CROP Project Newsletter Q2/2015
Project final report
After two years of fruitful research and cooperation, the CROP project has come to an end. We are proud to present you the main achievements of the project, which brought the CROP concept to a higher level of a technology readiness. A future of green, efficient and compact propulsion in innovative vehicles seems now closer.
Final project videos on YouTube:
YouTube Video
YouTube Video
2.1 Intermediate meeting – April 2014 @ University of Sheffield, UK
The intermediate CROP technical meeting took place at the University of Sheffield on April 28th – 29th 2014 and was organised by Prof. Geraint Jewell and Dr. Leon Rodrigues. The talks featured many important advances on system modelling, CFD and CSD analyses, vehicle integration, experimental testing, implementation of electric drives and technology evaluation. As a final result, the roadmap for the final project term was outlined by the consortium members, in a collaborative and enthusiast atmosphere.
The University of Sheffield
Final technical meeting and public presentation of final results – December 2014 @ ERC Executive Council HQ, Covent Garden, Brussels
The final meeting of project CROP coincided with a conclusive event, in which all the results and activities of the project have been presented by the partners and reviewed by the former Project Officer (PO) Dr. Eric Lecomte. A public presentation followed, in which Project Coordinator Prof. José Pàscoa outlined the main achievements of CROP in front of an audience which comprised the new PO Dr. Christiane Bruynooghe.
Public presentation of final results
Review of research results and highlights
CROP-propelled aerial systems

The integration of cycloidal rotors in innovative, green vehicles was the subject of a consistent share of the project activities. Four different configurations were taken into consideration:

UNIMORE proposed the concept of a large-scale, high-altitude airship propelled by four quad-cycloidal rotors, whose envelope is characterized by a large, almost flat surface that can host specifically designed photovoltaic modules which provide full energy supply. Such a vehicle could cruise at an operative velocity of 20 m/s, sustaining a commercial payload of 5000 kg, at an operative altitude of 2 km, providing approximately 2000 flight hours per year at 45° of latitude.
UNIMORE airship concept
GROB envisaged the integration of cyclogyros in a more conventional ultralight two-seater aircraft, with rotors placed midwing. The adoption of cyclorotors should endow the aircraft with Short Take-off and Landing (STOL) capability; the large wingspan should ensure a greater efficiency in forward flight.
GROB's ultralight tandem seater
POLIMI studied the gradual introduction of the cyclorotor as a secondary propulsion mean of helicopters, proposing three different variants of a hybrid rotorcraft which was named the heligyro, the most viable of which is a helicopter in which the tail rotor is replaced with two cycloidal rotors. The cyclorotors partially relieve the main rotor of the need to provide thrust and control of roll and yaw, while the main rotor, being more efficient in hovering, provides the necessary lift.
POLIMI's heligyro
IAT21 proposed the innovative D-DALUS vehicle, in both manned and unmanned configurations. Such a vehicle is supposed to be propelled by either fully electric and hybrid engines, and is expected to be capable of vertical take-off and landing (VTOL) and to be extremely manoeuvrable and stable. Propulsion is provided solely by cycloidal rotors (four in the preliminary design).
IAT-21 D-DALUS two-seater
System design and implementation

The overall design and implementation of the PECyT needed a consistent and reliable theoretical framework to be set up to operate at system level, and some key technological issues to be tackled. In particular:

  • Three different mathematical models of the cycloidal rotor kinematics and dynamics (UBI, POLIMI, UNIMORE), were defined and successfully validated against the experimental data provided by IAT21 and further available literature. All models served slightly different purposes: the model of UBI allows for a complete kinematic analysis and parametric design of a cyclorotor; the model of POLIMI included forward flight conditions and was used to perform an aeroelastic analysis and an analysis of rotor stability at different flight regimes; the UNIMORE model was employed to define a theoretically optimal pitching schedule.
  • A further analytical model was defined by USFD for the design and sizing of electric drives and gearbox of a cyclorotor.
  • The effects of single and multi-DBD (Dielectric Barrier Discharge) on the performance of the PECyT (Plasma-Enhanced Cycloidal Thruster) were analysed by UBI, and optimal control strategies for plasma actuation in cyclorotors were defined. Theoretical results indicate that the increase in vertical lift due to the plasma actuation exceeds 5%.
  • An innovative class of rotating transformers for the delivery of the high voltage (required for DBD) to the rotor blades without the need of wirings was devised by USFD. The main advantage of a rotating transformer is that the frequency is independent of rotating speed. It also does not require magnets for excitation; it is of smaller size and can have a controlled or fixed excitation in the stator frame. This makes it a simple and robust solution for a cyclorotor application.
validation of analytic models, rotating transformer
System simulation
Computational fluid (CFD) and solid (CSD) dynamics as well as multiphysics simulation tools were extensively employed to dig deeper into the structural and aerodynamic behaviour of a cycloidal rotor, and the effects of the inclusion of DBD:
  • Three 2D and two 3D CFD models of cyclorotors were set up by UBI, POLIMI and UNIMORE, with both Reynolds-Averaged Navier-Stokes (RANS) turbulence modelling or inviscid conditions and actuator disks, using both commercial and open-source software. All models exploited dynamic mesh capabilities to reproduce the cycloidal pitching of the blades, and were validated and/or tuned according to experimental data.
