With technological developments promising changes in the way the aviation industry operates, we could well see a future where aircraft will be able to move autonomously on the ground – all with the help of an innovative concept that only uses the auxiliary power unit (APU).
Explaining the product in basic terms, Jan Vana, the director of WheelTug, said that its innovation helps the aircraft move forward and backward autonomously, eliminating the need for a tug.
“It is a special motor that is embedded in the nosewheel of the aircraft, and it is powered by the APU,” Vana told AeroTime during an interview at the World Aviation Festival 2023. “WheelTug is operating within the […] electric taxi [market].”
According to the Czech executive, the pilots operate the device by pushing a button on a small panel in the cockpit, allowing them to turn the aircraft at the gate as well.
“There are also a couple of lights that indicate the status of the system and that is it,” Vana said, wrapping up a complex concept in simple terms.
“There are multiple benefits for the airlines and airports,” Vana added.
One of these benefits is that by eliminating the need for a tug, airlines save a lot of time while the aircraft is on the ground. Vana highlighted that not only do pilots sometimes have to wait for a tug to be available, but the process of connecting and disconnecting the tug can take up valuable time.
And while every minute saved has a different value for different types of airlines, Vana noted that this was especially the case “for low-cost carriers, which fly short sectors,” since less time spent on the ground means more time in the air.
“We can save a lot of time,” Vana added.
Vana said that with the help of WheelTug, which will allow aircraft to move across the ramp aided by the APU and without using the engines, passengers will be able to disembark from both exits as the innovation eliminates “the risk of a jet blast […] from the gate area”.
The obvious benefit, of course, is the fuel savings.
Airlines have been using a single engine to taxi-in or taxi-out at airports. The International Federation of Air Line Pilots’ Associations (IFALPA) highlighted its position on engine-out taxi (EOT) stating that “one or two engines shut down can help to reduce noise, emissions and fuel use during taxi-in and taxi-out”.
With WheelTug, only the APU would be used to conduct these procedures on the ground. Subsequently, this makes airport operations more environmentally friendly by reducing exhaust and noise emissions, something that has also become a pressing concern for communities living near airports.
“More and more airlines are doing single-engine taxi operations, but some still do not do it,” Vana explained.
As a result, the value proposition differs for individual cases, but the conclusion can be made that less time spent in the air can equate to more revenue-generating opportunities for airlines.
Vana also noted that maintenance costs are reduced by using the WheelTug, and pointed out that engines do not ingest small foreign object debris (FOD) like sand and/or dust, which “happens in some environments”.
However, airlines have not rushed to commit to the product. Vana said that while over 25 airlines signed up to equip more than 2,500 aircraft with the WheelTug, the signatures were placed on Letters of Intent (LoI) “as it is customary in the airline industry for technology that is not yet certified”.
“We are in the final phase of the certification with the [United States (US) Federal Aviation Administration (FAA) – ed. note],” Vana continued, adding that certification from other civil aviation administrations, like the European Union Aviation Safety Agency (EASA), will come from the FAA’s respective bilateral agreements.
The executive noted that certification is being carried out in the US because the company’s assembly line is based in Baltimore, Maryland.
“Once we certify with the FAA, we expect that other authorities will follow with their approval shortly after,” Vana said.
According to Vana, the final phase of certification can mean a timeline of anywhere between 15 and 24 months, meaning that the FAA could grant certification in 2025.
Throughout the certification process, the FAA’s main concern, as always, has been safety.
“We did the safety analysis and told the FAA how we address the potential safety risks,” Vana said, adding that the WheelTug is a “very low safety risk system”.
Furthermore, the regulator will be certifying the WheelTug as exempt from the master minimum equipment list (MMEL). This means that if the autonomous tug does not work, the aircraft can still operate and fly.
“One of the main safety risks was to answer what would happen if the pilot forgot to turn off the system,” Vana said, noting that additional risks were the activation of the system in the air and whether or not the WheelTug is susceptible to being an elevated fire risk.
Vana noted that these issues were “just some of the things that you need to answer during the certification process”.
Another issue that remains is the question of how the landing gear and the wheel itself handle the increased weight from adding the WheelTug. However, Vana said there are established processes to assess this issue, including steering and other tests.
The certification process will conclude once the FAA issues a Supplemental Type Certificate (STC), which will affirm that the system is safe and ready to be used by airlines.
“Pilots will receive computer-based training to use the WheelTug,” Vana said.
Airlines will also have the option to add cameras to the WheelTug system, so that pilots are able to see the underbelly and, subsequently, what is behind the aircraft.
“Like a parking system on the car,” Vana explained.
Fully autonomous future
The WheelTug executive envisions a future beyond the usage of the taxi system, noting that the company’s goal is to enable completely autonomous ground operations at airports.
However, the concept behind the WheelTug is not original. There is a patent that goes as far back as 1907 that envisioned a similar system.
“The idea is not our invention,” Vana noted. “Our invention is this high-torque motor that makes it happen.”
The idea looks simple on paper, with Vana comparing it to a car using its reverse gear to go backwards, leading many to question why aircraft cannot already do that.
WheelTug is not the only company to offer an option for aircraft to autonomously taxi. However, what makes this product unique is that it is an onboard system and airlines can retrofit their fleets to include the WheelTug system on their aircraft.
The company’s work will not end with the FAA granting an STC.
“Long-term future for me, the very long-term future, means a fully automated airside where aircraft can maneuver autonomously while being monitored by the pilot,” Vana revealed.
Being powered by Artificial Intelligence (AI), such systems would eliminate or minimize the need for traditional ground handling equipment and, by extension, prevent incidents such as ground collisions between two aircraft.
“This is how I think airside operations will look in the future,” Vana said. “Maybe not in the 2030s, but maybe in the 2050s.”