Energy efficiency, lower carbon dioxide emissions, smooth operation and better acceleration; the aviation industry is researching hard on making the sky cleaner and greener in the years to come. Newer environment-friendly technologies are emerging to reduce greenhouse gas emissions and use of renewable sources of energy. While aircraft manufacturers are making serious efforts to increase fuel efficiency in existing airplanes with greener engines, experimentation on solar, biofuel and electric aircraft are going hand in hand. The EADS Innovation Works, the research and technology wing of EADS, along with several industry partners such as Aero Composites Saintonge (ACS), Siemens, Roll-Royce, Diamond Aircraft etc is testing a range of electric propulsion systems for aircraft of future generations.. In the quest for more environment-friendly aircraft, the company is exploring a number of possibilities which include a small electric airplane and a hybrid helicopter propulsion system. The EADS ‘E-aircraft’ projects include the electric general aviation training aircraft in cooperation with Aero Composites Saintonge (ACS), called E-Fan and the Diamond Aircraft DA36 E-Star 2, the updated hybrid electric motor glider developed along with Diamond Aircraft and Siemens. The company in collaboration with Rolls-Royce is also working on a smarter future distributed propulsion system concept.

The development of innovative propulsion system concepts for future air vehicle applications is part of EADS’ effort to achieve the aviation industry’s environmental protection goals stated in the European Commission’s ‘Flightpath 2050’ report. The declaration sets the target of reducing aircraft CO2 emissions by 75 per cent, along with reduction of nitrogen oxides (NOx) by 90 per cent and noise levels by 65 percent, compared to standards set in the year 2000.

E-Fan

Designer Didier Esteyne is an engineer and pilot who worked with EADS on the first electric aerobatic plane and the smallest manned aircraft in the world with four electric engines, Cri-Cri, unveiled at the Paris Air Show 2011. The two decided to team up again on E-Fan. Two years later, at this year’s air show at Paris, the teams at EADS IW and Esteyne’s Royan-based Aero Composites Saintonge (ACS) unveiled the E-Fan, a fully-electric general aviation training aircraft.

Co-funded by the Direction Générale de l’Aviation Civile (DGAC, the French civil aviation authority), the European Regional Development Fund (FEDER), the French Government (Fonds FRED), the Région Aquitaine and the Départment Charente-Maritime of France, the two-seat E-Fan is a result of intensive development work undertaken in only eight months. The design process of the aircraft began in late 2011 and the final go-ahead for the technology demonstrator was given only in October 2012. “The introduction of the E-Fan electric aircraft represents another strategic step forward in EADS’ aviation research. We are committed to exploring leadingedge technologies that will yield future benefits for our civil and defence products,” says Jean Botti, the Chief Technical Officer, EADS.

E-Fan features two electrical engines driving shrouded propellers. The total static engine thrust is about 1.5 kN, with the energy being provided by two battery packs located in the wings. The length of the aircraft is 6.7 meters with a wingspan of 9.5 metres. It is the first electric aircraft featuring ducted fans to reduce noise and increased safety. Its main landing gear allows electrical taxiing on the ground without the main engines and in addition provides acceleration during take-off up to a speed of 60 kmph. To guarantee simple handling of the electrically-powered engines and systems, the E-Fan is equipped with an E-FADEC energy management system.

While EADS Innovation Works has developed the electrical and propulsion system, ACS has built the all-composite structure, the mechanical systems and has conducted the aerodynamic studies. The French innovation institutes CRITT Matériaux Poitou-Charentes (CRITT MPC) and ISAE-ENSMA, as well as the company C3 Technologies have been responsible for the construction and production of the wings. Astrium and Eurocopter have helped in testing the battery packs while the livery has been designed by Airbus.

EADS claims that the aircraft has zero carbon dioxide emissions in flight and should bring a significant reduction in noise around airfields. The two-seat E-Fan is suited for short missions such as basic pilot training, glider towing and aerobatics and has a flight endurance of one hour.

E-Thrust

The E-Thrust concept study is part of EADS ongoing hybrid and electrical propulsion system research. Airbus and EADS Innovation Works, along with Rolls-Royce and Siemens are developing a hybrid/electrical distributed propulsion system, as an intermediate but necessary step towards fully-electric propulsion for airliners. With Cranfield University as a partner, the Distributed Electrical Aerospace Propulsion (DEAP) project is co-funded by the Technology Strategy Board (TSB), United Kingdom. The DEAP project researches key innovative technologies that will enable improved fuel economy and reduced gas and noise emissions for future aircraft designs by incorporating a distributed propulsion (DP) system architecture.

Rolls-Royce will develop an optimum electrical system propulsion plant, taking into consideration speed range, maximum speed, number of fan motors, efficiency etc, while EADS Innovation Works will design the electrical system and work with Airbus to optimise the integration of the propulsion system in the airframe.

