TY JOUR TI Economic Assessment of the Effect of Longitudinal Autopilot Controller Tuning on Airline Operating Costs KW economic assessment KW operating costs KW automated control system KW longitudinal channel KW PID controller KW optimization KW fuel efficiency KW actuators KW aircraft downtime KW net present value JO Journal of Applied Research AU Sokolov, O.A. AU Ivanov, I.A. AU Kopilov, K.S. PY 2026 IS 0 PB ITBO University