An Engineering Study of Retrofitting a Piston Engine Powered Helicopter with Hydrogen Fuel Cells

Preliminary calculations are presented assessing the impact of using eVTOL technologies on a piston engine powered notional helicopter. A performance model is first developed to estimate the power requirements in hover, vertical climb, cruise, and loiter phases of the flight. Two eVTOL options are explored. First, the piston engine is replaced with twin electric motors powered by Lithium-ion batteries. It is found that the low energy density of the battery system would greatly increase the gross weight of the system for the original mission, although shorter air taxi and air ambulance missions would be feasible. Second, a liquid hydrogen fuel cell system is considered. This option allows the eVTOL configuration to meet the range and endurance of the baseline piston powered system with a small increase in the system weight. Preliminary estimates have also been made for the cost of operations in dollars per passenger per kilometer. The propose retrofits would cost below $1.50 per passenger-kilometer, making them economically competitive with piston engine aircraft and other eVTOL systems in development