Narrative:

After departure; I noticed the left fuel cap was unsecured. I returned to the airport. I will be more diligent in physically making sure fuel caps; doors and panels are secure.

Google
 

Original NASA ASRS Text

Title: A C402 Captain returned to the departure airport after takeoff when he discovered the left fuel cap was unsecured.

Narrative: After departure; I noticed the left fuel cap was unsecured. I returned to the airport. I will be more diligent in physically making sure fuel caps; doors and panels are secure.

Data retrieved from NASA's ASRS site as of July 2013 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.