The Taxiing Robot Concept

The first vehicle has used a Boeing 747 nose for trials. (Airbus)

Airbus, IAI and TLD explore eco-efficient ‘engines-off’ taxiing. By Tom Allett.

The first vehicle has used a Boeing 747 nose for trials. (Airbus)

At last year’s Paris Air Show Airbus signed a Memorandum of Understanding (MoU) with Israel Aerospace Industries (IAI) to jointly explore and develop application of IAI’s proposed new concept known as TaxiBot (Taxiing Robot).  TaxiBot is a semi-robotic towbar-less tractor (TLT) fitted with hardware and software which enable its use for dispatch towing operations while under the pilot’s control.  The manufacturer says an initial evaluation of this concept has shown promising results.  However, additional studies and tests are ongoing to validate it.
The TaxiBot is designed to remove the need to switch on the aircraft’s main engines during the taxi, although the aircraft’s auxiliary power unit (APU) would need to be activated in order to supply power to cockpit and cabin systems.
Subject to a satisfactory outcome of the assessments that at the time of writing (February) are still ongoing and subsequent operational demonstrations, preparation of a potential joint-venture (or other form of co-operation) could be created to develop a business which would aim to produce and sell TaxiBot tractors to airports and ground handling agents.  This company would be a venture with three main shareholders: IAI, Airbus, and − following an agreement signed at last year’s inter airport Europe show in Munich − French GSE manufacturer TLD.
The MoU with IAI confirmed Airbus’ participation in the feasibility study, in particular regarding aircraft ground tests which are planned to be demonstrated using the Airbus-owned A340-600 dedicated test aircraft.  The MoU assessment phase also covers regulatory, legal/product liability and environmental evaluation, as well as financial viability of TaxiBot.
The aircraft manufacturer’s Executive Vice President, Strategy & Future Programmes, Christian Scherer, said: “Reducing costs and emissions at airports is key to improving our industry’s eco-efficiency.  Airbus and its partner IAI has entered into a promising technical and environmental assessment.  If ultimately successful, such a development would be fully in line with Airbus’ eco-efficiency goals across all aspects of commercial aircraft operations.”
 
The Potential Savings
Obviously, aircraft taxiing at airports burn large amount of fuel, emit tons of CO2, and are noisy.  The aviation industry has long been searching for alternative means to tow airliners from their departure gate to the take-off − or rather the holding point prior to entering the runway − with their engines off, to save the fuel, carbon and noise emissions.  So far, all the attempts to perform dispatch towing (towing fully loaded aircraft with standard tractors) have been unsuccessful from three main reasons.  Firstly, it shortened the aircraft’s nose landing gear’s servicing life cycle, due to the inevitable fatigue effects, and was therefore unwanted by both aircraft manufacturers and airlines alike.  Secondly, it meant that the aircraft would be controlled by the tug driver rather than the pilot during the taxi phase and thirdly, existing TLTs didn’t have enough engine power to tow fully-laden airliners at their usual engines-on taxiing speeds.
The key ingredient in the TaxiBot’s design is that it allows the pilot to retain control of the aircraft during the taxi phase without shortening the nose-gear’s life cycle.  Airbus says the new concept: “addresses all the safety considerations in the towing process, as well as the energy and endurance problems.”
A Command, Control, Communication Centre (C4) system located in the ATC tower and at the towing company’s premises, is there to enable the safe and efficient operation of the TaxiBot fleet while hopefully reducing the probability of runway incursions.
The long-term vision for the TaxiBot system is to implement full airport auto-immunization, improve airport efficiency and increase airport ground movement safety.  Importantly, TaxiBot does not require any modification to the aircraft and only minor adaptations to existing airport infrastructure.
TLD France developed and produced the basic TaxiBot vehicle under a risk-sharing contract.  As this edition went to press the vehicle, fitted with a Boeing 747 cockpit and steerable NLG, was approaching the last few weeks of its initial test phase at privately-owned Dunsfold airfield near London, UK.  Subject to a satisfactory outcome of the initial preparation tests the vehicle will be transferred to Toulouse for a demonstration and evaluation period with Airbus using one of its A340-600s.  This phase is scheduled to finish in April.
A fully operational TaxiBot prototype is planned for delivery by the end of 2011.  The TaxiBot system will have two models to handle both narrow body (NB) and wide body (WB) airliners and when the certification process is complete these vehicles will be able to tow all the main types of commercial aircraft.  At this stage, there is no intension to develop a version for Regional Jets or smaller aircraft.
When I first saw the concept I had wondered how practical it would be at major airports.  I envisaged a queue of airliners all moving towards their departure runway using the TaxiBot system.  If all or even most departures used it, this could create a ‘traffic jam’ of tractors needing to return to the terminal in the face of oncoming aircraft on either the runway or taxiway.
Ran Braier, TaxiBot Programme Director for Israel Aerospace Industries answered: “It is planned that a typical TaxiBot fleet will be able to handle all the mainliner airliner departures at any airport which provides the service.
“There will not be any traffic jams because of TaxiBot operations, since its towing performance in terms of maximum speed, acceleration and deceleration will be similar to those of normal aircraft taxiing on jet power.  On the other hand, there will need to be some adaptation of return or bypass roads − [though] at some large hubs they already exist − that will by used to return the vehicles to the ramp area without driving back on runways or taxiways.”
 
 
 
TaxiBot Aircraft Towing Highlights

  • TaxiBot can dramatically reduce taxiing expenses
  • Reduces air and noise pollution
  • Improves efficiency and ground traffic safety
  • Pilots retain control during taxiing
  • Steers, accelerates, decelerates and stops without NLG damage
  • Minimal infrastructure adaptations are needed at airports
  • No modifications needed to aircraft