Optimal Cruise Airspeed for Hybrid-Electric and Electric Aircraft: Applications to Air Mobility

Electric and hybrid-electric aircraft can help our society transition towards more sustainable aviation and lower greenhouse gas (GHG) emissions. This paper finds the speed that minimizes the direct operating cost (DOC) for hybrid-electric aircraft. The solution is the positive real root of a quintic polynomial which is derived using Pontryagin’s minimum principle. By properly selecting a hybridization factor, one can also find the cruise airspeed corresponding to the minimum DOC of an electric aircraft. The optimal airspeed is integrated into the Rapidly-exploring Random Trees Star (RRT*) path planning algorithm. The minimum DOC solutions are investigated in a hybrid-electric international travel scenario and the path planning approach is applied to an electric aircraft city scenario.