In less than two decades, Airbus’s concept for the VoltAir E-Fan could spawn a new family of 100-seat regional airliners with a hybrid-electric propulsion system anchored by diesel engines sending 6MW of power to a row of electric thrusters.
The potential 100-seat aircraft is still early in the design phase, but Airbus already appears to be leaning toward a familiar configuration.
“We’re starting to work on the design of what we call the EPU,” says Ken McKenzie, deputy chairman and senior vice-president of strategy and corporate services for US-based Airbus Group Inc. “We’re actually preferring a hybrid engine.”
McKenzie links the Airbus design to the NASA N3-X concept that emerged about five years ago, revealing a blended-wing body with gas turbine engines generating electricity for a row of electric thrusters buried in the boundary layer flow along the trailing edge of the fuselage.
“That’s a similar idea,” he says. “It may not be a gas turbine in our case. It may be diesel.”
A particular concern that arose about the N3-X was the amount of shielding required to protect passengers from the spillage produced by the semiconductors, which would transfer the power generated by the engine to the thrusters. McKenzie says that issue will have to be addressed in the Airbus design as well.
Airbus has previously discussed the hybrid-electric 100-seater as a 10-year goal, but McKenzie sets that timetable back by almost a decade further.
“I think more realistically it’s a 2032 time window for a commercially viable aircraft,” he says.
The concept leverages Airbus’s plans to introduce an electrically-powered, two-seat trainer in 2017 called the E-Fan 2.0 and a four-seat, hybrid-electric 4.0 model afterward. The company on 10 July flew an E-Fan demonstrator 40nm (74km) across the English Channel to showcase its electric propulsion concept.
The hybrid-electric system for the E-Fan 4.0 is expected to provide critical information for Airbus engineers working on the 100-seater. The propulsion for the four-seater will have an unusual configuration, with a single engine driving two electric fans, McKenzie says. If the concept resembles the propulsion configuration for the 100-seater, it raises intriguing questions, such as how Airbus would compensate for excess yaw if one of the fans stops working.
“You have one motor, but you have two thrust-producing devices,” he says. “The asymmetric thrust has to be almost zero, so if you lose one it can still fly on the other. One of the concepts we had was if you lose one the other one stops too.”