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.
To understand how this Blainjett propulsion system works – and before anyone asks, no, these guys are no relation to me – you first need to understand how the swashplate and cyclic controls work to distribute thrust as a helicopter’s top rotor spins. Each blade can vary its pitch independently, with the height of the swashplate determining the pitch. With the swashplate sitting flat, pushing the whole thing up and down will change the pitch of all the blades at once.
But with the cyclic control, helicopter pilots are able to tilt the swashplate. Pushing the stick forward, for example, tilts it such that the blades gradually tilt as they spin around, getting flatter as they pass the front of the aircraft, then pitching up to develop more lift as they go around the back. The result is an asymmetry in lift, with more at the back of the disc, and the aircraft pitches forward and accelerates in that direction. The cyclic control can do this in any direction; it’s part of what makes helicopters such dynamic aircraft.