Narrative:

The following is my account of the maintenance that was performed on aircraft XXX. Also included is the incident resulting from error in this maintenance, as well as, what factors attributed to this. In conclusion, I have stated what steps I believe could prevent this from occurring again. Aircraft XXX was in for overnight maintenance with inspections involving the engine sync and autothrottle system. During troubleshooting of these system the night shift technician discovered that the left throttle was sticking when moved to the full forward position. He troubleshot this problem by disconnecting the throttle at the bell crank in the aft cargo pit, the throttle cables where they attach to the engine xshaft, and the fuel control unit. He discovered that with the throttle disconnected from the engine xshaft, the binding of the throttle ceased. The aircraft was then repositioned to the hangar on one engine with the left throttle cable disconnected from the engine. A turnover was given to me at this point. After reading the turnover, I personally talked with the night shift technician about what was left disconnected. In the logbook were write-ups for the throttle cable bolt and nut being removed at the xshaft, as well as the cotter pin for a bolt attaching the throttle control tube at the fuel control unit. This is the point I began troubleshooting. The throttle binding discrepancy was caused by the position of the bracket that attaches the throttle and fuel shutoff cables to the engine. This bracket is slotted. Simply by repositioning this bracket, the binding discrepancy was solved. However, repositioning the bracket threw off the idle rig at the xshaft. The throttle cable was rigged for idle along with the engine sync followed by installing both engine part power stops to check throttle knob split. Once this maintenance was complete, the items involved in the rigging were safetied and inspected by a required inspection item inspector. In addition, the cargo pit was opened for this inspector since items involving the throttle were touched by the previous shift. This was done for safety purposes regardless of the fact that there were no write-ups. At this point, maintenance control called and informed us that the aircraft was needed immediately for revenue flight. We had not completed any of the paperwork at this point. The paperwork was completed and the write-up on the cotter pin, which was removed from the bolt at the fuel control unit, was read and misinterped by me to have been the cotter pin removed at the xshaft. Therefore, no cotter pin was installed by me nor inspected for by me at the fuel control unit. The incident resulting from this misinterp was the loss of throttle control in-flight. This loss of control led to an in-flight shutdown, emergency landing, and the destruction of an engine due to overtemping and thermal shock. Misinterping the exact write-up that was written was the predominant cause first officer this incident. There were also a number of other contributing factors. An obvious factor was the immediate need for the aircraft, which was a change in this aircraft's status. The fact that there were too many loose ends and undocumented maintenance at the time of turnover created problems as well. In a situation where further troubleshooting is still required at turnover time, all areas that have been looked at or touched need to be completely secured and signed off. Maintenance personnel taking turnovers in a troubleshooting situation are focused on solving the problem. This practice relieves the burden of overlooking what someone else has or has not done. It would also be helpful at turnover time to have a lead present and involved in the decision of what should be turned over and/or what should be wrapped up by the leaving shift. A simple turnover with less strings attached is always better and less confusing. It would take a minimal amount of time for a technician to clean up the project to a point that would simplify the turnover. These are standard practices, which if followed, would minimize misinterps in the future. During troubleshooting, it is very easy for a technician to become so focused on searching for the problem that he manages to open too many areas of the aircraft. He moves on if he does not find a problem in a certain area. This is a common occurrence and if documented there really isn't anything wrong with it until turnover time. If the technician is planning to give a turnover, he must cease the troubleshooting in advance to close areas and put things back together completely. A good standard practice is to put things back together completely. If you do not have the time to finish, or the assembly is not specifically outlined in the manual or work card, do not begin the assembly. This simple practice will not only prevent misinterps, it will prevent the questions that usually arise and consequently lead to the disassembly back to the starting point by someone other than the original mechanic.

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Original NASA ASRS Text

Title: AN MD80 MECH FORGETS TO SECURE THE FUEL CTL UNIT WITH THE REQUIRED COTTER PIN WHICH CREATES AN INFLT ENG SHUTDOWN AFTER THE ENG SUSTAINED AN OVERHEAT CONDITION, AFTER TKOF AND CRUISE, TOTALING THE ENG. ZZZ, US.

