The amount of time between aircraft as they land at Toronto Pearson International Airport might seem prosaic to the untrained eye, but there’s a lot more going on than pilots negotiating the gentle return to earth of hundreds of tons of metal.
Every millisecond that passes is tied to a new technology touted as a partial solution to two intractable problems (albeit of wildly divergent importance).
We’re of course talking about airport delays and global warming.
A technology called Intelligent Approach (IA) is constantly working to tighten the space between incoming aircraft as they approach Pearson. It’s one of a number of new systems aimed at chipping away at the carbon footprint of an inherently dirty industry: commercial aviation.
Aircraft that rely on jet fuel aren’t going away anytime soon. While biofuels are slowly growing in use, scaling them to make a major dent in airplane emissions is arguably a long way off. And the battery technology necessary to even consider electric airliners is much more elusive. So commercial aviation says it’s looking to lop off emissions where it can—from the routes aircraft take to the time they spend circling airports, sitting on the tarmac or idling at the gate. All of that time wastes fuel and spews carbon dioxide into the atmosphere.
But while it may seem like any cut in emissions is a good thing, that may not be the case. Critics worry such technologies are a kind of airline greenwashing, inviting consumers to feel less guilty about air travel when they still should. Worse, there are fears these efforts might distract from the real solution.
“For the longest time, aviation as a sector has managed emissions by spreading discourses that, at some point in the future, the issues will be resolved,” says Stefan Gössling, a professor of tourism research at Linnaeus University in Växjö, Sweden. “[But] we have not come any closer to a break in emissions.” Airlines “all know that if they engage with the real issue, which is new fuels, they simply couldn’t afford it.”
Carbon emissions from aviation make up more than 2% of the global total. And because passengers, flights and distances are all increasing, it’s one of the fastest-growing sources of greenhouse gasses. All of this has put more pressure on airlines and airports to decarbonize.
Which brings us back to chipping away at the margins.
IA began as a collaborative effort between airports, air navigation service providers and airlines. When in 2014 researchers showed runway capacity could be increased by using flexible, time-based separations of approaching aircraft as opposed to fixed distances, the idea was born. In 2015, air navigation service provider NATS and technology provider Leidos teamed up to develop the software, first testing it at London Heathrow Airport.
The makers of IA say its mission is to land planes with more frequency and minimize delays, thus reducing fuel burn. It addresses part of a complex aviation puzzle made up of hundreds of operations across arrivals, departures and surface traffic, all of which can cause delays and thus more fuel to be burned.
Since many problems arise when filling an aircraft with fuel, food, luggage and people, or taxiing to and from the runway, there’s always uncertainty in flight schedules; something as simple as a passenger with a dog too big for its carrier can have knock-on effects. While airlines factor this in by adding buffers to flight times, it doesn’t always help: Around 20% of flights are delayed or cancelled each year. The financial impact spreads through the economy as lost time, money and opportunity—for airlines, passengers and companies. But its effect on the environment is worse: backlogs force aircraft to stack up overhead or linger in the taxiways—with their engines on.
“We can ensure that each aircraft lands as close as possible to its arrival time”
For its part, IA’s methodology is pretty straightforward. It takes into account the aircraft type and current weather conditions to calculate the minimum separation between two incoming aircraft. This involves predicting the “compression” that occurs between each pair of aircraft as the lead plane decelerates to its landing speed.
At most airports, the distance between aircraft A, as it makes its final approach, and aircraft B, next in line, is determined by aircraft size. The larger A is, the more turbulence it creates; the larger B is, the more turbulence it can handle. If you have an Airbus A380 with four jet engines followed by a small Beechcraft King Air, the separation needs to be large.
But this fails to account for variables such as wind speed and direction. It doesn’t acknowledge, for instance, that in a headwind the wake behind aircraft A dissipates faster, allowing for a smaller separation. Using radar and aircraft flight data, IA monitors aircraft as they begin their approach. On a calm day, A and B might need to be kept apart by three nautical miles (3.45 statute miles), but in a headwind that can be reduced to around 2.7 nautical miles.
Now in active use at Heathrow, IA enables up to two additional landings per hour in calm conditions and reduces circling time by around 4,784 hours each year, airport officials say. In doing so, it’s saving an estimated 14,442 tons of fuel consumption, or 46,000 tons of CO2.
“If we can deliver close to the same landing rate on a windy day as we can on a calm day, then we can ensure that each aircraft lands as close as possible to its arrival time,” explains Ben Sandford, one of IA’s Product Managers.
