While there were several novel designs in the DARPA lift challenge, in the end the winners by a large margin were helicopter and a quadcoptor designs which reached close to 1:4 payload ratio.
Both electric or gas engine designs did equally well.
The most interesting part was watching the failure modes: main helicoptor rotors snapping under
payload weight, wind gusts sending quadcoptor controls into an uncontrollable regime. Batteries and electric motors heating up under load stress.
The most interesting part was watching the failure modes: main helicoptor rotors snapping under payload weight, wind gusts sending quadcoptor controls into an uncontrollable regime. Batteries and electric motors heating up under load stress.