The Taxibot demonstration vehicle in its final assembly (photo: IAI)
Mon 6 July 2009 – Israel Aerospace Industries (IAI) and Airbus have agreed to jointly develop and test an innovative environmentally-friendly, towbar-less tractor fitted with hardware and software that will enable pilots of both wide and narrow body aircraft to taxi to and from the gate without the use of their jet engines. An initial evaluation of the concept, called Taxibot, has shown promising results, says Airbus, and will now undergo further ground tests in Toulouse. The aircraft manufacturer says that taxiing at airports using main engines is forecast to cost airlines around $7 billion by 2012 and results in emissions of around 18 million tonnes of CO2 per year.
The crucial difference between standard tow tractors and the Taxibot is that its semi-robotic system allows the pilot full control of the system during the taxiing process and uses the existing airplane controls in the same way that the pilot is accustomed to when taxiing using the airplane’s engines. Its use requires no modification to the airplane, so could be used by all aircraft types, and minimal modifications to the airport infrastructure that will not affect existing taxiways and runways, says IAI. Although the Taxibot eliminates the need to turn on the main engines during taxi, the aircraft’s auxiliary power unit (APU) would still need to be activated in order to supply power to the cockpit and cabin systems.
IAI estimates that the Taxibot concept has the potential to reduce the 18 million tonnes of CO2 emissions to less than 2 million per year, along with significant reductions in airport noise levels.
The testing will take place during the remainder of the year on an Airbus-owned A340-600 widebody aircraft. The assessment phase will also cover regulatory, legal/product liability and environmental evaluation, as well as the financial viability of Taxibot.
Subject to a satisfactory outcome and subsequent operational demonstrations, the two aerospace manufacturers will approach an aircraft tractor manufacturer to develop a business which would aim to produce and sell Taxibot tractors to airports. IAI claims first deliveries could take place by the third quarter of 2011.
“Reducing costs and emissions at airports is key to improving our industry’s eco-efficiency. Airbus and its partner IAI will now enter into a promising technical and environmental assessment,” commented Christian Scherer, Executive Vice President, Strategy and Future Programmes. “If ultimately successful, such a development would be fully in line with Airbus’ eco-efficiency goals across all aspects of commercial aircraft operations.”
The concept of towing aircraft to and from runways with their engines off to save fuel and emissions has been under consideration by the industry for some years. Virgin Atlantic carried out test trials in December 2006 at London’s Heathrow and Gatwick airports in which aircraft were towed by electric tugs to holding areas consisting of several parking bays – so-called ‘starting-grids’ – close to a runway before take-off. Once on the grid, the aircraft would start its engines around 10 minutes before actual take-off. Virgin Atlantic held talks with three international airports in the US about holding similar trials. However, no more has been heard from the airline on the outcome.
WheelTug, based in Gibraltar, has developed an aircraft drive system that enables later-generation Boeing 737 aircraft to back away from gates without using a tow tug, and to taxi to and from runways without running their engines. The system is designed around twin high-torque motors integrated with the aircraft’s two nosewheels. It uses electricity generated by the aircraft’s APU, which produces the electric power to run WheelTug as well as the aircraft’s other electrical systems.
The company estimates that compared to a conventional dual-engined taxi, ground emissions of CO2 by a Boeing 737NG can be reduced by over 650kg for a typical flight, based on fuel savings of 200kgs, or more than 65%. WheelTug has recently produced data to show significant reductions in other pollutants such as carbon monoxide, nitrogen oxides and hydrocarbons.
Delta Air Lines became a development partner in 2007 and is the launch customer for the WheelTug system.
The system will first be marketed as a retrofit solution on the 737NG, with the company aiming to offer it later as a retrofit on a range of other narrowbody aircraft and business jets.
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