There is a dirty irony here. Using IA, airlines and airports can maximize their capacity for a fraction of the cost of building another runway. This means more planes can fly, burning more fuel and adding more greenhouse gases to the atmosphere. Nonetheless, Pearson joined Heathrow as a user of IA this year, and Amsterdam’s Schiphol Airport is to join them in 2023.
At four other airports in Europe, Asia and the Middle East, officials have turned to IntellAct, an Israeli startup that uses CCTV to detect delays caused by cleaning, refueling and restocking of airplanes. Should IntellAct detect any one of these processes is taking too long, it suggests a workaround. If the fuel truck is behind schedule, for instance, IntellAct will recommend refueling take place while boarding passengers.
“A lot of delays can be mitigated with better planning and better communications,” says founder Udi Segall. “If airlines are reacting in real-time, then it’s already too slow.”
But it’s not just private enterprise that’s getting into the act. The Federal Aviation Administration is installing software developed by NASA that coordinates schedules of all airport departures.
When a plane is ready to leave, pilots use its engines to taxi toward the runway. Because jet engines aren’t optimized for ground use, the fuel used on the ground is substantial. During a standard 15-minute taxi, a Boeing 747 can burn more than a ton of it. So rather than have planes line up in a physical queue, NASA’s Airspace Technology Demonstration 2 (ATD-2) software creates a virtual line, such that time normally spent burning fuel on the taxiway is spent at the gate, engines off.
“If airlines are reacting in real-time, then it’s already too slow.”
ATD-2 was first tested at Charlotte-Douglas International Airport in North Carolina. Over four years there, NASA says the software saved almost 6,000 hours of engine-run time, and as much or more than 1 million gallons of fuel. These savings were compounded by a reduction in engine maintenance costs. It also reduced flight delays by 933.6 hours and saved an estimated $4.5 million in value of time.
The system went live at Cleveland Hopkins International Airport last month, with the FAA saying it “will continue activations at dozens more airports in the coming months and years.”
More than 25 airlines have also turned to WheelTug, a device built into the nose-wheel to allow aircraft to push away from the gate without the need for a traditional tug powered by fossil fuels. Not only does it save between six and nine minutes of time per flight, but it can add around two extra flights per gate, according to tests performed at Mumbai International Airport.
But the biggest savings in commercial aviation emissions come from flight. There, too, companies are nibbling around the edges.
Last year, Alaska Airlines signed up with Airspace Intelligence, a Silicon Valley startup whose Flyways platform enables dispatchers to optimize routes between origin and destination. Controllers can use the software to more accurately incorporate weather, traffic volume and airspace constraints into their decisions.
Traditionally, a controller files the proposed route with a regulator around 45 minutes before take off, basing it on what the airspace is like at that particular moment. In some territories, flight paths are tightly prescribed, but in US airspace it’s generally open. The goal is normally to get the flight there as quickly as possible.
What Flyways does is evaluate a trajectory based on what the airspace is going to be like when the aircraft is flying through it. If, for example, a storm is forecast over New York when the aircraft will be there, the platform might avoid it. It will also optimize the route according to the wind direction, saving fuel.
The recommendation also takes into account surrounding air traffic, seeking to ensure not that the flight arrives early, but that it arrives at a time likely to cause the fewest delays in the wider aviation network.
“What is most valuable to an airline is not how fast a flight arrives, but that it arrives in a reliable way,” says Phillip Buckendorf, co-founder of Airspace Intelligence. In 12 months with Flyways, Alaska Airlines says it has saved an average of 2.7 minutes per flight and more than 6,500 tons of CO2 compared to flights not using the technology. That’s the equivalent of more than 17 million miles driven by an average gasoline-powered passenger vehicle.
But Gössling urges caution about relying on these technologies to meaningfully erode aviation’s ballooning environmental impact. They address the least harmful phases of the flight: taxiing, takeoff, approach and landing. At best, he estimates, efficient routing will reduce total emissions by 10%, and eradicating holding patterns will remove around 1%.
Indeed, he says their purported benefits extend no further than local air pollution, because any wider gains are erased by growing passenger numbers, which are forecast to double before 2037. Instead of focusing on reducing the taxi times and separation between incoming flights, the focus should be on minimizing emissions when aircraft are in full flight, Gössling says.
As admirable as they may be in a vacuum, these new platforms will promote a net increase in aviation emissions because they make flying more efficient and attractive, he warns. “We are talking about the most energy intensive form of consumption.” Gössling says. “None of these technologies, even in combination, will cut emissions from aviation to the necessary amount if the sector continues to grow.”
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