Trialling the Taxibot

Tom Allett visited Châteauroux Airport in France to witness the start of a TaxiBot demonstration.

TaxiBot, a hybrid diesel-electric, towbarless tow-tractor aimed at delivering a quantum leap in fuel economy has undergone a week-long trial at Châteauroux Airport in central France.
The semi-robotic tow-tractor has been under development for almost three years by the Israel Aerospace Industries (IAI), TLD and Airbus partnership.
It stands out from other manufacturer’s gate-to-runway towing vehicles because a mechanism that connects the tug to the aircraft allows tractor and airliner to be manoeuvred by the pilots from their cockpit while the aircraft’s engines are shutdown.  It is designed to deliver huge fuel savings that would otherwise be burned when the aircraft taxied under its own power.
The TaxiBot tow-tractor still has a driver who sits in its cab for the pushback phase and for safety reasons but, after the pusback is complete, the vehicle is then controlled by the aircraft’s pilot, steering by the same tiller used during normal – engines on – taxiing manoeuvres.  Braking actions use the aircraft’s brakes, rather than the tow-tractor’s, thereby reducing the stresses normally placed on the airframe’s nose gear.
The airliner’s engines are only switched on at a suitable stage, such as a taxiway holding point, when the aircraft nears the end of the runway, and the tractor is driven back to the terminal while the aircraft departs.
Another unique element to the tractor is its crab-steering mechanism that keeps it in line with the fuselage of the aircraft it is towing, regardless of any turns.
The development of narrow and widebody-capable TaxiBot vehicles is already at an advanced stage.  A widebody demonstrator vehicle completed initial trials at Frankfurt Main Airport in December 2010, successfully manoeuvring a Lufthansa Boeing 747-400 in snow and ice while temperatures dropped to as low as -17oC.  Readers who attended inter airport Europe at Munich in October 2011 may have seen the narrowbody/single aisle TaxiBot prototype on display.  It won the Innovation Award for the interRamp category at the show.
Following the Munich event, the TaxiBot prototype for single-aisle aircraft went back to the TLD factory for harness modifications and new hardware integration.
The first autonomous roll-out took place at TLD’s Montlouis-sur-Loire factory in February 2012; at the same time as a critical design review (CDR) of the widebody vehicle took place.  All the TaxiBot partners participated in the CDR: main partners Airbus and IAI, risk-sharing subcontractors TLD and Siemens, and IAI’s engineering subcontractor Ricador.
Statistics on savings
The TaxiBot joint venture companies have calculated estimated achievable cost savings, based on an oil price of $2.98 per gallon in 2020 and a study of industry statistics.  They believe that a combination of annual fuel savings made from the pushback and taxiing fuel costs of the world’s airliner fleets, plus a reduction in accidental Foreign Object Damage-related (FOD) incidents – the majority of which take place during the taxiing phase – can reduce airline costs by a staggering US$8.7 billion.  In addition, it is estimated the taxiing emissions of the world’s airliners will be reduced by about 23 million tons of CO2 per year if the TaxiBot method is widely adopted.
Boeing airliners do not need any modifications to use the TaxiBot but, on existing Airbus airframes, due to their fly-by-wire systems, a single cable must be added in the nose bay area to connect tractor and airliner.  This modification enables the aircraft’s computer data to be read.  Ran Braier, IAI’s TaxiBot Programme Director, told Airports International: “It’s a very simple modification and no extra weight is carried by the aircraft.  From now on all new Airbus aircraft are being delivered with the cable modification already installed.”
In April 2012, the narrowbody prototype, designed to handle Airbus A318 to A321; Boeing 737 to 757 and MD80 to MD90 airliners, was shipped to Châteauroux Airport in central France to start its test programme.  A retired ex-British Airways Airbus A320, leased by IAI, is being used for the trials.  After successful solo driving tests the first nose landing gear clamping took place on April 19 and, after completion of IAI’s Vectronic Software integration, the first dispatch towing took place.

Test pilot Hen Raz, of IAI, manoeuvres the TaxiBot and Airbus A320 by using the same steering tiller that guides an aircraft during its normal engines-on taxiing. (KEY – Tom Allett)

Week-long trial

On November 19, 2012, a week-long demonstration of the TaxiBot’s capabilities to potential customers began at Châteauroux.  About 20 journalists were taken on board the Airbus A320 while it was manoeuvred around the airport’s runway and taxiway layout by IAI test pilot Hen Raz.  The TaxiBot’s speed control is similar to that of an automatic car.  It starts to move on release of the handbrake.  After TaxiBot has accelerated to the maximum speed allowed for the type of taxiway it is travelling on the pilot uses the aircraft’s pedal brakes, as required, to stay in the desired position amid other traffic.  Several 270o turns were completed during the demonstration of approximately 30 minutes and the ride was every bit as smooth as a passenger could expect in a taxiing aircraft.  Over the next four days, pilots and other representatives from several airlines experienced the tractor’s capabilities.
Costs and questions
Deliveries on the narrowbody tractors are scheduled to begin in the second quarter of 2014, while widebody versions look set to be available from the end of that year.  IAI and TLD estimate unit costs of about US$1.5 million for a narrowbody vehicle and US$3m for its more powerful sibling.  The mathematics to determine a customer’s return on investment will be interesting because while tow-tractor purchase costs will be met by ground handling providers, the fuel savings produced will be made by the airlines.  It raises the question of how ground handling companies will charge their customers for having a TaxiBot-assisted departure, and presumably, because of the relatively high initial purchase price, the handling agents will need to charge an airline more for TaxiBot-aided departures.  It remains to be seen if an airline wants to save ‘x’ amount of fuel on departure whether it will need to pay a premium handling charge.
Another question to ponder is the route the tractor will need to take as it returns to the terminal after release from the aircraft.  The closer the TaxiBot can deliver the aircraft to its departure point, the more money it will save the airline, so the availability of tractor routes back to the terminal will have to be considered at every potential customer’s operating airport.  Nevertheless, TaxiBot appears to be the only way of reducing fuel consumption and emissions by the end of 2013 so it is unquestionably a ‘green’ option for the industry.