Eurocopter AS 350/355/EC130 - Astar/Twinstar/Ecureuil
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors
I flew a Part 91 ferry flight with the fuel cap off. After reviewing the logbook; I received a flight release and went out to preflight the aircraft. I did a final walk around and climbed into the cockpit. I checked the fuel and decided that I needed a few more gallons in order to land with the required amount to be mission ready. The aircraft was parked next to the fuel truck so I went in to ask about having the aircraft moved; but the pilot offered to drive the truck over and fuel the aircraft. I went back out and removed the fuel cap and placed it in the step with the key inserted. Once the truck was pulled up I received a phone call from the [manager] and the other pilot continued to fuel me. When he was done I thanked him; he got in the truck and repositioned it. At this point it was dark and I had just done a preflight and a final walk around in the last 10 minutes and now I was doing another final walk around. My thought was; I know that the aircraft is good but; I'm going to go through the motions. Unfortunately; I should have been thinking what has changed since I did my last walk around. On my final walk around; when I got around to the left side of the aircraft instead of doing my normal 22 point check of all handles and latches I just checked the engine and transmission latches and climbed in. Upon arrival I did a post flight and found the cap with the key installed in the step hole. I notified my Lead pilot and my [manager].In the future I will incorporate the fuel cap in my new 23 point walk around inspection and I will also always think about what has been touched or changed since I last looked at the aircraft and pay closer attention to those things.
EC-130 pilot reported departing with the fuel cap off.