Airbus announced earlier this month that it has developed an eco-efficient alternative to using jet engine thrust for ground taxiing operations, which is highly inefficient as the engines run but the aircraft does not move very far. Aircraft spend a high proportion of overall flight time on the ground taxiing, with engines running at idle and below optimal conditions, Airbus says. Indeed, for short haul flights of 60-90 minutes, up to a third of third of total trip time may be spent on the ground.
The new system relies on electrically-driven wheels rather than the engines to move the aircraft. The Airbus-developed solution is simple: an electric actuator, powered by the aircraft's auxiliary power unit (APU), drives the landing gear’s wheels. As the APU runs on kerosene, fuel consumption is expected to be five times less than it would be with engine power – saving as much as 200 kilograms of fuel per flight.
In addition, this alternative delivers a feature much requested by airlines: the aircraft can reverse back from the boarding gate by itself, as no tug is required.
“Autonomous taxiing and tug-free push-back are hugely attractive to aircraft operators, giving Airbus a competitive advantage,” said Airbus research and technology engineer Jérémy Bedarrides, who took part in the system’s development. “With the deployment window we have and the patents we hold, we are ready to support Airbus' leadership in innovation.”
Apart from fuel-saving benefits, the new technology will result in quieter airport operations and fewer ground vehicles. As an airliner would be independent of ground manoeuvring vehicles, turnaround times would be faster and operations would be cheaper.
Design and implementation for the project, involving Airbus’ Engineering and Procurement department, is progressing in two concurrent stages. The demonstration phase is scheduled to close in 2012 with completion of the prototype electric wheel actuator. In parallel, the modified APU and power systems will be tested on the Airbus electrical test bench, with full-scale rolling tests to begin in 2013. If all goes as planned, initial flight tests will take place the following year.
In theory it would be possible to spin up the wheels before landing using this system, thus extending tyre life dramatically because the stationary tyres would not initially slide and smoke on the runway at the point of touchdown. Airliner tyres are changed after between a hundred and several thousands landings, according to maintainers and pilots.
Similarly, in May last year Delos Aerospace announced it holds two patents for a system for reducing aircraft fuel burn through the use of in-wheel electric motors/generators. As an aircraft landed, it would use the electrical generators to brake, as conventional, heat-inducing brakes would be discarded. The regenerative braking system would convert the breaking motion into electricity, which would be stored and used when the aircraft manoeuvres on the ground. The benefits include reduced engine wear, faster breaking and longer tyre life if the tyres are spun up before landing.