Narrative: THE FOLLOWING IS MY ACCOUNT OF THE MAINT THAT WAS PERFORMED ON ACFT XXX. ALSO INCLUDED IS THE INCIDENT RESULTING FROM ERROR IN THIS MAINT, AS WELL AS, WHAT FACTORS ATTRIBUTED TO THIS. IN CONCLUSION, I HAVE STATED WHAT STEPS I BELIEVE COULD PREVENT THIS FROM OCCURRING AGAIN. ACFT XXX WAS IN FOR OVERNIGHT MAINT WITH INSPECTIONS INVOLVING THE ENG SYNC AND AUTOTHROTTLE SYS. DURING TROUBLESHOOTING OF THESE SYS THE NIGHT SHIFT TECHNICIAN DISCOVERED THAT THE L THROTTLE WAS STICKING WHEN MOVED TO THE FULL FORWARD POS. HE TROUBLESHOT THIS PROB BY DISCONNECTING THE THROTTLE AT THE BELL CRANK IN THE AFT CARGO PIT, THE THROTTLE CABLES WHERE THEY ATTACH TO THE ENG XSHAFT, AND THE FUEL CTL UNIT. HE DISCOVERED THAT WITH THE THROTTLE DISCONNECTED FROM THE ENG XSHAFT, THE BINDING OF THE THROTTLE CEASED. THE ACFT WAS THEN REPOSITIONED TO THE HANGAR ON ONE ENG WITH THE L THROTTLE CABLE DISCONNECTED FROM THE ENG. A TURNOVER WAS GIVEN TO ME AT THIS POINT. AFTER READING THE TURNOVER, I PERSONALLY TALKED WITH THE NIGHT SHIFT TECHNICIAN ABOUT WHAT WAS LEFT DISCONNECTED. IN THE LOGBOOK WERE WRITE-UPS FOR THE THROTTLE CABLE BOLT AND NUT BEING REMOVED AT THE XSHAFT, AS WELL AS THE COTTER PIN FOR A BOLT ATTACHING THE THROTTLE CTL TUBE AT THE FUEL CTL UNIT. THIS IS THE POINT I BEGAN TROUBLESHOOTING. THE THROTTLE BINDING DISCREPANCY WAS CAUSED BY THE POS OF THE BRACKET THAT ATTACHES THE THROTTLE AND FUEL SHUTOFF CABLES TO THE ENG. THIS BRACKET IS SLOTTED. SIMPLY BY REPOSITIONING THIS BRACKET, THE BINDING DISCREPANCY WAS SOLVED. HOWEVER, REPOSITIONING THE BRACKET THREW OFF THE IDLE RIG AT THE XSHAFT. THE THROTTLE CABLE WAS RIGGED FOR IDLE ALONG WITH THE ENG SYNC FOLLOWED BY INSTALLING BOTH ENG PART PWR STOPS TO CHK THROTTLE KNOB SPLIT. ONCE THIS MAINT WAS COMPLETE, THE ITEMS INVOLVED IN THE RIGGING WERE SAFETIED AND INSPECTED BY A REQUIRED INSPECTION ITEM INSPECTOR. IN ADDITION, THE CARGO PIT WAS OPENED FOR THIS INSPECTOR SINCE ITEMS INVOLVING THE THROTTLE WERE TOUCHED BY THE PREVIOUS SHIFT. THIS WAS DONE FOR SAFETY PURPOSES REGARDLESS OF THE FACT THAT THERE WERE NO WRITE-UPS. AT THIS POINT, MAINT CTL CALLED AND INFORMED US THAT THE ACFT WAS NEEDED IMMEDIATELY FOR REVENUE FLT. WE HAD NOT COMPLETED ANY OF THE PAPERWORK AT THIS POINT. THE PAPERWORK WAS COMPLETED AND THE WRITE-UP ON THE COTTER PIN, WHICH WAS REMOVED FROM THE BOLT AT THE FUEL CTL UNIT, WAS READ AND MISINTERPED BY ME TO HAVE BEEN THE COTTER PIN REMOVED