Air taxi flight crew reported a taxiway excursion from Taxiway LB going toward the ramp at TUL airport during night time operations. The crew reported poor lighting in that area as a contributing factor.
Synopsis
Air taxi flight crew reported a taxiway excursion from Taxiway LB going toward the ramp at TUL airport during night time operations. The crew reported poor lighting in that area as a contributing factor.
Narrative
I was taxiing and after landing 18L following our taxi clearance C; L; LB. On LB facing the ramp I saw the line guy at the far end of a line of orange cones extending out toward me. There was quite a bit of room north of the cones. I felt the furthest out cone was in play and it would be a tight fit if I continued further. I think I even vocalized my concern with the cones. With my focus there and coming around for the line guy; I turned left too early and went into the grass. It was dark and obviously didn't realize I was turning onto the grassy area. After realizing I was in the grass I saw only ramp and no obstacles in front of me and continued to the concrete.Cause: Darkness; obstacles; SA (Situational Awareness); no blue taxi way lighting on LB.Suggestions: Many non movement areas have no line guidance and self guidance is used. Like what we had to do at our departure airport. I thought I was in that regime. In looking at the scene afterward; I did have more taxi line to use. Should have used that in conjunction with my PNF for guidance against the cone hazard.
Second reporter narrative
While pulling into the ramp at night on Taxiway LB; my SIC made the decision to make an early left turn to not get too close to cones on the ramp. Unfortunately while he made that early turn; my head was down and I did not see him roll into the grass until it was too late. The aircraft rolled through the corner and continued on turn park in the ramp without any damage.My head was down; when I felt aircraft hop I knew something was off. When I looked up; I saw that my SIC had turn the aircraft into the grass without realizing it.Cause: Poor lighting conditions in that area of ramp.Suggestion: It may be a better idea to have the PIC stay in the left seat even while pilot monitoring. This would for the most part avoid these kind of issues.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.