Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Commercial
Flight Crew Last 90 Days 107; Flight Crew Total 6500; Flight Crew Type 350
Communication Breakdown; Distraction; Confusion; Fatigue; Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Excursion Ramp
Flight Crew Became Reoriented
Company Policy; Procedure; Weather; Airport
After flying the approach I taxied toward the FBO. I was planning on remaining away from the fuel island. The Marshaller was standing by but on the other side of the island (other side of bright light). With nonstandard lighted wand signals and with a yellow line I elected to circle the island to the right at a controlled speed. The right main gear exited the asphalt into the grass by a distance of 5 feet. Understanding the situation; engines were shut down and passengers deplaned with the door been on the left side and over asphalt. The past days had been rainy and the wheels were deep in the grass.That morning we picked up passengers and parked facing west away from the Fuel Island. We were marshalled in that position. That evening; in darkness and rain reducing visibility; the marshaller came on the side of the FBO planning on parking the plane facing North; but the signals (lighted wand) were confusing. With a yellow line in sight; I proceeded around the Island. This line was a marking for refueling purpose. It had all the characteristic of a taxiway centerline. At no time did the Marshaller prevent us from making forward motion.A better study of the layout and briefing for the taxi portion of the flight would have alleviated the risk experienced. The yellow line was confusing. Double red line would be more appropriate for the protection of the fueling area.
Air Taxi Captain reported a ramp excursion due to confusing Marshaller instructions and taxiway markings.