Aerospace manufacturers look to electricity for developing aircraft ground taxiing green technology
DLR test engineer in front of the electric nose wheel (photo: DLR)
Mon 11 July 2011 – Current analysis shows that the world’s short-haul aircraft burn around five million tons of fuel annually during ground taxi operations, along with the damage to the environment and wear on aircraft brakes and equipment. Some airlines have experimented with having their aircraft towed to the runway, many others with single-engine operations as they make their way to and from the apron. Now, two projects have been launched that will develop technology to avoid the need for aircraft engine-powered taxiing and instead use electric power. Together with its research partner the German Aerospace Center (DLR), Airbus is examining the potential of fuel cell technology to supply power. Aerospace manufacturers Honeywell and Safran, on the other hand, are to look at how an aircraft’s Auxiliary Power Unit (APU) could power electrical motors in its main wheels.
In 2008, Airbus and DLR successfully performed a flight test on a civil transport aircraft where a fuel cell system provided power for the aircraft’s back-up systems. A DLR-designed technology demonstrator has now been installed in the DLR Advanced Technology Research Aircraft (ATRA) A320 fuel cell test aircraft in Hamburg. The technology demonstrator consists of a fuel cell powering an electric motor which drives the nose landing gear wheels, allowing the aircraft to taxi autonomously.
Testing is taking place to validate the understanding and potential of fuel cell technology for powering future aircraft functionalities such as autonomous taxiing, says Airbus. While DLR will be driving some of the basic research activities for aerospace fuel cell technology, Airbus is in charge of the overall aircraft system architecture and technology integration into the aircraft. The landing gear itself, together with the integrated DLR-designed fuel cell powered motor, has been provided by Lufthansa Technik.
The fuel cell system installed on the ATRA for the tests delivers enough electrical power to move the 47-ton aircraft across the apron. To accomplish this, the fuel cell system powers two electric motors that are built into the rims of the aircraft nose wheel. As a direct electrochemical energy converter that generates electricity from hydrogen and oxygen, the fuel cell operates with significantly greater efficiency than an internal combustion engine coupled with a generator.
“The potential saving at Frankfurt Airport from the use of electrically-driven nose wheels for Airbus A320 class aircraft is about 44 tons of kerosene per day,” says Thorsten Mulhouse from the DLR Institute of Flight Guidance.
During the recent Paris Air Show, Honeywell and French aerospace giant Safran signed a MoU to create a joint venture that intends to deliver an innovative electric green taxiing system for new and existing aircraft. The companies expect it to be installed on new aircraft and retro-fitted on existing planes from 2016.
The partnership will bring to together Honeywell’s auxiliary power experience and Safran’s landing gear know-how. Both companies will contribute expertise in electric power, mechanical systems and systems integration.
They expect to leverage an aircraft’s APU generator to power electrical motors in its main wheels without using main engines during ground operations. Unique power electronics and system controllers should allow the pilot to control the speed, brakes and direction of the aircraft throughout ground transportation.
The companies say the new system could save customers up to 4% in total fuel consumption and emissions. As ground taxiing is a greater percentage of total aircraft use for short-haul operations, with a higher impact on profit margins, Honeywell and Safran say they intend to focus efforts on narrowbody aircraft, which are more likely to be used for short-range flights.
Aircraft equipped with the system will also be able to ‘pushback and go’ more quickly, thus reducing gate and tarmac congestion, improving on-time departure performance and saving valuable time on the ground, claim the companies.