Changing the concept of helicopter designs can start only with the evolution of helicopter propulsion and power systems, said a panel at Singapore’s Rotorcraft Asia 2017 conference in April. The panel consisted of Airbus Helicopters chief technical officer Jean-Brice Dumont, Bell Helicopter’s director of innovation Scott Drennan and Pascal Dauriac, Safran's research and technology director.
Dauriac thinks the way forward will follow two development paths; the conventional combustion or hybrid engine design, and the distributed propulsion multi-rotor craft.
However, pure electrical power with today’s battery packs is not sufficient to power even a multi-rotor aircraft carrying two passengers for 20 minutes, and he foresees only hybrid propulsion system consisting of combustion and battery to be feasible within the next decade. He believes that as proof-of-concept; a prototype can be developed with a central engine connected to the various electrical generator and motors.
“This [multi-rotor] system is the answer to safer missions thanks to redundancy to the many rotors and will venture into new missions and markets,” Dauriac said. “It might not be the most energy-efficient solution at the moment due to the numerous transfers from fuel; to electrical; and to mechanical energy.”
“The overall architecture of the plane and helicopter hasn’t changed. But distributed propulsion, if we get there, will be a game changer with new shape and design. But right now, we are stuck,“ said Airbus's Dumont. “Propulsion development has been steady, but hasn’t seen any exponential growth.“
Meanwhile, Safran’s Arrano engines are now achieving 10- to 15 percent reduction in fuel burn and C02 emissions, and the French company hopes to achieve 25 percent by 2025 on a 2,500- to 3,000-shp engine with electrical assistance. Beyond that, they hope to develop a Constant Volume Combustion (CVC) engine with 35 percent lower fuel burn and emissions. Dauriac said the CVC is very complicated to develop and factors such as noise, leakage and pressure have to be considered. He estimates it won’t be ready until 2030.
Airbus Helicopters is developing the Clean Sky 2 (CS2) high-speed rotorcraft in line with the European Clean Sky initiative to reduce carbon emissions over Europe. Co-funded by the European Union, the CS2 hybrid helicopter is based on the company's X3 concept demonstrator, which includes two tractor propellers on short-span wings. Currently 37 partners from 12 countries are on board the CS2 program.
The concept aircraft is to cover more ground at 1.5 times the speed of most helicopters, which could be extremely useful in Emergency Medical Services and Search and Rescue Operations. CS2 is projected to consume 15 percent less fuel per nautical mile at 180 knots compared to a standard helicopter at 130 knots. Airbus hopes to start assembling the first demonstrator prototype by December 2018, and have the platform airborne by 2020.
Bell Helicopter likewise has big ambitions for its FCX-001 concept rotorcraft unveiled this year at the HAI Heli-Expo. It aims to introduce new advanced anti-torque technology and alternative propulsion. The FCX-001 will have no tail rotor and is said to use thrust-vectoring for anti-torque control.
Drennan says the priority for Bell's innovation department has always been high speed VTOL development. Short-term plans include projects such as the V-280 Valor tiltrotor which aims to make its flight debut this year.
Autonomous flight is increasingly within reach, and both airframers are taking steps to reach that goal. The City Airbus project is part of the company’s ambition to achieve urban air mobility. The development of a quadcopter is underway, and Dumont hopes that the platform will fly soon, first with a pilot, followed by unmanned operations. “It will also be our first large-scale distributed propulsion. We might not be the first to do so, but we want to be ready for the market down the road,” he said. “It is not just about the development of the aircraft, but also the infrastructure, regulations and air traffic management.”
While Bell does not have any high-profile autonomous program lined up, the company's breakthrough project is its Model 525 Relentless; the world’s first fully fly-by-wire helicopter. Drennan said that is one of the first steps to autonomous flights.
“As a community we have to be ready for the breakthrough, and when it comes, it will change us,” said Airbus’s Dumont, in closing.