Open-rotor

Horizon Aeronautics is prototyping an eVTOL hovercycle concept that uses a complex and interesting split-swashplate "Blainjett" variable pitch rotor system that only exposes half of each fan. Very odd, but Horizon says it's highly efficient.

GE Aviation and NASA will run a wind tunnel test program to evaluate and test counter-rotating fan-blade systems for open-rotor jet engine designs.