD OF THE ELEVATOR CABLES. THE MECHANIC COULD HAVE REMOVED THREE OF THE FOUR LOCKS BEFORE REALIZING THE WRONG CABLES WERE BEING UNLOCKED. IN ORDER TO COMPLETE THE ASSIGNED JOB, THE MECHANIC MAY HAVE MOVED ON TO THE CORRECT CABLE LOCKS, LEAVING THE RUDDER CABLES NOT SAFETIED INTENDING TO RETURN LATER. THE INSPECTOR MAY HAVE ALREADY FINISHED THE C4 INSPECTION OF THE AFT COMPARTMENT BEFORE THE RUDDER CABLE LOCKS WERE MISTAKENLY REMOVED. WHEN THE ELEVATOR CABLE JOB WAS COMPLETE, THE INSPECTOR LOOKED AT THE ELEVATOR CABLES. AFTER THE MECHANIC AND INSPECTOR WERE COMPLETED WITH THE ELEVATOR CABLE ADJUSTMENT, THE RUDDER CABLE LOCKS WERE FORGOTTEN ABOUT. WHY ELSE WOULD ONLY ONE OF THE FOUR TURN BARRELS BE SAFETIED? IF YOU EXAMINE THE PHOTOS THAT WERE TAKEN OF THE UNLOCKED CABLES, YOU WILL SEE THAT THE TURN BARRELS WERE LINED UP WITH THE SLOT IN THE THREADED PORTION OF THE CABLE END. THE POSITION THEY WOULD BE IF A LOCK WAS JUST REMOVED. THE RUDDER CABLES WERE FOUND UNLOCKED NOV/04 WHILE ADJUSTING THE HORIZONTAL STAB CABLES, WHICH ARE ADJUSTED FROM FORWARD E&E. WHY WERE THEY NOTICED THEN AND NOT DURING ANY OTHER TIME WHERE MAINT WAS BEING DONE IN THAT AREA IN THREE YEARS? USING SAFETY WIRE TO LOCK TURN BARRELS IS NOT USED IN ACR X WHERE TURN BARREL LOCKS ARE READILY AVAILABLE. I HAVE ASKED MANY INSPECTORS AND MECHANICS IN ACR X WHO SAY THEY HAVE NOT USED SAFETY WIRE WHEN TURN BARREL LOCKS ARE AVAILABLE. I HAVE NEVER USED OR INSPECTED ANY CABLE TURN BARREL USING SAFETY WIRE TO LOCK THE TURN BARRELS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR WORKED ON THIS AIRPLANE THREE YEARS AGO AND INSPECTED THE ORIGINAL TENSION CHECK WHEN THE AIRPLANE WAS DELIVERED AND THE CABLES WERE FOUND STRETCHING. THE PROC FOR THE CABLE CHECK IS TO CHECK THE ACTUAL CABLE TENSION WITH A CALIBRATED INSTRUMENT AND IF FOUND OUT OF LIMITS TO ADJUST THE TURNBUCKLE. THE CABLES WERE FOUND OUT OF LIMITS AND ADJUSTMENT WAS REQUIRED. THE PROC IS TO REMOVE THE TURNBUCKLE LOCKS AND ADJUST AS REQUIRED AND THENREPLACE THE TURNBUCKLE LOCKS. IN THE AREA AFT OF THE PRESSURE DOME, CABLE TURNBUCKLE LOCKS ARE USED AS THERE IS PLENTY OF SPACE AND NOT SAFETY WIRE THAT WOULD BE USED IN A LIMITED ACCESS AREA. THESE TURNBUCKLE LOCKS WERE REMOVED AT SOME SUBSEQUENT MAINT ACTIVITY WITH NO NON ROUTINE WRITE UP MADE BY PERSON OR PERSONS DOING THE TURNBUCKLE LOCK REMOVAL. THE RPTR STATED THAT NO ACFT WOULD LEAVE THEIR MAINT FACILITY WITHOUT CABLE TURNBUCKLE LOCKS INSTALLED. SUPPLEMENTAL INFO FROM ACN 638010: I WAS MADE AWARE OF AN ISSUE FOUND DURING THE 'D' CHK OF ACFT X IN ZZZ IN NOV/2004. THE LAST DOCUMENTED MAINT DONE ON THE SYSTEM WAS DONE IN OCT/2001 BY ME. THE SYSTEM IN QUESTION IS A RUDDER CABLE TENSION RIG. I WAS TOLD THAT 3 OF THE 4 TURNBUCKLES WERE UNSAFETIED. THE FOURTH BUCKLE WAS SAFETIED WITH WIRE. I CONSIDER THIS HIGHLY SUSPECT, NOT ONLY DUE TO THE TIME THAT HAS PASSED, BUT BECAUSE THE ONLY BUCKLE SAFETIED WAS WITH WIRE. NO ONE SAFTIES WITH WIRE FIRST OF ALL, BUT RATHER THEY USE WIRE AFTER CLIPS CANNOT BE INSTALLED. I BELIEVE SOME ONE ELSE REMOVED THE CLIPS, POSSIBLY BELIEVING IT WAS ANOTHER SYSTEM AND FORGOT TO RESAFETY THEM. ALSO, IN 3 YRS, I WOULD BELIEVE SOMEONE WOULD HAVE NOTICED UNSAFETIED BUCKLES. THERE HAS BEEN AN UNTOLD NUMBER OF PEOPLE IN THE AREA, INCLUDING INSPECTORS IN PHASE 'C' CHKS. I BELIEVE THAT AT THE TIME THE WORK WAS ACCOMPLISHED, IT WAS AT 100%. IF ANYTHING, THIS SHOWS A HUGE HOLE IN OUR MAINT PROG. POSSIBLE INSPECTION OF THIS SYSTEM MAY BE NEEDED.

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.