Narrative:

Immediately after gear up from takeoff from 10L, the right side cabin crew door came open causing the first officer and myself to bring the aircraft around for an uneventful landing to 10L. The majority of the preflight, including the walk around had been completed by myself. Nothing unusual had been noted on the mdt. The cabin door that came open was the right side fuselage forward of wing and propeller. It's a door that, in our operation, is never used because the crew enters from a hydraulic door on left side. IFR clearance had been received for our 45 min flight to sea and after freight was loaded and cargo door closed, we started and taxied out with no unusual indications. The door light check had been completed immediately before starting and all indications were normal. Our first takeoff attempt was aborted on my decision because at approximately 80 KTS, our door open light began flickering. Upon exiting the runway, the light extinguished and stayed extinguished. On the taxi back, I stopped the aircraft and checked the entry door we use since that's the only door I didn't personally close. The entry door was opened and relatched and a look at the door in question showed handle in trail, which was the indication to me that the door was latched. Another takeoff clearance was received after another successful door light test. This takeoff roll was all normal through rotation and immediately after gear up and locked the door blew open. The clam shell door, hinged from the top continued to 'fly' as we brought the aircraft around for landing on 10L. We returned to our ramp and shut down to determine the cause. My observation showed no damage to the door and we could find no malfunction with the locking mechanism. The microswitch was found to be dirty because of the lack of activity on the door. After personally closing and locking the door, the flight was continued without incident. In my further investigation, the next morning, I found out a fueler had gained entry through the door in question because he didn't know how to operate the hydraulic door he left a fuel slip in the cockpit and, upon exiting, he incorrectly closed the door. With the mechanical latches in question, it's possible for the door to appear closed and latched. The latching mechanism wasn't fully latched but just partially latched. At approximately 140 KTS after takeoff, the force was enough to pull the hooks off the latches and let the door blow open. A simple relatching of the door on my part would have illuminated this incident. Because the 'service door' is never used, crew members tend to take for granted the proper latching of the door. A more complete preflight each time I leave the aircraft will help me identify these problems prior to a flight.

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Original NASA ASRS Text

Title: CARGO ACFT HAS DOOR OPEN INDICATION ON TKOF ROLL. ABORTS CHK OF DOORS, LIGHT OUT. SECOND TKOF DOOR BLOWS OPEN.

Narrative: IMMEDIATELY AFTER GEAR UP FROM TKOF FROM 10L, THE R SIDE CABIN CREW DOOR CAME OPEN CAUSING THE FO AND MYSELF TO BRING THE ACFT AROUND FOR AN UNEVENTFUL LNDG TO 10L. THE MAJORITY OF THE PREFLT, INCLUDING THE WALK AROUND HAD BEEN COMPLETED BY MYSELF. NOTHING UNUSUAL HAD BEEN NOTED ON THE MDT. THE CABIN DOOR THAT CAME OPEN WAS THE R SIDE FUSELAGE FORWARD OF WING AND PROP. IT'S A DOOR THAT, IN OUR OP, IS NEVER USED BECAUSE THE CREW ENTERS FROM A HYD DOOR ON L SIDE. IFR CLRNC HAD BEEN RECEIVED FOR OUR 45 MIN FLT TO SEA AND AFTER FREIGHT WAS LOADED AND CARGO DOOR CLOSED, WE STARTED AND TAXIED OUT WITH NO UNUSUAL INDICATIONS. THE DOOR LIGHT CHK HAD BEEN COMPLETED IMMEDIATELY BEFORE STARTING AND ALL INDICATIONS WERE NORMAL. OUR FIRST TKOF ATTEMPT WAS ABORTED ON MY DECISION BECAUSE AT APPROX 80 KTS, OUR DOOR OPEN LIGHT BEGAN FLICKERING. UPON EXITING THE RWY, THE LIGHT EXTINGUISHED AND STAYED EXTINGUISHED. ON THE TAXI BACK, I STOPPED THE ACFT AND CHKED THE ENTRY DOOR WE USE SINCE THAT'S THE ONLY DOOR I DIDN'T PERSONALLY CLOSE. THE ENTRY DOOR WAS OPENED AND RELATCHED AND A LOOK AT THE DOOR IN QUESTION SHOWED HANDLE IN TRAIL, WHICH WAS THE INDICATION TO ME THAT THE DOOR WAS LATCHED. ANOTHER TKOF CLRNC WAS RECEIVED AFTER ANOTHER SUCCESSFUL DOOR LIGHT TEST. THIS TKOF ROLL WAS ALL NORMAL THROUGH ROTATION AND IMMEDIATELY AFTER GEAR UP AND LOCKED THE DOOR BLEW OPEN. THE CLAM SHELL DOOR, HINGED FROM THE TOP CONTINUED TO 'FLY' AS WE BROUGHT THE ACFT AROUND FOR LNDG ON 10L. WE RETURNED TO OUR RAMP AND SHUT DOWN TO DETERMINE THE CAUSE. MY OBSERVATION SHOWED NO DAMAGE TO THE DOOR AND WE COULD FIND NO MALFUNCTION WITH THE LOCKING MECHANISM. THE MICROSWITCH WAS FOUND TO BE DIRTY BECAUSE OF THE LACK OF ACTIVITY ON THE DOOR. AFTER PERSONALLY CLOSING AND LOCKING THE DOOR, THE FLT WAS CONTINUED WITHOUT INCIDENT. IN MY FURTHER INVESTIGATION, THE NEXT MORNING, I FOUND OUT A FUELER HAD GAINED ENTRY THROUGH THE DOOR IN QUESTION BECAUSE HE DIDN'T KNOW HOW TO OPERATE THE HYD DOOR HE LEFT A FUEL SLIP IN THE COCKPIT AND, UPON EXITING, HE INCORRECTLY CLOSED THE DOOR. WITH THE MECHANICAL LATCHES IN QUESTION, IT'S POSSIBLE FOR THE DOOR TO APPEAR CLOSED AND LATCHED. THE LATCHING MECHANISM WASN'T FULLY LATCHED BUT JUST PARTIALLY LATCHED. AT APPROX 140 KTS AFTER TKOF, THE FORCE WAS ENOUGH TO PULL THE HOOKS OFF THE LATCHES AND LET THE DOOR BLOW OPEN. A SIMPLE RELATCHING OF THE DOOR ON MY PART WOULD HAVE ILLUMINATED THIS INCIDENT. BECAUSE THE 'SVC DOOR' IS NEVER USED, CREW MEMBERS TEND TO TAKE FOR GRANTED THE PROPER LATCHING OF THE DOOR. A MORE COMPLETE PREFLT EACH TIME I LEAVE THE ACFT WILL HELP ME IDENT THESE PROBLEMS PRIOR TO A FLT.

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.