Narrative:

After receiving the release for our return flight to las; we asked the fueler to fuel the aircraft to the planned fuel of 2800 pounds. When the fueling process was complete; a thorough walkaround was completed by the first officer; then the boarding of our single passenger commenced. We conducted the before start checklist; indicating that the fuel caps were indeed in place and appeared to be securely in place. The flight to las was relatively uneventful; except for our request for a higher altitude due to moderate; continuous turbulence. Fuel balance was monitored and found to be equal throughout the flight. Upon landing in las; the first officer conducted his postflt examination of the aircraft and he and the fueler simultaneously found the right main fuel cap to be missing. After searching for a moment around the aircraft; operations was immediately notified. The first officer assured me that the right main fuel cap was in fact there prior to departure. I then contacted the a&P who does our fueling in ZZZ. I had asked him if he remembers anything unique about the fueling process; because we landed in las without a fuel cap. He adamantly stated that he was sure he placed the fuel cap on; stating he has been doing this as an a&P for yrs. When I asked him further; he said that he remembers that the fuel cap appeared to be worn. He also mentioned that the fuel cap had no chain attached to it. He remembered this because he took the cap off to fuel; placing it on the top of the wing; and the wind (ASOS XA42Z wind 320 degrees at 24 KTS gusting to 32 KTS; 10 SM visibility; clear) trying to blow it off many times. I had asked him to return to the ramp area; inspect the taxiway and runway we took off from; looking for any possible evidence of a fuel cap falling off prior to flight. He did so; calling me back approximately 1 hour later saying that he had inspected every inch of the airport; and found no evidence. He again stated to me unequivocally that he remembered securing the fuel cap.

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Original NASA ASRS Text

Title: BE1900 FUEL CAP WAS MISSING AFTER THE CONCLUSION OF THE FLT.

Narrative: AFTER RECEIVING THE RELEASE FOR OUR RETURN FLT TO LAS; WE ASKED THE FUELER TO FUEL THE ACFT TO THE PLANNED FUEL OF 2800 LBS. WHEN THE FUELING PROCESS WAS COMPLETE; A THOROUGH WALKAROUND WAS COMPLETED BY THE FO; THEN THE BOARDING OF OUR SINGLE PAX COMMENCED. WE CONDUCTED THE BEFORE START CHKLIST; INDICATING THAT THE FUEL CAPS WERE INDEED IN PLACE AND APPEARED TO BE SECURELY IN PLACE. THE FLT TO LAS WAS RELATIVELY UNEVENTFUL; EXCEPT FOR OUR REQUEST FOR A HIGHER ALT DUE TO MODERATE; CONTINUOUS TURB. FUEL BAL WAS MONITORED AND FOUND TO BE EQUAL THROUGHOUT THE FLT. UPON LNDG IN LAS; THE FO CONDUCTED HIS POSTFLT EXAM OF THE ACFT AND HE AND THE FUELER SIMULTANEOUSLY FOUND THE R MAIN FUEL CAP TO BE MISSING. AFTER SEARCHING FOR A MOMENT AROUND THE ACFT; OPS WAS IMMEDIATELY NOTIFIED. THE FO ASSURED ME THAT THE R MAIN FUEL CAP WAS IN FACT THERE PRIOR TO DEP. I THEN CONTACTED THE A&P WHO DOES OUR FUELING IN ZZZ. I HAD ASKED HIM IF HE REMEMBERS ANYTHING UNIQUE ABOUT THE FUELING PROCESS; BECAUSE WE LANDED IN LAS WITHOUT A FUEL CAP. HE ADAMANTLY STATED THAT HE WAS SURE HE PLACED THE FUEL CAP ON; STATING HE HAS BEEN DOING THIS AS AN A&P FOR YRS. WHEN I ASKED HIM FURTHER; HE SAID THAT HE REMEMBERS THAT THE FUEL CAP APPEARED TO BE WORN. HE ALSO MENTIONED THAT THE FUEL CAP HAD NO CHAIN ATTACHED TO IT. HE REMEMBERED THIS BECAUSE HE TOOK THE CAP OFF TO FUEL; PLACING IT ON THE TOP OF THE WING; AND THE WIND (ASOS XA42Z WIND 320 DEGS AT 24 KTS GUSTING TO 32 KTS; 10 SM VISIBILITY; CLR) TRYING TO BLOW IT OFF MANY TIMES. I HAD ASKED HIM TO RETURN TO THE RAMP AREA; INSPECT THE TXWY AND RWY WE TOOK OFF FROM; LOOKING FOR ANY POSSIBLE EVIDENCE OF A FUEL CAP FALLING OFF PRIOR TO FLT. HE DID SO; CALLING ME BACK APPROX 1 HR LATER SAYING THAT HE HAD INSPECTED EVERY INCH OF THE ARPT; AND FOUND NO EVIDENCE. HE AGAIN STATED TO ME UNEQUIVOCALLY THAT HE REMEMBERED SECURING THE FUEL CAP.

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.