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Coriolis g’s passive ’tiltrotor’ transition

Posted: 4th Apr 2020

A radical tilt engine design may simplify eVTOL system designs.

Coriolis g Corps’ new approach as flight tested in their Vogi 1 model decouples the tilt of the thrusters from the fixed-wing frame, allowing independent pitch of the two sub-systems relative to each other. The decoupling results in naturally stable transitions and the continuous use of the rotors for hover as well as forward winged flight. The system can be considered as a tilting quadrotor passively coupled to a winged airframe via a swivel mechanism.

Vogi 1 model

This aircraft is capable of hover as well as efficient forward winged flight. The passive coupling system delivers seamless and continuous transition, allowing a simple and robust controller to operate all flight modes.

In the words of Coriolis g’s white paper “Pitch-Decoupled Tilt-Rotor Aircraft with Continuously Variable Transition“:

Pitch-decoupled tilt rotor free body diagram

“We propose a system that decouples the pitch rotation of the thrusters from the fixed wing frame thus allowing independent pitch rotation of the two airframes relative to each other. By decoupling the pitch frames of the two ’aircraft’ we can transition from VTOL to FW flight in a naturally stable manner and furthermore use the vertical thrusters as forward thrusters during winged flight. By decoupling the two stable systems we alleviate the risk of instability during transition and improve recovery from failure modes. The design also has a reduced number of moving parts and would be much easier to maintain than other tilt-rotor solutions considered to date. Although it may be classified as tilt rotor system, the dynamic and operational characteristics are sufficiently different from the traditional actuated Tilt Rotor and this new approach is hereby classified as a new Pitch-Decoupled Tilt Rotor or alternatively Passively-Coupled Tilt Rotor.

Taken from Coriolis g’s white paper

“Our successful continuous and seamless transitions to and from hover and fixed wing flight using this approach represents a dramatic departure from all of the four existing categories of traditional VTOL hybrid systems. Functional prototypes of the proposed system have been built and successfully flown proving that this new approach can flawlessly transition from both modes of flight as well as maintain stability and control throughout all intermediate configurations while attaining vertical takeoff and landing as well as winged flight.”


Opinion

A fascinating piece of smart thinking and demonstrated technology which could answer the eVTOL requirement with fewer and less complex systems, and therefore reduced weight. And in aerospace weight is king, in EA doubly so with the current levels of energy density and storage technology.

As for relying on simple mechanical joints for mission critical performance – that’s what helicopters do, through the mast and swashplate.

It will be interesting to see whose designs the technology appears on first – or who just straight out buys Coriolis g to deny it to their competitors.