The First Successful Flight of the Distributed Propulsion Aircraft Model

DECOL, birth of a cross-cutting collaborative research project

The drone, named DECOL for DEmonstrateur COntrôle Latérale (Lateral Control Demonstrator), was equipped with eight 1,200-watt (W) electric motors. It followed a precise flight plan and tested more than 70 flight parameters. This protocol was used to check the take-off, landing and stalling speeds, and to validate the measurement and control systems. This first flight was a major step forward in the development of this demonstrator with its 2-meter wingspan.

It all began on the Institute’s Campus.
DECOL was born of the desire of the teams at the Aerospace Vehicles Design and Control Department (DCAS) to develop a flying demonstrator activity. Flight experimentation on airplane models is part of this department’s research work on new configurations for electrical propulsion aircraft. The choices were made based on the production capacities and the expertise of various research departments among the technical teams at ISAE-SUPAERO. The demonstrator’s wings and empennage were made of a carbon composite at the workshop Mechanics of Structures and Materials Department (DMSM), while the carbon and wood fuselage part and the final assembly took place at the prototyping area – InnovSpace (Fablab). The teams at the Complex System Engineering Department (DISC) and DCAS handled the electrical wiring and the embedded systems. Students in the engineering program, the Master and on work-study programs also took part in the project at various design levels. A critical design review was performed with the experts at ISAE-SUPAERO and ONERA (Office National d’Études et de Recherches Aérospatiales – The French Aerospace Lab).

A thesis dedicated to distributed propulsion to reduce our ecological footprint

This flying demonstrator activity was developed as part of Eric Nguyen Van’s doctoral thesis at the Systems Doctoral School (EDSYS). This thesis is financed by ONERA for 50%. The aim is, first of all, to offer a co-design method to design engine control laws and to determine the size of the vertical tail while meeting flight and safety quality constraints and, secondly, to provide a point of comparison with a solution tested in flight on a demonstrator.

A more precise goal is to look for the best sizing for the vertical stabilizers on aircraft. A smaller vertical empennage consumes less fuel, but it takes more effort to pilot the airplane. In order to provide relief to the pilot, automatic control systems can take over to stabilize the plane, using engine thrust and working with distributed propulsion.

“Instead of designing systems one after the other, we are going to try to optimize the size of the vertical stabilizers and the control systems together by co-designing them, while meeting the constraints laid down by flight and safety quality,” Eric Nguyen pointed out. This process provides a combined result for the study of these two systems, better than the best of each system taken separately.

Distributed electrical propulsion also provides a much better reaction time than a combustion engine or a turbomachine. The use of differential thrust to control the aircraft is another advantage. Using this capacity makes it possible to reduce the surface of the vertical stabilizer and to save on fuel or carry more batteries on a fully electric airplane.

Outlook for the future to meet the environmental challenges of air transport

This flight was the first in a long series that will be used to estimate and study the aero-propulsive interactions that are occur between the propellers/fans and the wing, flight dynamics using propulsion as a means of active aircraft control, and the best positioning for electrical propulsion on an airplane. The study focused on the regional air transport segment, but the methodology can also be applied to any aircraft using distributed electrical propulsion, such as air taxis.

“Eric’s thesis targets a 40- to 70-passenger regional transport propeller airplane with distributed electrical propulsion (Mach 0.5-0.6). This study is a complement to that carried out at ONERA with the design of the all-electric AMPERE general airplane for 6 passengers (500 km at 250 km/h) and of the DRAGON hybrid transport airplane for 100 passengers (1,000 km at Mach 0.7), both with ducted fans,” said Carsten Döll, one of his doctoral advisors who is a researcher at ONERA, co-financer of the thesis.

This research was carried out thanks to the CEDAR Chair – Chair for Eco-Design of AiRcraft – created jointly by Airbus, ISAE-SUPAERO, its Foundation and ONERA. Its purpose is to define disruptive concepts in air transport by including innovative technologies starting in the aircraft design phase to reduce the ecological footprint of innovative technologies. Research efforts will notably focus on dealing with emerging missions in air transport, such as interurban transport covering 200 to 300 km.

More information on CEDAR chair.