Tractors For Tomorrow

Can we envisage the day when a fully automated tow tractor – perhaps electrically powered – can deliver the world’s largest airliners from parking stand to hangar? (KEY– Tony Dixon)

Will we see fully automated aircraft tow-tractors developed or do the risks outweigh the benefits?  Tom Allett reports.

Can we envisage the day when a fully automated tow tractor – perhaps electrically powered – can deliver the world’s largest airliners from parking stand to hangar? (KEY– Tony Dixon)

In June I was one of a group of journalists taken to visit the Siemens Airport Centre near Nuremberg in Germany.  The two-day visit was an opportunity for the company to showcase its wide range of airport products that provide a vision of how airports will look in the future.  A presentation called ‘The Efficient and Green Airport’, by Siemens’ Director of Portfolio and Innovations, Franz-Josef Herchenbach, touched on the idea of automated tow-tractors that would manoeuvre airliners from their parking stand to the end of the runway without the need for a driver.
Having been in the commercial aviation industry since the early 1980s, I have seen a few changes that would have been impossible to conceive when I started out.  However, despite the fact that automation has brought the biggest changes of all to this industry, I still struggled to imagine an airport where towing manoeuvres will be fully automated.
 
Remote Control
While not truly automated, there are already semi-remote control tractors commercially available.  Schopf’s PowerPush, for example, allows a single staff member to drive the towbarless tractor up to – and lock itself around – the tyres of the main landing gear of aircraft such as the Boeing 737 / Airbus A320 families.  The driver then simply steps out of the cab, moves away from the aircraft to give him/her a better view of the manoeuvring area and, with the aircraft brakes off, performs a pushback by using a remote control device.  The PowerPush uses hydraulically-driven spinning ‘arms’ that turn the aircraft’s main wheels, thereby moving it as required.  However, true automation would go one step further, completely eliminating the need for a driver.  Control could likely be via a single – perhaps office rather than ramp based – operator that would handle and monitor several such movements at a time.
Initially I thought a completely automated tow-tractor driving up to, attaching itself and then towing a very expensive airliner to another parking stand, or maybe the maintenance hangar on the opposite side of the airfield, was strictly science fiction.  However, perhaps it isn’t impossible after all.  The French tow-tractor manufacturer TLD is already promoting an automated version of its TaxiBot vehicle that is currently being developed in conjunction with its Israeli partner IAI.  The initial TaxiBot design needs a driver to position the vehicle onto the aircraft’s nose gear, but from then on, the tug’s movements – and those of the aeroplane attached to it – are controlled from the aircraft’s flight deck.  It is intended that this type of vehicle will be used to manoeuvre airliners from their parking gate to the end of the runway, thereby saving the fuel that would otherwise be burnt by the aircraft’s engines during the taxiing phase.  Only their Auxiliary Power Units need be engaged in order to provide electrical power to the aircraft.
Jean-Marie Fulconis, President & CEO of ALVEST and the TLD Group told Airports International: “We have worked in the past on installing a remote control system on our small electric towbarless tractor, just for pushback applications.  It required a person walking beside it and remotely commanding the movement of the tractor.  This project is do-able with no problem, but we did not complete it because our initially interested customer changed its mind.
“Regarding other projects, we are cooperating with IAI on the TaxiBot project and we already well engaged in the design phase.  But, as of today, there will be a driver in this tractor, although the pilot will be in command for most of the towing operation.  The driver will make the push back, and then take command to disconnect the tractor from the AC and return to the terminal.”
Three months of tests in co-operation with Airbus, using a TLD towbarless tractor attached to the nose gear of an A340-600, ended on June 4.  Initial versions have been described as ‘steer-by-wire’ with separate vehicles being developed to handle either narrow or wide-bodied aircraft, and the pilots on board the aircraft will be responsible for direction, speed and braking.  This product is thought to be approximately two years away from being commercially available, but Airbus has already stated that a fully automated version – supervised by pilots – is also “under consideration.”
Another manufacturer that worked in cooperation with Airbus is Sweden’s Kalmar Motor.  The company’s Magnus Johansson told Airports International: “It depends on what phase of the towing operation you want to look at, but overall I believe that the benefits of having fully automated tractors are low.  In terms of automation, we have developed a system whereby a tractor towing an airliner out to the holding point for departure at the end of the runway can have its speed fixed automatically by the air traffic controllers.   For example, if ATC determines that the tractor and aircraft need to move forward at 5km/h in order to fit into the flow of departing traffic, then they are able to set this speed and even if the tractor driver applies more power, the tractor won’t exceed the 5km/h limit, but for safety reasons the tractor still needs a driver.  Full automation may be technically possible, but I still think the potential benefits are too low to make it worthwhile.  It might work at 5km/h, but not at 20 or 30km/h because of the safety issues.  If you have something stop in front of you then the risk of collision is too high.  I don’t think you are even reducing your staff costs as you will still need people at the departure gate to supervise the operation.”
 
