Taxiing times

Amsterdam’s Schiphol Airport is making constructive use of its current downtime to test hybrid tow-tractor technology, it tells Tom Allett

Airports everywhere are dealing with an unexpectedly quiet time due to COVID-19, but Amsterdam Schiphol Airport is taking the opportunity to begin hosting sustainable aircraft taxi trials using TaxiBot tow-tractors. Long-time readers of Airports International will recognise the TaxiBot name, it having featured in the magazine on numerous occasions since development began around a decade ago.

KLM Royal Dutch Airlines is just one of the partners in the TaxiBot trial. The airline expects the hybrid vehicle to reduce fuel consumption during taxiing by 50%-85%
KLM

However, some readers may not have seen one in action, so be prepared for a surprise as they work in a very different way to traditional aircraft tow-tractors.

The TaxiBot gets its name from being semi-robotic. It was developed through a partnership between Israel Aerospace Industries (IAI), the French GSE manufacturer, TLD and Airbus. It is different from other gate-to-runway towing vehicles because of a mechanism that connects the tug to the aircraft that allows both tractor and airliner to be manoeuvred by the pilots from their cockpit while the aircraft’s engines are shut down. It is intended to save fuel that would otherwise be burned when the aircraft taxies 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 once the pushback is complete, the vehicle is controlled by the aircraft’s pilot, steering it via 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 as it approaches the end of the runway, after which the tractor is driven back to the terminal while the aircraft departs. Another unique element is the tractor’s crab-steering mechanism that keeps it in line with the fuselage of the aircraft it is towing, regardless of any turns.

Amsterdam Schiphol is conducting its TaxiBot trials in collaboration with its air traffic control provider, the Netherlands Ministry of Infrastructure and the Environment, as well as Corendon Dutch Airlines, KLM, Transavia and easyJet
Schiphol Group

The TaxiBot vehicle being tested at Amsterdam Schiphol belongs to Smart Airport Systems, a sister company of TLD, and is one of only ten in the world. It is powered by a hybrid combination of electric and diesel engines which, according to the manufacturer, consumes 95% less fuel when taxiing than the aircraft engines would normally use.

Schiphol is conducting its trials in co-operation with its air traffic control provider, the Netherlands Ministry of Infrastructure and the Environment, as well as Corendon Dutch Airlines, KLM, Transavia and easyJet. Aircraft handling is provided by dnata and KLM Ground Services.

"With a KLM departure to Runway 36L, the runway with the longest taxi times, we maximised the potential fuel savings"Schiphol Airport

The trials, which are expected to run until the end of June, began by towing an empty Corendon Boeing 737 to several runways and ultimately progressed on to ‘live’ operational aircraft.

Schiphol expects to achieve a total savings of 50-85% on fuel consumption during taxiing as aircraft will still burn some fuel while their engines warm up for a few minutes before departure. Measurements are being taken during the testing phase to see what fuel savings and emission reductions can be made. On average, departing aircraft take 14 minutes to taxi, whereas arriving aircraft take around nine minutes.

At the time of writing, Willemeike Koster from the airport’s press office said: “We have tested and validated both TaxiBoting procedures and uncoupling points at the airport, as, by the nature of TaxiBoting, these uncoupling points are at locations which are new for both pilots, TaxiBot operators, and air traffic control.

“We have also performed the first live missions, including the departures of Corendon Dutch Airlines and KLM flights. With a KLM departure to Runway 36L, the runway with the longest taxi times, we maximised the potential fuel savings.”

Schiphol added that the TaxiBot trial is part of a wider feasibility study into sustainable taxiing at the airport. This will include how this process can be integrated into daily operations, whether it is achievable on a large scale and how long the transition phase will need to be and when it will take place. A post-trial consideration of the TaxiBot is expected to be complete this autumn.