Narrative:

On landing in ZZZ; a passenger seen the access panel exit the B737-300 aircraft. One panel on top of pylon wasn't installed and was hanging by the cable over the outboard side of pylon and was visible from ground. I had just finished eating my lunch and my 2nd shift supervisor asked me if an employee number on a job card was mine. I said it was and he informed me by showing a picture of the top of the pylon with the panel not installed.previously; the acft was still in the hangar. The engine cowlings were still open because it had to be ran and leak checked; and one non-routine write-up on the outboard fan cowl hinge bushing was still in work. I was going to void my stamp (sign-off); in the 'accomplished by' block and short stamp the individual panels; but the oncoming inspector said he would see to it that the panel was installed.I should of either stayed later to finish installing the last panel; or voided out my 'accepted by' stamp. I took the inspector's word that he would see to it that the panel gets installed. I'm confident that someone attempted to install the panel because it stayed on throughout the flight and came off on landing. Aircraft had a cdl 54-20-01 placarded; and the next station downline installed the panel.I should not have stamped the 'accepted by' block. When performing an engine change several mechanics are accomplishing different tasks and one has to stamp for others work. The type fasteners in these panels have always been an issue the way they lock down. When there is a lot of paint present; it sometimes can be hard to tell if the latching portion is turned in the proper direction to be locked.

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Original NASA ASRS Text

Title: A Mechanic reports a passenger had seen an access panel on top of an engine pylon exit the B737-300 aircraft. Mechanic had earlier signed for the panel installation when the aircraft was still in the hangar; after being reassured by the oncoming Inspector; the panel would be installed after the engine cowls were closed up.

Narrative: On landing in ZZZ; a passenger seen the access panel exit the B737-300 aircraft. One panel on top of pylon wasn't installed and was hanging by the cable over the outboard side of pylon and was visible from ground. I had just finished eating my lunch and my 2nd Shift Supervisor asked me if an employee number on a Job Card was mine. I said it was and he informed me by showing a picture of the top of the pylon with the panel not installed.Previously; the acft was still in the hangar. The engine cowlings were still open because it had to be ran and leak checked; and one Non-Routine Write-up on the outboard Fan cowl hinge bushing was still in work. I was going to void my Stamp (sign-off); in the 'Accomplished by' block and Short Stamp the individual panels; but the oncoming Inspector said he would see to it that the panel was installed.I should of either stayed later to finish installing the last panel; or voided out my 'Accepted by' Stamp. I took the Inspector's word that he would see to it that the panel gets installed. I'm confident that someone attempted to install the panel because it stayed on throughout the flight and came off on landing. Aircraft had a CDL 54-20-01 placarded; and the next station downline installed the panel.I should not have stamped the 'Accepted by' block. When performing an engine change several Mechanics are accomplishing different Tasks and one has to Stamp for others work. The type fasteners in these panels have always been an issue the way they lock down. When there is a lot of paint present; it sometimes can be hard to tell if the latching portion is turned in the proper direction to be locked.

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.