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The E-Fan demonstrator crosses the French coast. airbus group
Electric Evolution
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As the Airbus Group E-Fan electric aircraft winged its way across the English Channel recently, one could not help but consider the efforts of Louis Bleriot in 1909. 100 years ago there wasn’t an internet to stream live images across the globe, nor was there a rescue helicopter on hand should Bleriot be forced down over theChannel – such a machine was still decades away from being invented.
The two-seat E-Fan technology demonstrator that flew the English Channel is just the first step.
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However, both flights did share some common threads beyond their French heritage.
They were both confronted with aviation’s ongoing challenge of weight versus power. They also drew attention to their fledgling causes.
For Bleriot in his craft of wood and fabric, it was the birth of aviation.
For the Airbus Group E-Fan, constructed of modern compositematerials, it was the dawn of a new age in propulsion. The electric aeroplane had landed.
The Channel crossing
As with all attention-grabbing flights, a great deal more time is spent in preparation than in execution. The E-Fan had exceeded the flight time and distance requirements in testing well before it crossed the English Channel, but Airbus Group had a good many contingencies to address beforehand.
The key driver behind the E-Fan project and ultimately the Channel crossing was the Airbus Group’s chief technical officer, Jean Botti.
For Botti and his team, safety was the prime concern from the outset and a flight such as this literally called for planning on land, on sea and in the air. Every possible aspect was considered through a series of bench, ground and flight tests before the flight could take place. In the event of a single-engine failure, energy management and a point of no return were calculated.
Even when the E-Fan was proven to be capable to perform the flight, there was still a great deal of coordination required to ensure the safe execution of the crossing.
UK and French authorities needed to be satisfied of the flight’s safe conduct and a corridor of airspace had to be blocked for the transit.
Meteorological services were continually consulted and limiting parameters of wind speed and direction were assigned prior to the flight.
The well-being of the pilot was paramount should the aircraft be forced down over the Channel. As a consequence, a hoist-equipped rescue helicopter was on hand carrying a crewman and doctor with the requirement that the pilot be recovered and in the helicopter within three minutes of a ditching.
With everything in place, the onlyvariable in play was the weather and fortunately clear skies and light winds came to the English Channel on July 10.
More than 100 test flights had taken place before this one significant crossing. These flights resulted in upgrades that significantly improved overall battery and power performance – including the installation of new, more powerful Lithium-ion batteries, as well as a change-out of the electric controllers that convert the batteries’ direct current to the alternating current required by the motors.
Utilising these developments, the E-Fan flew the 74km flight from Lydd in the UK, east to Calais in France, in around 37 minutes, cruising at 3,500ft. In perfect conditions, test pilot Didier Esteyne eased the allelectric aeroplane smoothly onto the runway in front of a waiting crowd and a global audience. It was a far cry from the gusty winds and weather that had challenged Bleriot in 1909, but then again a lot had changed.
An evolution
Cleaner and greener is a constant call in all industries and aviation is no exception. The European Commission’s ‘Flightpath 2050’ environmental protection goals for the air transport industry are to reduce CO2 emissions per passenger kilometre by 75 per cent, NOx emissions by 90 per cent and noise by 65 per cent.
The concept of electric flight is not new and has been pursued through varying routes, such as power generated by solar panels or by batteries. Either way, they are free of fossil fuels and the emissions that are created through traditional aviation powerplants.
The promise of clean, green flight is balanced with a good many technical hurdles between concept and reality, as many have discovered previously. This is something recognised by Dr Detlef Müller-Wiesner, who is responsible for the Airbus Group E-Aircraft Program and something that Airbus is approaching with longterm goals. The two-seat E-Fan technology demonstrator that flew the English Channel is just the first step and is serving as a platform for Airbus Group and its partners to evaluate the new technologies needed for electric and hybrid aircraft.
The E-Fan technology demonstrator has tandem seating, but the E-Fan 2. 0, which will go in serial production, will feature side-by-side seating.
With an airborne endurance of 1. 5 hours this all-electric aircraft will be targeted at basic pilot abinitio training. Airbus Group has sought the input of pilots, flight instructors, flying schools and the French authorities in designing the E-Fan 2. 0 to deliver on their requirements.
The first flight of E-Fan 2. 0 is scheduled to take place in late 2016 and Dr Müller-Wiesner plans for the first aircraft to be delivered by the end of 2017, and there is already interest in the marketplace from private pilots to flight schools. The four-seater E-Fan 4. 0 will be the next step, offering around three hours of endurance and crosscountry navigation capability. It will crack the door on the touring aircraft market in addition to its expanded training capabilities.
Innovations
Beyond the initial electric aircraft concept, the Airbus Group and its partners are embracing innovation in a number of areas. Final assembly of E-Fan 2. 0 will take place at a specially designed 1,500m2 facility in south-western France at Pau Pyrénées Airport at a site that will seek to employ its own new technologies to create a cleaner, more efficient production facility.
Airbus Group is also pioneering the ‘Connected Cockpit’ in the E-Fan. The concept employs one fixed and one removable tablet as the cockpit’s primary displays.
The removable tablet can be pre-programmed in the flight briefing stage in the flight school classroom, allowing both student and instructor to not only discuss the routing, but which cockpit display will be seen at any particular phase of flight.
On board, the tablets provide primary flight displays, engine data and checklists. In flight they provide information relating to the closest airports and the most efficient flightpath to reach them in the case of a low battery situation.
Furthermore, the flight is digitally recorded and automatically stored at the flying school. This allows the Connected Cockpit to provide both an excellent debriefing tool for pilots and a data management system for other tasks such as maintenance scheduling.