  • A multiphysics model including the effect of single- and multi-DBD plasma actuators was set up by UBI to investigate the effect of unsteady and steady DBD actuation on the aerodynamic performance of a pitching airfoil. Major findings include a visible reduction of the separation bubble during the downstroke half-cycle and a delay of stall during the upstroke phase.
  • A flexible wing multibody model was set up by POLIMI to study the stability of the rotor and the consequence of blade inflection on the overall performance.
  • A study of the influence of several geometrical parameters on the cyclorotor aerodynamics was carried out by UBI, and the most efficient configuration in terms of power loading (thrust/power) in hovering conditions was found as a function of blade profile, rotor solidity, chord-to-radius ratio and pitching axis location.
  • UNIMORE used its CFD model to perform a preliminary assessment the performance of the cyclorotor in forward flight conditions and found an optimum value of the rotor advance ratio exists between 0.5 and 1, for which the power loading is maximum.
  • POLIMI exploited its multibody CSD and CFD models to investigate the effect of blade flexibility and the effect of endplates on the rotor efficiency and stability. It was found that the inflection of blades reduces the efficiency but does not impair stability, while the presence of endplates seemingly improves the efficiency by canalizing the flow.
  • CFD was used by UNIMORE also to assess the aerodynamic behaviour of the airship and GROB's tandem seat cockpit aircraft vehicle concepts. It was found that the airship concept has a very efficient design and that the inclusion of cyclorotors as propulsion means does not affect the aerodynamic performance. Furthermore, the presence of a leading edge in front of the rotor in the ultralight aircraft was seen to possibly increase the rotor efficiency.
  • The heligyro concept was verified by POLIMI with their analytical model. An optimal geometric configuration was singled out for the cyclorotors to replace the original thrust and moment provided by the tail rotor. The resulting power requirements were in line with those of the traditional helicopters, hence indicating that the concept is indeed promising.
influence of blade profiles on power loading
validation of analytic models, rotating transformer
Experimental testing
Experimental testing was carried out entirely by IAT21 and focused on the cyclorotor configurations which were devised for inclusion on the D-DALUS aircraft. Two different tests were carried out:
  • A six-blade, 1.2 m diameter rotor was tested in the wind tunnel of the TUM (Technical University of Munich) to determine the thrust and power delivered at different rotating speeds in hovering conditions.
  • A full-scale model of the unmanned D-DALUS aircraft, complete with four cyclorotors, was tested in the same wind tunnel. Results provided by IAT21 indicate that thrust efficiency increases with forward speed, making the proposed vehicle concept a very interesting and competitive alternative to traditional helicopters.
D-Dalus model, wind tunnel testing
Results and achievements of the CROP project were presented at a remarkable number of conferences and industrial events throughout 2014:
  • Presentation at the Austrian Chamber of Commerce (WKŐ) Washington Embassy (USA), 21-23 Jan 2014
  • Internationale Luft- und Raumfahrtausstellung (ILA), Berlin, Germany,
    20-24 May 2014
  • 70th Annual Forum and Technology Display, Montreal, Canada, 20-22 May 2014
  • 44th AIAA Fluid Dynamics Conference, Atlanta, Georgia, 16-2 June 2014
  • 6th. European Conference on Computational Fluid Dynamics, Barcelona, Spain, July 2014
  • 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, USA, July 2014
  • 40th European Rotorcraft Forum, Southampton, UK, 2-5 Sep 2014
  • SAE 2014 Aerospace Systems and Technology Conference, Cincinnati, OH, USA
  • 4th EASN workshop on Flight Physics and Aircraft Design, Aachen, October 2014 (with one workshop session entirely dedicated to CROP)
  • 9th AIRTEC Conference Frankfurt – 28 Oct 2014
  • ASME International mechanical engineering congress and exposition, IMECE 2014, Montreal, Quebec, Canada, November 2014
EASN workshop
List of Publications
L. Gagnon, M. Morandini, G. Quaranta, P. Masarati, "Cyclogyro Thrust Vectoring for Anti-Torque and Control of Helicopters" AHS 70th Annual Forum and Technology Display, Montreal, Canada, May 20-22, 2014.
