Thierry Dubois is a freelance writer specializing in helicopters, business aviation and aerospace technology. He earned a degree in fluid dynamics from an engineering school in Toulouse, France in the mid-1990s. At an unexpected crossroads, he found his first job in journalism. In 1997, he started working for French aerospace weekly Air &amp; Cosmos in Paris. This lasted until 2000, when he moved south to Lyons. He then became a freelancer, working for various aerospace publications and has been part of the AIN team since late 2000. In addition to writing about business aviation, Thierry shares responsibility for the rotorcraft section. He also is a regular on-site writer for AIN’s daily editions at international airshows such as the Paris, Farnborough, Dubai and Singapore shows, as well as at EBACE in Geneva.
In 2007, he won the Honeywell award for “Best systems or technology submission” at the Aerospace journalist of the year awards. In 2013, he won an Aerospace Media Award for the "Best Safety, Training &amp; Simulation Submission."
In other activities, Thierry moderates international conferences on aviation technology topics. Thierry is married and has three children, who seem to begin enjoying the mountains–as their parents do.

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Thierry Dubois

A global team of research organizations is quietly working on an active rotor blade in which distributed piezo-electric actuators can change blade twist almost continuously over the course of one blade revolution. Partners can be found in the U.S., Europe and Asia. A full test campaign is scheduled for next year.


Joining forces are the U.S. Army, NASA, France’s Onera, Germany’s DLR, Korea’s Konkuk University and Aerospace research institute (Kari) and Japan’s Jaxa. The effort began in 2010, Blanche Demaret, Onera’s delegate director for rotorcraft, told AIN. It is known by the acronym Star, standing for smart twisting active rotor. It exploits a concept of actuator distribution over the blade originally conceived by DLR.


“A helicopter blade works as an airfoil in airflow running from the leading edge to the trailing edge for only a quarter of each revolution,” Demarets told AIN. For the remaining 75 percent of the revolution, it is subject to vortices and stalls, generating both noise and drag, respectively. In addition, the blade undergoes vibration transmitted from the main gearbox or created by the airflow.


“We are trying to act on these negative phenomena,” Demaret said. Piezo-electric actuators can be distributed over the surface of the blade to change twist. Other technologies, such as the one Eurocopter has dubbed <a href="http://www.ainonline.com/aviation-news/hai-convention-news/2010-02-20/edgy-new-blades-ease-eurocopter-noise-footprint">Blue Pulse</a>, use only trailing-edge flaps. In the Star project, Onera has been in charge of the closed-loop control. “Without any pilot input, the system will send actuating orders at a rate of 64 per second,” Demaret explained.


So what is this going to change for the crew? Nothing, in terms of piloting; the system should be “transparent.” The difference will be found elsewhere. “Any improvement to the main rotor has an impact on the helicopter’s entire performance,” Demaret said. Depending on the tradeoff the designers choose, they can make the helicopter faster or more fuel-efficient. Or they can reduce vibration and noise, or elect for a mix of all these.


Such an active rotor will run on a test rig next year. It will be installed at the large low-speed facility wind tunnel in Marknesse, Netherlands.


Even though this will be a major step in technology demonstration, Demaret remains conservative in making predictions about possible applications. “Sometimes it takes 10 years before a helicopter manufacturer is convinced and turns a technology into a product,” she said.


In an even more distant future, active blades might replace the swashplate, saving weight and complexity. The actuators could use plasma, vortex generators or pulsed air.

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