Narrative:

We were to swap aircraft during the turnaround. On the inbound leg of the trip; I delegated the duties upon our arrival. The so would go to the new aircraft and conduct the preflight inspection; the first officer would go to operations and do the paperwork; and I would go to the hangar and exchange aircraft logbooks and join first officer at operations. The first officer asserted that he would prefer to go to the aircraft and assist the so by preflting the upper wing. This is not SOP. But; it was past my bedtime. I did not protest. The area where the aircraft was parked was very dark. The aircraft required heat. And; engine blankets may have obscured the fasteners of the accessory panels. (I say 'may have' because the first officer and the so cannot agree as to whether blankets were; or were not; in place.) shortly after departure; after gear up; I felt a disturbance in the seat of my pants. It was a short yawing motion. It was subtle. I asked the crew if they had felt it or seen anything on the panel. They had not. I passed it off as a disturbance caused by some bad air. Upon arrival at our ZZZ facility; maintenance personnel brought to my attention that the #1 engine; upper and lower; accessory compartment access panels were missing. About 40% of the fasteners remained in their respective sockets. According to the aircraft logbook; maintenance personnel may have been inside this compartment prior to our preflight. Why a mechanic would partially fasten a panel; is unknown. Why the 2 airmen I delegated to preflight the aircraft did not notice the partially unfastened panels; is unknown. Why the ground crew who removed the blankets and heaters from the engines; did not notice the partially unfastened panels; is unknown.

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Original NASA ASRS Text

Title: A DC6 CAPT REPORTS AN ENG ACCESSORY PANEL FELL OFF AFTER TKOF. THE FO AND SO FAILED TO SEE FASTENERS LOOSE DURING PREFLT.

Narrative: WE WERE TO SWAP ACFT DURING THE TURNAROUND. ON THE INBOUND LEG OF THE TRIP; I DELEGATED THE DUTIES UPON OUR ARR. THE SO WOULD GO TO THE NEW ACFT AND CONDUCT THE PREFLT INSPECTION; THE FO WOULD GO TO OPS AND DO THE PAPERWORK; AND I WOULD GO TO THE HANGAR AND EXCHANGE ACFT LOGBOOKS AND JOIN FO AT OPS. THE FO ASSERTED THAT HE WOULD PREFER TO GO TO THE ACFT AND ASSIST THE SO BY PREFLTING THE UPPER WING. THIS IS NOT SOP. BUT; IT WAS PAST MY BEDTIME. I DID NOT PROTEST. THE AREA WHERE THE ACFT WAS PARKED WAS VERY DARK. THE ACFT REQUIRED HEAT. AND; ENG BLANKETS MAY HAVE OBSCURED THE FASTENERS OF THE ACCESSORY PANELS. (I SAY 'MAY HAVE' BECAUSE THE FO AND THE SO CANNOT AGREE AS TO WHETHER BLANKETS WERE; OR WERE NOT; IN PLACE.) SHORTLY AFTER DEP; AFTER GEAR UP; I FELT A DISTURBANCE IN THE SEAT OF MY PANTS. IT WAS A SHORT YAWING MOTION. IT WAS SUBTLE. I ASKED THE CREW IF THEY HAD FELT IT OR SEEN ANYTHING ON THE PANEL. THEY HAD NOT. I PASSED IT OFF AS A DISTURBANCE CAUSED BY SOME BAD AIR. UPON ARR AT OUR ZZZ FACILITY; MAINT PERSONNEL BROUGHT TO MY ATTN THAT THE #1 ENG; UPPER AND LOWER; ACCESSORY COMPARTMENT ACCESS PANELS WERE MISSING. ABOUT 40% OF THE FASTENERS REMAINED IN THEIR RESPECTIVE SOCKETS. ACCORDING TO THE ACFT LOGBOOK; MAINT PERSONNEL MAY HAVE BEEN INSIDE THIS COMPARTMENT PRIOR TO OUR PREFLT. WHY A MECH WOULD PARTIALLY FASTEN A PANEL; IS UNKNOWN. WHY THE 2 AIRMEN I DELEGATED TO PREFLT THE ACFT DID NOT NOTICE THE PARTIALLY UNFASTENED PANELS; IS UNKNOWN. WHY THE GND CREW WHO REMOVED THE BLANKETS AND HEATERS FROM THE ENGS; DID NOT NOTICE THE PARTIALLY UNFASTENED PANELS; IS UNKNOWN.

Data retrieved from NASA's ASRS site as of May 2009 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.