A taxiing problem: inside the FAA’s new IADS software

At present, aircraft movement times on the ground at airports are unpredictable, meaning air traffic managers in the US, the EU, and around the world have to build in bigger buffers, leading to delays on taxiways and runways – and subsequently increased fuel burn and emissions – prior to take-off. 

A research article published by Cambridge University Press looking at the impact of single engine taxiing at London Heathrow found that for a typical landing and take-off (LTO) cycle in the UK, on average 36% of fuel is consumed during the taxi phase. It further estimated that the taxi phase accounts for 12% of nitrous oxide, 89% of carbon monoxide and 91% of hydrocarbon emissions. 

The Royal Aeronautical Society research forecasted that taxi times will increase due to the growing number of air traffic movements and resultant airport congestion; this would therefore increase the contribution of the taxi phase to the LTO cycle and total flight fuel consumption and emissions.

By minimizing taxi delay and ramp congestion, the new IADS software allows the FAA’s Air Traffic Organisation (FAO), airlines, and airport ground operators to calculate the best time for an aircraft to push back from the gate, roll non-stop to the runway, take off as part of a choreographed sequence, and then join high-altitude en-route traffic with greater efficiency and fewer airspace restrictions. 

The software system – part of the FAA’s Terminal Flight Data Manager (TFDM) programme – was developed by NASA and tested for nearly four years by the FAA’s NextGen group, airlines’ airport operations, FAA radar facilities in Charlotte in North Carolina, and Dallas/Fort Worth in Texas, as well as the Atlanta and Washington, D.C. centres tasked with handling high-altitude en route flights.

“When you are ready to go, you want to go. Waiting in line on a taxiway is not part of the flight plan,” says FAA assistant administrator for NextGen Pamela Whitley. “Through a productive partnership between the FAA, NASA and the airlines, we now have technology that brings better predictability of aircraft movements on and above our busiest airports. This will yield benefits for air travellers and for the environment.”

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These benefits, calculated during testing at Charlotte Douglas International Airport, include reduced aircraft taxi times that helped save more than 275,000 gallons of fuel annually, equivalent to the fuel burn of 185 flights between New York and Chicago by a Boeing 737. Environmental gains include a reduction in greenhouse gas emissions of eight tons of CO₂ daily, or almost 3,000 tons each year. 

The software also helped to reduce flight delays, including waiting times of taxiways, by 916 hours, equivalent to shaving 15 minutes of waiting time on a taxiway for more than 3,600 departing flights.

The FAA will roll out the enhanced TFDM, which will incorporate this new push-back capability, at 27 hub airports across the country – beginning in 2022 at Phoenix and Charlotte, and including hubs in Atlanta, Chicago, New York, Washington, San Francisco, and Los Angeles – and could take five to ten years to fully implement.  When completed, the FAA anticipates savings of more than seven million gallons of fuel every year and the elimination of more than 75,000 tons of CO₂ emissions annually.

“NASA is developing transformative technologies that will revolutionize the aviation sector as we know it,” says NASA Administrator Bill Nelson. “The proof is in the pudding. This air traffic scheduling technology enhances aircraft efficiency and improves dependability for passengers every day. 

“I’m excited that the software NASA developed for air traffic controllers and airlines will be soon rolled out at airports across the country and know the results will continue to be extraordinary.”

The FAA’s TFDM programme chimes with President Joe Biden’s plan to release an aviation climate action plan in the next few months. In September, the US government unveiled measures to reduce aviation emissions by 20% by 2030, including a proposed tax credit on fuels that achieve at least a 50% drop in "lifecycle" emissions, as well as $4.3bn in funding aimed at new fuel development. 

The White House said in a statement: “Aviation accounts for 11% of US transportation-related emissions and addressing this pollution source is essential if we hope to put the aviation industry, and the economy, on track to achieve net-zero greenhouse gas emissions by 2050”.

In Europe, taxibots, e-taxi systems, and single-engine taxiing are just some of the technologies under investigation by SESAR JU AEON project, which aims to reduce CO₂ emissions from aircraft taxiing.

Hybrid taxibots are able to tow full aircraft to near the start of the runway, without the aircraft having to start its engines. This is expected to reduce fuel consumption during taxiing by 50–85%. 

An e-taxi, or electric green taxiing system (EGTS), is an autonomous solution that uses electric motors embedded in landing gear to allow planes to push back and taxi without their jet engines running, saving fuel, curbing emissions and ending last-minute delays while waiting for airport tugs. 

This is expected to reduce fuel costs by around 4% of the overall consumption, 50% of taxi fuel and up to 85% of ground operations costs considering other benefits like pushback costs and brake wear.

Single engine taxiing involves using only half the number of engines installed to generate the energy needed for aircraft taxiing. According to the SESAR JU, this can reduce taxi fuel consumption by 20%.

These innovations – along with the new IADS software developed by the FAA and NASA – offer hope that leading edge technology, coupled with ambitious, coherent climate policies from governments, can continue to provide real solutions to the urgent problem of emissions from commercial aviation.

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