AT THE XSHAFT. THEREFORE, NO COTTER PIN WAS INSTALLED BY ME NOR INSPECTED FOR BY ME AT THE FUEL CTL UNIT. THE INCIDENT RESULTING FROM THIS MISINTERP WAS THE LOSS OF THROTTLE CTL INFLT. THIS LOSS OF CTL LED TO AN INFLT SHUTDOWN, EMER LNDG, AND THE DESTRUCTION OF AN ENG DUE TO OVERTEMPING AND THERMAL SHOCK. MISINTERPING THE EXACT WRITE-UP THAT WAS WRITTEN WAS THE PREDOMINANT CAUSE FO THIS INCIDENT. THERE WERE ALSO A NUMBER OF OTHER CONTRIBUTING FACTORS. AN OBVIOUS FACTOR WAS THE IMMEDIATE NEED FOR THE ACFT, WHICH WAS A CHANGE IN THIS ACFT'S STATUS. THE FACT THAT THERE WERE TOO MANY LOOSE ENDS AND UNDOCUMENTED MAINT AT THE TIME OF TURNOVER CREATED PROBS AS WELL. IN A SIT WHERE FURTHER TROUBLESHOOTING IS STILL REQUIRED AT TURNOVER TIME, ALL AREAS THAT HAVE BEEN LOOKED AT OR TOUCHED NEED TO BE COMPLETELY SECURED AND SIGNED OFF. MAINT PERSONNEL TAKING TURNOVERS IN A TROUBLESHOOTING SIT ARE FOCUSED ON SOLVING THE PROB. THIS PRACTICE RELIEVES THE BURDEN OF OVERLOOKING WHAT SOMEONE ELSE HAS OR HAS NOT DONE. IT WOULD ALSO BE HELPFUL AT TURNOVER TIME TO HAVE A LEAD PRESENT AND INVOLVED IN THE DECISION OF WHAT SHOULD BE TURNED OVER AND/OR WHAT SHOULD BE WRAPPED UP BY THE LEAVING SHIFT. A SIMPLE TURNOVER WITH LESS STRINGS ATTACHED IS ALWAYS BETTER AND LESS CONFUSING. IT WOULD TAKE A MINIMAL AMOUNT OF TIME FOR A TECHNICIAN TO CLEAN UP THE PROJECT TO A POINT THAT WOULD SIMPLIFY THE TURNOVER. THESE ARE STANDARD PRACTICES, WHICH IF FOLLOWED, WOULD MINIMIZE MISINTERPS IN THE FUTURE. DURING TROUBLESHOOTING, IT IS VERY EASY FOR A TECHNICIAN TO BECOME SO FOCUSED ON SEARCHING FOR THE PROB THAT HE MANAGES TO OPEN TOO MANY AREAS OF THE ACFT. HE MOVES ON IF HE DOES NOT FIND A PROB IN A CERTAIN AREA. THIS IS A COMMON OCCURRENCE AND IF DOCUMENTED THERE REALLY ISN'T ANYTHING WRONG WITH IT UNTIL TURNOVER TIME. IF THE TECHNICIAN IS PLANNING TO GIVE A TURNOVER, HE MUST CEASE THE TROUBLESHOOTING IN ADVANCE TO CLOSE AREAS AND PUT THINGS BACK TOGETHER COMPLETELY. A GOOD STANDARD PRACTICE IS TO PUT THINGS BACK TOGETHER COMPLETELY. IF YOU DO NOT HAVE THE TIME TO FINISH, OR THE ASSEMBLY IS NOT SPECIFICALLY OUTLINED IN THE MANUAL OR WORK CARD, DO NOT BEGIN THE ASSEMBLY. THIS SIMPLE PRACTICE WILL NOT ONLY PREVENT MISINTERPS, IT WILL PREVENT THE QUESTIONS THAT USUALLY ARISE AND CONSEQUENTLY LEAD TO THE DISASSEMBLY BACK TO THE STARTING POINT BY SOMEONE OTHER THAN THE ORIGINAL MECH.

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.