Tilt-wing aircraft control

April 3, 2019

With the latest developments in hybrid electric propulsion technology, and the energy and focus on innovation from EASA and other aviation regulatory bodies in the last two years, there has never been a more exciting time to be developing a new aircraft.

We’ve previously talked about our vision for Regional Air Mobility: typically journeys between 25 and 800km. Dufour Aerospace is developing the aEro family of long range, high speed, hybrid electric VTOL aircraft specifically to address this market. Tilt-wing aircraft offer the best combination of hover capability and cruise efficiency.

Tilt-wing aircraft have been successfully tested for many decades. For example, the Canadair CL-84 received positive reviews from over 40 pilots during its intensive test programme in the ’60s and ’70s, including carrier operations in gale storm conditions. And the tilt-rotor V-22 Osprey (an aerodynamically less efficient cousin of the tilt-wing (1)) has proven its reliability in harsh environmental conditions over 30 years and 450,000 flight hours.

In 2016 we built and flew one of the world’s first electric aerobatic planes, aEro 1. Our experience in electric propulsion technology has allowed us to modernise the tilt-wing aerodynamic concept, increasing system safety and reliability and decreasing total weight and cost. The next step was then to develop a set of flight control laws to maximise comfort and simplicity.

We have been working with David Rohr and the ETH Autonomous Systems Lab to demonstrate high-level control of a scale model tilt-wing aircraft. We’re very proud of his work and the results he has recently published.

Trim maps

A particular challenge of tilt-wing control is the highly non-linear and even non-continuous trim requirements in different modes of flight. David developed trim maps to handle this by carefully identifying and modelling the aerodynamic system, searching for stable solutions in the model, smoothing the resulting maps, and then verifying on the real system. He then went on to develop a high-level “cruise control” operational mode, where the pilot can simply command forward and vertical speeds, which are mapped automatically to actuations of control surfaces, wing tilt and throttles.

Demonstrating performance across a range of manoeuvres

This video of the work shows the degree of stability we can achieve throughout the flight envelope and the conversion corridor between helicopter and airplane modes. You can clearly see that the airflow remains laminar around the wing at all airspeeds, resulting in smooth and stable flight and ultimately passenger comfort.

We anticipate that the launch of our aEro family of fast, efficient, and quiet tilt-wing VTOL aircraft will inspire a new generation of pilots to take flight. Simplified vehicle operation is an important element of our strategy to ensure that these aircraft maintain an excellent standard of safety, even as we scale up to airline traffic volumes. It ensures predictable and stable aircraft behaviour during vertical take-off and landing (VTOL), and if necessary, during short-field or conventional runway take-off and landing (STOL or CTOL), maximising the options available to the pilot in addition to the airframe parachute in case of emergency.

Our aircraft will also carry an array of sophisticated sensors and assistance features to significantly reduce pilot workload, and ultimately enable autonomous flight. We are working with our partner Daedalean to prepare for this goal.

At Dufour Aerospace, we are at the forefront of the Vertical Mobility revolution, and we want to help as many people as possible enjoy this exciting new form of flight, either as a passenger or as a pilot themselves. Please get in touch if you share our excitement, and want to join us in our mission to bring people together.

(1) W. F. Chana and T. M Sullivan, “The Tilt Wing Configuration for High Speed VSTOL Aircraft”

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With over 30 years of experience in Swiss commercial helicopter operations, we understand the real world requirements of VTOL aircraft. Our engineering team with years of aircraft construction experience is building aircrafts for rugged operations in harsh environments. Our patented combination of proven aerodynamic concepts with the latest technology makes our aircraft rock solid with unparalleled performance.