Narrative:

I was acting as a cfii on a local training flight that was planned for a total of 1.5 hours. Before takeoff student and I had company ground personnel fill the high winged small aircraft full of fuel. After the fuel attendants finished fueling, I got out and visually checked the caps. Both fuel caps looked flush and aerodynamic from the front of the airplane. We then started the engine and got clearance to taxi to runway 27. The fuel vent was venting fuel as it sometimes does when the tanks are very full. The run up went well, then we got clearance to takeoff from tower. Just after liftoff the airport manager called to the tower (on tower frequency) that the airplane that took off on 27 was losing fuel. My student remained in the pattern and then landed. My student and I never visually saw any fuel discharge except for the fuel vent. After landing I got out and this time stood on the wing strut and found the aft part of the fuel cap to be lifted above the locked position. I then closed the cap proper and we completed the training. From visual inspection on the ground (my height 73 inches) both fuel caps looked to be secure. The leading edge of both caps was flush with the top of the wing and the hand grip of the cap was aerodynamic, that is, it was streamline with the air flow. Always physically check the caps -- not just visually.

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Original NASA ASRS Text

Title: A RETURN LAND MANDATED AFTER TWR CTLR INFORMS SMA PLTS THAT FUEL IS VENTING FROM WINGS ON TKOF.

Narrative: I WAS ACTING AS A CFII ON A LCL TRAINING FLT THAT WAS PLANNED FOR A TOTAL OF 1.5 HRS. BEFORE TKOF STUDENT AND I HAD CGP FILL THE HIGH WINGED SMA FULL OF FUEL. AFTER THE FUEL ATTENDANTS FINISHED FUELING, I GOT OUT AND VISUALLY CHKED THE CAPS. BOTH FUEL CAPS LOOKED FLUSH AND AERODYNAMIC FROM THE FRONT OF THE AIRPLANE. WE THEN STARTED THE ENG AND GOT CLRNC TO TAXI TO RWY 27. THE FUEL VENT WAS VENTING FUEL AS IT SOMETIMES DOES WHEN THE TANKS ARE VERY FULL. THE RUN UP WENT WELL, THEN WE GOT CLRNC TO TKOF FROM TWR. JUST AFTER LIFTOFF THE ARPT MGR CALLED TO THE TWR (ON TWR FREQ) THAT THE AIRPLANE THAT TOOK OFF ON 27 WAS LOSING FUEL. MY STUDENT REMAINED IN THE PATTERN AND THEN LANDED. MY STUDENT AND I NEVER VISUALLY SAW ANY FUEL DISCHARGE EXCEPT FOR THE FUEL VENT. AFTER LNDG I GOT OUT AND THIS TIME STOOD ON THE WING STRUT AND FOUND THE AFT PART OF THE FUEL CAP TO BE LIFTED ABOVE THE LOCKED POS. I THEN CLOSED THE CAP PROPER AND WE COMPLETED THE TRAINING. FROM VISUAL INSPECTION ON THE GND (MY HEIGHT 73 INCHES) BOTH FUEL CAPS LOOKED TO BE SECURE. THE LEADING EDGE OF BOTH CAPS WAS FLUSH WITH THE TOP OF THE WING AND THE HAND GRIP OF THE CAP WAS AERODYNAMIC, THAT IS, IT WAS STREAMLINE WITH THE AIR FLOW. ALWAYS PHYSICALLY CHK THE CAPS -- NOT JUST VISUALLY.

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.