Next Step
While automated tractors are obviously many years from being introduced at airports, a somewhat similar type of vehicle is already in use at the port of Fisherman’s Island in Brisbane, Australia.  There, totally automated vehicles known as straddle carriers have been moving freight containers from ship to truck loading points since 2002.  Their job starts at the point where the crane offloads the container from the ship and ends when they are lifted onto a truck (or vice-versa).  The automated container delivery vehicles are controlled – perhaps a more accurate description would be programmed – by a single staff member.  Then, using millimetre-wave radar as the vehicle’s primary navigation sensor to pinpoint its starting point and a collision-warning sensor to avoid obstructions, the vehicles manoeuvre, position themselves, lift, carry and deposit the containers to the required location without further human intervention.  While this would seem to prove that the technology to perform an aircraft tow already exists, it must be noted that these vehicles operate within a ‘sterile’ environment which has no other potential vehicle or ‘wandering’ human hazards to impede their journeys.  Is such a sterile environment possible on an airport?  It is difficult to imagine and of the average freight container is far more robust than an airliner’s fuselage – and isn’t filled with passengers and fuel.
Among Siemens’ views on airports of the future is this vision of automated tow tractors that manoeuvre airliners without the need for a driver. (Siemens)

Certainly, the necessarily very accurate GPS-maps that will provide a automated vehicle with precise and reliable location information are already available but, because there are so many different ground services that need access to an aircraft during the turnaround, in a situation where a guaranteed sterile area is needed, perhaps the activity around one parked aircraft would potentially delay an automated push/tow taking place from the stand adjacent to it.  At present the push would simply be marshalled by ground staff to ensure that potential collisions are avoided, but if radar-guided vehicles are used, perhaps the potentially highly ‘stop-start’ nature of such a manoeuvre would be counter productive.  Generally speaking, replacing manpower with automation is an obvious money saver, but only if an equivalent level of efficiency is maintained.
Mike Doane, Sales Director for Douglas Equipment Ltd, says he is very interested in automated aircraft tow tractors, adding: “We did look at this a couple of years ago for a specific project using towbarless tractors and certainly the technology is available, but at that time the potential customer and the industry was not ready to consider such a concept.
“If this is to be considered again it would still have to be based on the towbarless tractor concept (to eliminate towbars and the danger of aircraft / tractor separations) and it would have to be an airport wide project as a significant investment would be necessary in airport infrastructure, control systems and safety systems.
“Several possible systems immediately spring to mind: either a guided wire system, a tag (spot) guidance system or a radar guidance system.  We were considering the radar guidance system as it offers much greater flexibility and a simpler installation that can easily be reconfigured.”
Goldhofer’s Marketing Manager, Erich Traub, commented that Towbarless towing without an operator is not an option offered by the German manufacturer at the moment because the company thinks: “there are too many problems to ensure the necessary safety.”
Australian tug builder Bliss Fox has a similar company view with Bryn Jones saying: “This [idea] is very futuristic.  I’ve got to admit that we are not doing any research at this stage into autonomous tractors.  We were invited by Airbus two years ago to participate in its Alternative Taxiing Means – Engines Stopped project, but declined on the basis that we had committed to many other R+D projects on at that time.
“I think the aviation sector can learn a lot from the mining industry where there have been important advances in automation over the last ten years or so. Tracking and control of driverless equipment that comes into contact with very expensive aircraft will be a big challenge.”
David Avery at Navtech Radar has been working, usually in conjunction with universities, on radar-guided systems for outdoor industrial automated guided vehicle applications for more than 20 years.  He told Airports International that he believes that radar rather than wire-guided vehicles had the most potential.
“We can already automatically manoeuvre a tow tractor using existing technology such as millimetre-wave radar and obstacle detectors.
“We are quite disappointed that we haven’t received more contracts for automated vehicles,” says Mr Avery, pointing out that elsewhere, the technology is much more in demand.  The US Department of Defense, for example, is already aiming to completely automate 60% of its vehicles operating in the battle area, but of course that is driven by the desire to save lives in the most dangerous of situations imaginable, rather than saving money in an already highly safety-conscious industry like aviation.
“Nevertheless,” says Mr Avery: “to produce a totally automated aircraft tow-tractor would still need considerable investment – and only the big companies have the ability to do this – but it can be achieved.  Control tolerances need to be looked at in detail, but given that you use very precise mapping, you will do the job better than a human being can.”
Of course the global economic downturn means that investing in development is currently more difficult than it once was.  For manufacturers, deciding whether to spend on development in order to try to leap ahead of competitors or hold back and risk them doing the same, is more difficult than ever.  However, given that everyone needs to continue moving forward to a certain extent, I asked Mr Avery what he thought had prevented an automated tow tractor from being available already; was it purely the cost of investment?
“No,” he replied: “it’s the fear of litigation.  The potential cost of litigation in the event of an accident causes most fears, and until the industry can come to terms with the situation, it will continue to be a problem.”