Another concept that has longterm development applications is that of hybrid propulsion. Currently being tested in a ground-based platform, a mockup of the hybrid
It would be very easy to forget the immense challenge that electric flight presents.
was on display at Calais when the E-Fan technology demonstrator made its arrival. The hybrid consists of a small piston engine, currently an off-the-shelf 55hp (41kW) glider engine, connected to an electric motor similar to that installed in the E-Fan.
Airbus Group sees the piston engine as a range extender that can both provide energy and recharge the batteries during cruise flight. This system is currently being foreshadowed for employment on the E-Fan 4. 0.
Making it work
With so much positive news stemming from the E-Fan Channel crossing and the new technologies on the horizon, it would be very easy to forget the immense challenge that electric flight presents. In the days of Bleriot, aircraft designers were confronted with the challenge of finding a sufficiently powerful engine without an undue burden of weight. Electric flight has the same hurdle to counter, in addition to others.
The E-Fan has sought to meet the LSA requirement of 600kg, so weight was a major consideration from the outset. The E-Fan battery system comprising of 2,982 cells with a capacity of 2. 8 amperes per hour each is contained within the wing where traditional fuel tanks would be housed. When questioned if solar power could supplement the E-Fan’s needs, Dr Müller-Wiesner explains that employing solar power cells on the upper surface would only offer an extra 2-3 minutes of power per hour and would not justify the increased weight. Accordingly, at this time, the batteries that can be carried offer 90 minutes endurance.
Just as a traditional aircraft is refuelled after flight, E-Fan’s batteries are recharged. A mobilecart that plugs into any industrial-type electrical outlet is used for the recharging process, thereby managing the most efficient power-up cycle.
Furthermore, flight time remaining on an electric aircraft is not as neatly defined as fossil fuel quantity gauges on a traditional aircraft. Battery management, cell group management and thermal factors all affect the reserve of power as it equates to reserve flight time. To manage the demands efficiently, an electrical energy management system known as E-Fadec automatically handles the task, reducing pilot workload.
Battery technology is central to the success of electric and hybrid propulsion. The ability of electrochemical cells to efficiently convert stored chemical energy into electrical energy is paramount.
The advancement of electric cars has been of some benefit to the electric flight cause. Mass production on the ground has led to both a reduction in the unit cost of electrochemical cells and a 60 per cent increase in energy capacity in cell technology over the last year. The upgraded version of the E-Fan technology demonstrator utilises commercially available cells manufactured by Panasonic.
However, while cell availability and cost is ever-improving, the batteries utilising those cells in aircraft is a different matter. The batteries face challenges electrically, mechanically and thermally while seeking to remain lightweight and reliable. Finding a safe and reliable means to connect the cells is a key component in the successful future of electric flight.
Even so, these challenges and the advances the E-Fan has already made hint at something stirring on a much larger drawing board – commercial electric flight.
A Brave New World
The advances in electric propulsion, battery technology and hybrid propulsion are fascinating in their own right. However, beyond the Channel crossing and the ability to train the next generation of pilots in efficient electric aircraft looms the E-Thrust project. A joint project between the Airbus Group and Rolls-Royce, E-Thrust envisages a regional airliner accommodating 70 to 90 passengers.
One key enabler of the project is the advancement of superconductors, materials which have the property of zero electrical resistance when cooled to extremely low temperatures, normally around -245ºC. And the long-term development of an enhanced energy storage capability will also be needed to make this aircraft a reality.
The E-Thrust concept is exciting to behold. Within its sleek futuristic design is a single large gas turbine engine, centrally mounted, producing electrical power which in turn drives six electric engines to provide thrust. Those six engines are in clusters, three on each wing. The aircraft’s heart is a next-generation energy storage system that beats in harmony with the engines through a carefully managed flight profile.
On takeoff and climb the turbine engine powers the six engines to provide thrust, easing back in cruise flight where the energy storage system is recharged. Descent is a managed glide descent with the engines ‘spooling up’ on the approach to land, just as airliners do today but with a far greater degree of efficiency one would imagine.
Could such an aircraft arrive by the European Commission’s Flightpath 2050? If the key enablers of superconductivity and advanced energy storage reach fruition, it is indeed possible and advances are already being made at the E-Aircraft System House in Ottobrunn, Germany. The E-Aircraft System House is initially focusing on the advancement of basic technological expertise and capabilities for individual components, and then investigating their incorporation into sub-systems – such as electric fans and propellers, high voltage platforms, turbines, generators and thermal systems.
Dr Müller-Wiesner foresees that the E-Thrust project will require engines generating between four to five megaWatts each. Already there have been successful ground runs of a hybrid demonstrator in Ottobrunn generating one megaWatt. The future may be closer than we think.
A dream or destiny?
The successful crossing of the English Channel by the Airbus E-Fan echoes a distant past. Just as Bleriot had overcome the challenges of powerplant technology and weight, so too had the E-Fan technology demonstrator with Didier Esteyne at the helm.
And while both flights made their mark, it is the future they foreshadow that ultimately changes the world. For Bleriot it was a century of jet travel and lunar landings that he could not have imagined. For the E-Fan, its new technologies may well be the first small steps towards the next leap forward. This time aviation has a century of advancement already written, so the future does not seem quite so distant.
Is the concept of commercial electric flight a dream or destiny? The truth is that every destiny begins with a dream – just ask Louis Bleriot.
It would be very easy to forget the immense challenge that electric flight presents.
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