Date: 201206
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Pax Seat
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Time Pressure; Workload; Communication Breakdown; Distraction; Fatigue; Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Maintenance
When detected: Other Paperwork Audit
Result: General Maintenance Action
Contributing factors: Manuals; Procedure; Aircraft; Chart Or Publication; Company Policy; Human Factors; Incorrect / Not Installed / Unavailable Part
Primary problem: Human Factors

Narrative: I was assigned that night with another Mechanic (Y) to perform Line Routine Overnight (RON) Maintenance on Aircraft X and Y. I took Aircraft X while (Mechanic Y) worked Aircraft Y. I had changed two nose tires on another aircraft before working my Maintenance Visit Check on Aircraft X. I changed a taxi turn-off light and the # 2 Main tire before completing all assigned work cards and the Maintenance Visit Check (M/V) on Aircraft X. I then assisted Mechanic Y with the M/V Check on Aircraft Y by changing the # 3 Main Landing Gear (MLG) tire and both nose tires. Once done with the tire changes; I inquired what was left to do. Mechanic Y had completed all other work on Aircraft Y and had just finished replacing Passenger Seat Row XDEF. It was getting very late in the night (Morning) and we still had to complete all the paperwork. I assisted him in placing the old seat row on a cart for transport and filled out the Serviceable Parts Tag for him. I tilted the seat assembly in such a manner that I could read the seat Data Plate underneath. I saw several part numbers along with the Serial Number (S/N). Being fatigued and under time constraints; I transcribed the Serviceable Manufacturer's Part Number and Item Number for logbook onto the Removal section of the Parts Tag. I then documented the seat Serial Number (S/N) onto the tag. We rushed inside to complete both aircraft work packages before departure time. I completed Aircraft X's paperwork and also signed for the three tire changes on Aircraft Y. Mechanic Y pulled the Parts Compatibility list for the Main Ship Battery; O2 Bottle and the seat row. All showed to have correct 'Effectivity' and he signed-off his work package. We handed the paperwork to our Supervisor for review. We were done! Since; I was told that after his review our Supervisor handed the packet to the paperwork clerk and the plane was released with only a few minutes before departure time. Shortly after the plane took off the clerk noticed that the seat S/N # for the Manufacturer's P/N did not match. This mismatch caused the investigation to reveal that we had installed an 'Effective' part; but not at the location Row YDEF. It was in fact for row ZDEF. It is my opinion that this situation was caused by several broken links; failures and outside factors. An MEL was written for the wrong seat row; which led to the wrong seat to be ordered. This seat was installed and I filled out the Serviceable Parts Tag incorrectly. The seat row location was overlooked on the Parts Compatibility list. Several people failed to catch this oversight primarily due to workload; fatigue and time constraints. I am glad the Clerk discovered the mistake. However; I am very sad that Aircraft Y left and flew before it could be corrected. I could have broken the chain of events had I noticed the Manufacturer's Part number mismatch.[Recommend] reducing fatigue; adjusting headcount; moving personnel according to workload requirements; and changing the Parts Compatibility computer screen to alert the Aircraft Maintenance Technician (AMT) of critical positioning of the part [on the aircraft].




Synopsis: A Line Mechanic performing multiple tasks on two aircraft with another Mechanic was informed they had installed a replacement Passenger Seat Row that was effective for the B737 aircraft; but not at the row they had installed it.