C. M. Xisto, J. C. Páscoa, J. A. Leger, P. Masarati, G. Quaranta, M. Morandini, L. Gagnon, D. Wills, M. Schwaiger, "Numerical Modelling of 3D Geometrical Effects in the Performance of a Cycloidal Rotor", 6th European Conference on Computational Fluid Dynamics (ECFD VI), Barcelona, Spain, July 20-25, 2014.
C. M. Xisto, J. C. Páscoa, M. Abdollahzadeh, J. A. Leger, P. Masarati, L. Gagnon, M. Schwaiger, D. Wills, "PECyT - Plasma Enhanced Cycloidal Thruster", Propulsion and Energy Forum 2014, Cleveland, OH, July 28-30, 2014, doi:10.2514/6.2014-3854.
Leger J.A., Páscoa J.C., Xisto C.M., (2013) "Parametric design of cycloidal rotor thrusters", Proceedings of ASME 2013 International Mechanical Engineering Congress & Exposition, IMECE2013, November 15-21, San Diego, California USA.
Monteiro J. A., Páscoa J. C., Xisto C.M., (2013), "Analytical Modeling of a Cyclorotor in Forward Flight", in Proc. SAE Aerotech  2013, Montreal, Quebec, Canada Nº 2013-01-2271 doi:10.4271/2013-01-2271.
L. Gagnon, G. Quaranta, M. Morandini, P. Masarati, C. M. Xisto, J. C. Páscoa, "Fluid-Structure Interaction Analysis of a Cycloidal Rotor", 44th AIAA Fluid Dynamics Conference, Atlanta, Georgia, June 16 to 20, 2014.
L. Gagnon, M. Morandini, G. Quaranta, P. Masarati, G. Bindolino, J. C. Páscoa, C. M. Xisto, "Conceptual Design of a Cycloidal Rotor Solution for Propulsion and Control", 40th European Rotorcraft Forum 2014, Southampton, UK, September 2-5, 2014.
Trancossi, M., Dumas, A., Xisto, C. M., Páscoa, J. C., Andrisani, A. (2014), "Roto-Cycloid propelled airship dimensioning and energetic equilibrium" SAE 2014 Aerospace System and Technology Conference, Cincinnati, Ohio, USA, September 23-25, doi:10.4271/2014-01-2107.
Xisto, C. M., Páscoa, J. C., Leger, J. A., Gerlach, A., (2014), "Multi-Dielectric Barrier Discharge Plasma Actuator for Cycloidal Rotor Active Flow Control", 4th EASN Association International Workshop on Flight Physics and Aircraft Design, Aachen, Germany, October 27-29.
Leger, J. A., Páscoa, J. C., Xisto, C. M., (2014), "Aerodynamic Optimization of Cyclorotors", 4th EASN Association International Workshop on Flight Physics and Aircraft Design, Aachen, Germany, October 27-29.
A. Andrisani, D. Angeli, A. Dumas, "Optimal Pitching Schedules for a Cycloidal Rotor in Hovering", 4th EASN Association International Workshop on Flight Physics and Aircraft Design, Aachen, Germany, 27-29 October, 2014.
L. Gagnon, M. Morandini, G. Quaranta, P. Masarati, "Cycloidal Rotor Aerodynamic and Aeroelastic Analysis", 4th EASN Association International Workshop on Flight Physics and Aircraft Design, Aachen, Germany, 27-29 October, 2014.
"Efficiency Increase in Forward Flight Researched at Cyclogyro rotor VTOL Aircraft", October 2014.
M. Schwaiger, D. Will, S. Elflein: "D-Dalus VTOL - efficiency increase in forward flight", AEAT-12-2014-0205.
Leger A. J., Páscoa J. C., Xisto C. M., (2013) "Kinematic and Dynamic Parametric Analysis of Cycloidal Rotor Thrusters", Proceedings of ICEUBI 2013 - International Conference on Engineering, November 27-29, UBI, Covilhã, Portugal.
Leger J. A., Páscoa J. C., Xisto C. M., (2015) "Analytical Modeling of a Cyclorotor in Hovering State", accepted for publication in Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering. doi:10.1177/0954410015569285.
Project Consortium
Universidade da Beira Interior   Universidade da Beira Interior, Portugal
Università di Modena e Reggio Emilia   Università degli Studi di Modena e Reggio Emilia, Italy
IAT21 - Innovative Aeronautics Technologies GmbH   IAT21 - Innovative Aeronautics
Technologies GmbH, Austria
The University of Sheffield   The University of Sheffield, United Kingdom
Grob Aircraft AG   Grob Aircraft AG, Germany
Politecnico di Milano   Politecnico di Milano, Italy
Universidade da Beira Interior, Portugal
Prof. Dr. José Carlos Páscoa Marques
Convento de Santo Antonio
Covilha, Portugal
For more information about the CROP project, please visit:
The research leading to these results has received funding from the European Union Seventh Framework Programme [FP7/2007-2013] under grant agreement no. [323047]
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