Cessna 402/402C/B379 Businessliner/Utiliner
Flight Crew Air Transport Pilot (ATP)
Distraction; Training / Qualification
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Fuel Issue
Flight Crew Returned To Departure Airport; Flight Crew Took Evasive Action
Human Factors
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.
A C402 Captain returned to the departure airport after takeoff when he discovered the left fuel cap was unsecured.