Design optimization of Gamera II: A human powered helicopter

In pursuit of the Sikorsky Prize, two human powered helicopters have been designed by a team of students from the University of Maryland. Significant experience was gained from the construction and flight testing of the first helicopter, Gamera I. This experience led into design optimization and refinement of the second-generation vehicle, Gamera II, presented in this paper. Human performance over short periods of time was studied to characterize the power available, and the transmission was designed to deliver as much of this power as possible to the rotors. The addition of a hand-cranking mechanism was shown to increase pilot power output by 20% for the intended 60 second duration. The quad-rotor configuration was continued in Gamera II because it was shown to provide passive stability in ground effect. Innovative lightweight structural concepts were developed, which helped reduce vehicle empty weight by 33% to 32.3 kg (71 lb). The rotors were designed using a comprehensive optimization process that coupled aerodynamics, blade spar stiffness, and airframe weight models to yield the lowest possible vehicle power required. Power required to hover is predicted to have been reduced by 35% compared to Gamera I, enabling the 60 second flight endurance required as part of the Sikorsky prize. Flight testing of Gamera II is scheduled for summer 2012.