Narrative:

Normal takeoff from ZZZ. Immediately after gear retraction, the flight attendant called the flight deck. He stated he heard a 'banging' from the aircraft, but it had stopped. On this aircraft, a banging immediately after takeoff is almost always caused by an unsecured fuel cap. The banging usually continues until the flight completes, or the fuel cap breaks away from the aircraft. Since the banging stopped, I elected to continue to our destination. Upon selecting the gear down for landing, the flight attendant called and said the banging had resumed. Upon arrival at the gate, we observed the fuel door open, with the fuel cap still attached. This fuel cap had an unusually short chain. I surmise that with an unusually short chain, coupled with a change in airflow with the gear down, caused the cap to 'streamline' and not bang against the aircraft. A mechanic checked out the aircraft and noted 'no damage.' the cause of the fuel cap left off was the fueler not putting the cap back on after he completed fueling. A secondary cause was the short turn time at the outstation. By the time the fueler had completed fueling, the passenger were on board and the preflight inspection completed. The design of the ATR-72 makes a preflight inspection very difficult with passenger on board.

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Original NASA ASRS Text

Title: AN ATR72 WAS DISPATCHED IN NON COMPLIANCE WITH THE FUEL CAP NOT SECURED AND THE FUELING DOOR OPEN.

Narrative: NORMAL TKOF FROM ZZZ. IMMEDIATELY AFTER GEAR RETRACTION, THE FLT ATTENDANT CALLED THE FLT DECK. HE STATED HE HEARD A 'BANGING' FROM THE ACFT, BUT IT HAD STOPPED. ON THIS ACFT, A BANGING IMMEDIATELY AFTER TKOF IS ALMOST ALWAYS CAUSED BY AN UNSECURED FUEL CAP. THE BANGING USUALLY CONTINUES UNTIL THE FLT COMPLETES, OR THE FUEL CAP BREAKS AWAY FROM THE ACFT. SINCE THE BANGING STOPPED, I ELECTED TO CONTINUE TO OUR DEST. UPON SELECTING THE GEAR DOWN FOR LNDG, THE FLT ATTENDANT CALLED AND SAID THE BANGING HAD RESUMED. UPON ARR AT THE GATE, WE OBSERVED THE FUEL DOOR OPEN, WITH THE FUEL CAP STILL ATTACHED. THIS FUEL CAP HAD AN UNUSUALLY SHORT CHAIN. I SURMISE THAT WITH AN UNUSUALLY SHORT CHAIN, COUPLED WITH A CHANGE IN AIRFLOW WITH THE GEAR DOWN, CAUSED THE CAP TO 'STREAMLINE' AND NOT BANG AGAINST THE ACFT. A MECH CHKED OUT THE ACFT AND NOTED 'NO DAMAGE.' THE CAUSE OF THE FUEL CAP LEFT OFF WAS THE FUELER NOT PUTTING THE CAP BACK ON AFTER HE COMPLETED FUELING. A SECONDARY CAUSE WAS THE SHORT TURN TIME AT THE OUTSTATION. BY THE TIME THE FUELER HAD COMPLETED FUELING, THE PAX WERE ON BOARD AND THE PREFLT INSPECTION COMPLETED. THE DESIGN OF THE ATR-72 MAKES A PREFLT INSPECTION VERY DIFFICULT WITH PAX ON BOARD.

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.