An entirely new way to fly

The cyclorotor concept offers several potential advantages in comparison to traditional vertical takeoff and landing or fixed wing air vehicles. The rotating wing creates lift and thrust when the blades move backward with respect to the vehicle's direction of flight. Furthermore, the rotation speed and pitching of the cyclorotor do not need to increase with vehicle speed.

Such propulsion systems could not be commercially implemented as the technology and analytical tools needed to analyse the complex flow created between the pitching rotating blades was lacking. Recent advancements in the technology open the possibility of introducing the cyclorotor concept in the aeronautical industry.

A multidisciplinary research team from five European countries worked to demonstrate this propulsion system. This would enable air vehicles to take off like a helicopter and fly at high speeds like aircraft. The CROP (Cycloidal rotor optimized for propulsion) project was funded with more than half a million Euros by the European Commission.

Since the main aerodynamic component of a cyclorotor is a pitching aerofoil, flow control techniques that could deal with stalled flow were beneficial. CROP team examined several flow control mechanisms and different rotor assemblies, with a six-bladed configuration achieving the greatest efficiency. Furthermore, they have studied a rotor assembly that allows the integration of a plasma actuator.

Specifically, CROP project partners showed the combined effect of a leading edge vortex and what is called plasma-enhanced cycloidal thruster using computational fluid dynamics models and numerical analysis. To achieve a lower weight-to-power ratio, the integration of a low-weight electric drive train into the system was explored.

By the end of the project, CROP optimised a four-rotor lab model and demonstrated proof-of-concept for an electrically powered cyclogyro. The new propulsion system minimises fuel consumption and increases aircraft manoeuvrability. This breakthrough concept is leading the way to innovative air vehicle designs with improved performances and reduced environmental impact.

CROP has laid the foundations for greener transport in the near future, and its results are in line with the objectives set by the Advisory Council for Aviation Research and Innovation in Europe (ACARE).