New E-Fan Plus updates mark progress on Airbus’ roadmap toward more electric airplanes with reduced emissions and quieter flight
In converting E-Fan to its new “Plus” hybrid configuration, Airbus has made changes to this demonstrator aircraft that go more than skin deep.
The most visible modifications for E-Fan Plus are the installation of a thermal (internal combustion) engine as a flight range extender, along with the accompanying addition of two upper fuselage-mounted air intakes for its cooling airflow, and exhaust/ventilation outlets on each side of the aircraft.
By integrating this two-stroke thermal engine from German manufacturer SOLO Aircraft Engines, the flight time for E-Fan Plus will more than double – increasing to approximately 2 hours and 15 minutes, compared to one hour when making its historic all-electric crossing of the English Channel in July 2015.
A transformation for E-Fan
Less evident, but equally important, is the significant transformation of the electrical system aboard E-Fan Plus, performed under the guidance of Airbus Innovations – the Airbus’s corporate-level global research and technology network.
The aircraft’s voltage was increased from 270 V to a new level of 400 V, providing better electrical performance in powering E-Fan’s two electric propulsion motors, according to Denis Chapuis, who heads the Global Innovation Network for Electronics and Sensors in Airbus’s Corporate Technical Office.
Accompanying the step-up in voltage was a redesign of E-Fan’s electrical architecture and the adaption of its power controllers. Additionally, a purpose-designed command and control computer was added to safely manage the aircraft’s transition within its different operating modes, using the power of its batteries and/or employing the thermal engine as a range extender.
Updating E-Fan: a walkaround
Wing leading edge
The E-Fan aircraft demonstrator’s evolution to the hybrid E-Fan “Plus” is highlighted in this photo series at EAA OshKosh AirVenture with Didier Esteyne, the E-Fan designer and test pilot. Here, he points to the additional air intakes incorporated inboard on the wing leading edges as part of the passive cooling system for the new LG lithium-ion batteries.
Two upper fuselage air intakes on E-Fan “Plus” provide ventilation for range extender system (REX). The REX inlets are mounted on removable panels to facilitate access to the range extender’s internal combustion engine, and the associated the related power electronics.
Range extender system
With one of the access panels removed, the range extender system’s two-stroke thermal engine is visible behind the pilot seat. This two-stroke, water-cooled engine is from German manufacturer SOLO Aircraft Engines.
Changes on E-Fan “Plus” include exhaust/ventilation outlets installed on each side of the airframe for the range extender system (REX) and the electrical generator with its related power electronics. They are located under the aircraft’s shrouded propulsion engines and are covered by a fairing.
Didier Esteyne points to the upper-fuselage fairing that covers the fuel cap to E-Fan “Plus’” 51-liter tank. The tank is filled with widely-available aviation fuel (avgas) for the thermal engine that serves as a range-extender (REX).
Higher power with new batteries
Another modification was the change-out of Panasonic lithium-ion batteries that equipped E-Fan for its English Channel crossing, replaced by lithium-ion batteries from LG that are 15 percent more powerful.
E-Fan’s total battery weight of 168 kg. for the English Channel flight was reduced to 63 kg. in the “Plus” configuration to compensate for the thermal engine system’s installed weight, and a passive cooling system was introduced to provide better temperature management for the higher-intensity batteries.
“Start small, solve small”
Valuable experience also was gained on electromagnetic interference (EMI) and electromagnetic compatibility (EMC) issues for electric propulsion systems aboard aircraft such as E-Fan, that are built with a significant percentage of composites – the materials of choice for new-generation airplanes.
“Evolving E-Fan to its Plus configuration presented a very complex integration challenge that yielded many ‘lessons learned’ at the system level, representing an essential step forward in Airbus’s electric aircraft roadmap,” Chapuis concluded. “Even if we are working with comparatively low power levels on E-Fan today, the transition to its hybrid arrangement is providing us with valuable experience for the future by using the ‘start small, solve small’ approach.”
In their own words
Using the ‘start small, solve small’ approach, we’re gaining valuable experience in complex challenges for the next generations of e-aircraft