An Electric Green Taxiing System (EGTS) is an electric taxiing system which allows aircraft to taxi and pushback without requiring the use of aircraft engines, and is designed to reduce fuel volumes used by aircraft and reduce greenhouse gas emissions during ground operations. EGTS technology enables aircraft to avoid using their main engines during taxiing and instead taxi autonomously under their own electrical power, using the Auxiliary Power Unit (APU) generator. The system is designed for single-aisle aircraft, such as the Airbus A320 and the Boeing 737.
EGTS is an electric taxiing system that is used prior to takeoff and can help airlines reduce costs by eliminating the need to use jet engines which are not efficient on the ground. It can also reduce foreign object damage and is environmentally friendly as it reduces carbon and other emissions created during the taxiing phase. The main landing gear is equipped with an electric motor powered by the auxiliary power unit which allows the aircraft to push back from the gate and taxi without a tug or its jet engines.
With electric motors located on each of the main landing gear driving inboard wheels and powered by the APU generator, the EGTS system allows aircraft to push back from the gate without a tug tractor and taxi without the use of the main engines.
The Pilot Interface Unit enables the pilot to switch on the EGTS and select the desired taxi speed (forward) or push back speed (backwards). The EGTS controller receives and converts the pilot's directives into orders to power the electronics.
The wheel actuator applies the required torque and speed proportional to the wheel as per the instructions received from the Wheel Actuator Controller Unit (WACU). The WACU converts current into instructions to the electrical motor proportional to the pilot's command as delivered by the EGTS controller.
A patent for electric taxiing was applied for by Delos Aerospace in 2003, and published in 2006.
Honeywell and SAFRAN announced their joint venture EGTS International at the Paris Air Show in 2011.
Following the initial phase of ground testing and first move in April 2013, the system was first demonstrated at the Paris Air Show 2013.
In March 2014, Honeywell and Safran signed a Memorandum of Understanding with GoAir to support the advancement of the EGTS taxiing system. GoAir will test the system and supply operational data to have an accurate projection of fuel saving to potential customers.
At Farnborough Air Show in July 2016, while the development was successful and customers were interested, Honeywell terminated its joint venture with Safran with low oil prices sapping its market but Safran will continue to work on taxiing systems as system design was completed while its A320 demonstrator had been decommissioned since 2013.
Competitor Taxibot is the only certified and operational alternative taxiing system in the market; it is a semi robotic tractor which meets the aircraft for taxi-in and taxi-out, once connected it is controlled by the pilot. Competing products in development by WheelTug are different as they are installed on the nose gear.
In 2011, L-3 Communications trialled a similar main landing gear electric taxiing system on an A320 non-flyable demonstrator with Lufthansa Technik and others, and proposed to develop the eTaxi system with Crane Aerospace but abandoned its plans in 2013 due to high investment costs. Another competitor is WheelTug, whose patent describes it as a drive motor inside the nose wheels. Wheeltug hopes to enter service in 2018 when it hopes to obtain initial certification on the Boeing 737.
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