Narrative:

An a-check was scheduled on a B737-900 aircraft. I was assigned the task cards associated with the #1 engine. Included in my assigned work was task card; engine qad torque check. This task was supposed to be performed on the #2 engine. I performed the task on the #1 engine. I assumed that; as all the other engine task cards related to the #1 engine; that this one was also for the # 1 engine. After I had gone home for the day; the dayshift lead noticed an error in the block on the task card for recording the position and engine serial number. I had entered the position of the engine on which I performed the task and the serial number for the engine that the task was supposed to be performed on. My supervisor assumed that I had merely made a typographical error for the engine position as the serial number that I recorded was the correct one for the engine on which the task was supposed to be performed. He asked me on which engine I performed the task; and I told him the #1 engine. This is how I found out that I had performed the task on the wrong engine. Many task cards are required to be accomplished to complete an a-check. Engine task cards are usually for one engine only. This task card was included in my assigned work but was not part of the a-check; but a stand alone task. I assumed that it was part of the check and accomplished the task on the engine for which all my other task cards were associated. Once we determined that the task was performed on the wrong engine; we contacted maintenance control to notify them of the problem. When an a-check is scheduled; if at all possible; work should not be assigned for the engine not associated with the a-check.

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Original NASA ASRS Text

Title: A Mechanic describes how assumptions led him to perform a QAD (Quick Attach/Detach) Ring task card check on #1 engine instead of #2 engine on a B737-900 during an A-Check.

Narrative: An A-Check was scheduled on a B737-900 aircraft. I was assigned the task cards associated with the #1 engine. Included in my assigned work was task card; Engine QAD Torque Check. This task was supposed to be performed on the #2 engine. I performed the task on the #1 engine. I assumed that; as all the other engine task cards related to the #1 engine; that this one was also for the # 1 engine. After I had gone home for the day; the dayshift Lead noticed an error in the block on the task card for recording the position and engine serial number. I had entered the position of the engine on which I performed the task and the serial number for the engine that the task was supposed to be performed on. My Supervisor assumed that I had merely made a typographical error for the engine position as the serial number that I recorded was the correct one for the engine on which the task was supposed to be performed. He asked me on which engine I performed the task; and I told him the #1 engine. This is how I found out that I had performed the task on the wrong engine. Many task cards are required to be accomplished to complete an A-Check. Engine task cards are usually for one engine only. This task card was included in my assigned work but was not part of the A-Check; but a stand alone task. I assumed that it was part of the check and accomplished the task on the engine for which all my other task cards were associated. Once we determined that the task was performed on the wrong engine; we contacted Maintenance Control to notify them of the problem. When an A-Check is scheduled; if at all possible; work should not be assigned for the engine not associated with the A-Check.

Data retrieved from NASA's ASRS site as of April 2012 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.