Farnborough Air Show

E-Fan Advances The Case For Electrically Powered Aircraft

 - July 15, 2014, 6:30 AM
Airbus and its partners hope to see the first light trainer versions of its electrically powered E-Fan aircraft enter service at the end of 2017.

The Airbus-led effort to develop viable electrically powered aircraft was boosted by the first public flight of the first E-Fan aircraft on April 25. The first of the two- and four-seat E-Fan light training aircraft are due to enter service by the end of 2017, but the wider success of the program–which eventually hopes to prove the case for electrically powered regional airliners–is contingent on its developers achieving further technology breakthroughs in harnessing the new power source.

See video The Future of Airliners Is Electric.

With a group of partner companies from France’s Aquitaine region, Airbus, Daher Socata and Aero Composites Saintonge (ACS) have committed almost $68 million to develop the initial E-Fan 2.0 and 4.0 models. The consortium plans to build a 16,146-sq-ft (1,500 sq m) factory for the new family at Mérignac near Bordeaux, and it hopes to achieve full production by the fall of 2017.

The first E-Fan flight involved a 15-minute sortie by a two-seat 2.0 model. “It flies just like a piston-powered aircraft, except that you have to constantly manage the [electrical] power consumption,” explained test pilot Didier Esteyne. He has been closely involved with ACS in the development of the first prototype. The certification program for the new aircraft will involve around 50 flight test hours.

In the first instance, Airbus’s goal is to enter the market for light training aircraft to be used for preparing ab initio pilots. “There will be around 650,000 new pilots undergoing training in the next 20 years,” predicted Jean Botti, the Airbus Group’s director of technology and innovation.

The European airframer aims to win around 10 percent of the market for flying-school fleets, which it believes will account for at least 21,000 new aircraft over the next two decades. According to Airbus’s E-Fan program director, Emmanuel Joubert, the Mérignac factory will be capable of an annual production rate of between 50 and 80 aircraft. The facility is also serving as a testbed for advanced production techniques such as automatic riveting and augmented reality to ensure that the finished product reflects every detail of the digital design.

The main responsibility for taking the E-Fan 2.0 and 4.0 into production rests with Daher-Socata, with the partners eager to capitalize on its experience in producing the TB20 piston single. Stéphane Mayer, CEO of Daher’s aerospace and defense division, said that between 15 and 20 of his employees will be working on this project over the next three years.

But there are some fundamental technology issues that will still have to be resolved if electrically powered aircraft are to have viable, wider applications. While electrically powered engines are far quieter and around 20 to 30 percent less expensive than conventional aircraft powerplant, their batteries are very heavy. The batteries for the four-seat E-Fan 4.0 weigh 286 pounds (130 kg). Roughly speaking, it takes a battery weighing around 30 kg (66 pounds) to generate power equivalent to that produced from just 1 kg (2.2 pounds) of conventional jet fuel.

On the other hand, the power yield from electric motors is far more efficient than that of conventional aircraft engines. With an electric motor about 90 percent of watts generated are usable for propulsion. For typical piston engines, this ratio falls to around 20 to 25 percent.

“We are going to work on making the batteries lighter and more efficient, mainly with Saft [the battery specialist],” said Botti. For example, there are plans to replace the current Lithium-ion batteries on the E-Fan aircraft with Lithium-air or sodium batteries. The partners also are working on improving the Fadec engine control for the aircraft’s electrical propulsion unit.