E-Fan “Plus:” Opening a new era in electric flight

The demonstrator aircraft will help Airbus validate hybrid propulsion technologies

Following its starring role at this week’s EAA AirVenture Oshkosh fly-in convention, Airbus’ E-Fan “Plus” demonstrator will be readied for its new role as a hybrid testbed combining the energy of lithium ion batteries with a flight range-extending thermal (internal combustion) engine.

Airbus debuted E-Fan “Plus” at EAA AirVenture Oshkosh

E-Fan “Plus” has been a center of attention at the annual U.S. event, held at Wisconsin’s Wittman Regional Airport, which attracted an estimated 563,000 attendees during the seven-day gathering that wraps up today.

“The Airbus team really appreciated the interest from American visitors; many thanked us for what we have accomplished and encouraged us to continue pursuing more-electric aircraft, which they believe is vital for the future of aviation,” explained Mathieu Aubert, the E-Fan “Plus” program manager at Airbus Innovations – the Airbus’s corporate-level global research and technology network that is managing the E-Fan project.  

Debuting the “Plus” configuration

It was a fantastic experience being at Oshkosh and being able to discuss the E-Fan ‘Plus’ project with an audience that is truly passionate about aviation

Mathieu AubertE-Fan “Plus” Program Manager, Airbus Innovations

EAA AirVenture Oshkosh marked the debut of E-Fan in its new “Plus” configuration, building on flight experience gained as an all-electric aircraft version, including the history-making English Channel crossing in July 2015

After the post-Oshkosh shipment of E-Fan “Plus’” back to France, activity will focus initially on aircraft performance with its conversion to the hybrid demonstrator, which involved integration of the range extender engine and an associated electrical generator to provide electricity for recharging the lithium ion batteries while in-flight. 

Modifications for the “Plus” version include two upper fuselage air intakes for cooling of the range extender (REX) system – consisting of a thermal engine manufactured by German manufacturer SOLO Aircraft Engines, along with the electrical generator and related power electronics. Air intakes for the REX installation are mounted on removable panels for easy access to the range extender, while exhaust/ventilation outlets are located on each side of the aircraft.   

The all-electric arrangement for E-Fan’s English Channel crossing last year used a total of 2,982 Panasonic lithium-ion battery cells (18650 size, rated at 2.8 amp-hours), which have been replaced in the E-Fan “Plus” configuration by 1,128 more powerful lithium-ion batteries from LG (in the same 18650 format).  The batteries are located in the forward wing root areas on both sides of the aircraft.

Upcoming flight testing

After its U.S. debut, E-Fan “Plus” will be used to validate hybrid propulsion technologies

While the total weight of batteries has been reduced from the E-Fan definition to offset the range extender system’s installation on E-Fan “Plus,” the new LG lithium-ion cells require more temperature control, resulting in additional air intakes incorporated on the inboard wing leading edges and the installation of small upper-wing outlets that contribute to passive air cooling.

Aubert said an important aspect of the E-Fan “Plus” upcoming flight testing – supplemented by additional ground-based evaluations using the program’s hybrid system test bench – will be how to manage safe and automatic shifts within the aircraft’s various power modes.

“Switching from the aircraft’s batteries to the range extender – and transitioning safely between the two – is actually very complex, with the potential for strong currents through the system,” he added.  “We want to reach the point where such changes can be managed at a flip of the switch; pilots shouldn’t have to worry about what’s going on behind them.”

Prior to its appearance at EAA Oshkosh AirVenture, the E-Fan “Plus” logged more than two hours aloft in seven flight tests, according to Didier Esteyne, the E-Fan designer and test pilot.  These flights were performed from the aircraft’s French home base in Medis, near Royan in the Charente-Maritime region, where the aircraft was built for Airbus Innovations by Aero Composites Saintonge.

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