The hybrid DP architecture offers the possibility of improving overall efficiency by allowing the separate optimisation of the thermal efficiency of the gas power unit (producing electrical power) and the propulsive efficiency of the fans (producing thrust). The hybrid concept makes it possible to downsize the gas power unit and optimise it for cruise. The additional power required for take-off will be provided by the electric energy storage.

The distributed fan propulsion system provides thrust for the aircraft, replacing conventional turbofan engines. The large fan diameter and weight of conventional turbofans limits does not enable advanced aerodynamic efficiency, hence the researchers are experimenting with a number of electrically-driven fans that are integrated into the airframe, allowing for a more aerodynamic overall design. During descent, the energyefficient distributed fans are turned by the airstream and like wind turbines, generate electrical energy which can be stored. “The idea of distributed propulsion offers the possibility to better optimise individual components such as the gas power unit, which produces only electrical power, and the electrically driven fans, which produce thrust. This optimises the overall propulsion system integration,” said Sébastien Remy, Head of EADS Innovation Works.

Tropospheric Airship

EADS Innovation Works is researching on an innovative hybrid airship that is envisioned for use in multi-role missions in Arctic regions, providing a long-endurance platform capable of all-weather operations. Its missions will be environmental and wildlife monitoring, natural resources management, observation and security applications, along with the surveillance of shifting ice patterns and related tracking of ships in the increasing number of open-water routes that are created by the warming climate. The airship is tailored for tropospheric flight up to altitudes of 7,000 metres, with an all-terrain capability allowing its deployment from established base locations as well as unprepared sites without ground support infrastructure.

The Tropospheric Airship which can be deployed on extended surveillance, detection and reporting missions would provide a low-cost new-generation resource that is silent in operation and generates little or no emissions while offering significantly longer endurance than patrol aircraft or unmanned aerial vehicles. The airship’s size will enable it to carry a range of mission payloads.

The Tropospheric Airship is based on an imaginative catamaran-type design combining aerostatic lift with helium gas in a rigid airframe and additional lift from its wings. The variation of the gas volume required for flight up to 5,000 metres is considerably less than the variation needed for 7,000 metres, resulting in a smaller overall hull volume and the possibility to incorporate an innovative buoyancy control system. The Airship has an overall length of 90 metres, width of 60 metres and a height of eight metres. Its novel twin-hull design creates a more streamlined profile than single-body dirigibles reducing aerodynamic drag. The low height, in particular, facilitates hangarage for maintenance, systems integration or storage, thereby eliminating the need for hangars with the extremely high internal clearance required for conventional single-hull airships.

Designed primarily for unmanned missions, the airship is to have an uninterrupted endurance of up to 40 days and the speed will be between 60 kmph and 150 kmph, with this range applicable throughout the airship’s flight envelope. With additional lift being created in forward flight by the fore and aft wings, an altitude of 7,000 metres can be reached. In its secondary role as a cargo transport, the airship can carry one tonne of weight at an altitude of 7,000 metres and seven tonnes at 1,000 metres as external sling loads.

DA36 E-Star 2

At the Paris Air Show, Siemens, EADS and Diamond Aircraft showcased the next-generation DA36 EStar with a serial hybrid-electric drive. This drive concept enables quiet electric take-off and a considerable reduction in both fuel consumption and emissions of up to 25 per cent.

The propeller of the motor glider is electrically driven by a hybrid system, consisting of an integrated drive system from Siemens and a generator that is powered by a small Austro Engine Wankel rotary engine. The DA36 E-Star 2’s drive system provides an output of 80 kW during take-off and a continuous output of 65 kW. The electric motor weighs only 13 kg and at five kW/kg, its specific continuous output is twice that of the first prototype and about five times greater than that of a typical industrial electric motor. The power electronics and gearbox are integrated into the electric motor and included in the weight stated. For take-off and climb, additional energy is drawn from a battery which is recharged during cruise.

EADS and Siemens recently signed a long-term research partnership with Diamond Aircraft. The partnership aims at introduction of hybrid drive systems for both helicopters and large airplanes, while the airworthiness certification of fullelectric and hybrid aircraft in the general aviation category is to be achieved within the next three to five years. The memorandum of understanding between the three companies confirms the collaboration on the project which has existed since 2011.

“Only with innovation we can solve the conundrum of rising fuel costs, rising passenger demand and rising environmental regulations. This makes the research partnership between EADS and Siemens so important,” said Peter Löscher, CEO of Siemens AG. “Innovations used in this hybrid plane will be instrumental in making transportation more sustainable in the long run, whether in the air, on land or at sea.”

“The serial electric propulsion allows us to design airplanes with totally different characteristics than today. Vertical take-off and high-speed cruise can be realised in a much more efficient way. The DA36 E-Star 2 was the next step to prove this technology and through its positive results to continue further developments,” informed Diamond Aircraft owner Christian Dries during the Paris Air Show.