![The APU will provide electrical power to drive the taxi motor through gearing assemblies on the inside of one main landing gear wheel. [Courtesy: Green Taxi Solutions]](https://flyingmag1.b-cdn.net/wp-content/uploads/sites/2/2025/09/FLY0925_3.5-Jumpseat-1.jpeg?width=1250&height=720)
The majority of musings in this column involve experiences and airline-relatable topics. Not often are specific aviation products discussed.
But when Green Taxi Solutions appeared on the radar, it was hard to resist a system that has the potential to be a game changer. When the installations begin, airline pilots will have to adjust not only their aircraft operation but their mindset.
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The system is designed to taxi the airplane without use of engine power. The APU will electrically employ a motor connected to one wheel hub of the main gear. A control box, ergonomically located most likely in the center pedestal of the cockpit, will be operated by a pilot. Steering and braking will be controlled in the same manner as is currently performed via a tiller, rudder pedals, and toe brakes. The normal control box functions are only for speed, forward and reverse. More details shortly.
Green Taxi Solutions CEO David Valaer started his fledgling pilot career as a floatplane fish spotter in Alaska flying a Super Cub. At the age of 23, a near midair that involved an up close and personal encounter with another fish spotter’s Cessna 180 that filled his windscreen with a tire presented him with an epiphany: Maybe this wasn’t an appropriate career path. A landing on the ocean in rolling seas after experiencing a smoke-filled cockpit also assisted in redirecting his career aspirations.
Valaer still wanted to remain a pilot, so he joined the Iowa Air National Guard. He had the rare opportunity to be one of the last in flying the A-7 Corsair, taking it to the boneyard after six months of duty. He transitioned to the F-16 and thought his career might be finished after ingesting a wayward buzzard through the engine while flying low level over the Florida Everglades. Fortunately, Valaer managed to limp the airplane back to MacDill Air Force Base in Tampa. He completed eight years of service.
Setting aside his flying experience, Valaer has a very respectable résumé, inclusive of educational degrees and tons of experience in the aerospace industry. At 32, he bought Simplex Aerospace, a helicopter firefighting systems manufacturer, which was sold to Dart Aerospace. Before selling the company he was the sole owner and CEO, involved with FAA certification, engineering, sales, customer support, and quality control, among other functions.
A chance meeting with Joe Hoffman at EAA AirVenture in 2019 led Valaer on the electric taxi path and the founding of Green Taxi Solutions in 2021. Hoffman held the intellectual property rights for a similar system when he had worked for L3 Technologies, which had demonstrated it on an A-320 in 2011.
The concept of a no-engine taxi is not new. In 2005, Boeing Phantom Works in partnership with Chorus Motors demonstrated the WheelTug—a prototype system on the nosewheel of a B-767. In a joint venture between Safran and Honeywell corporations, their prototype Electric Green Taxiing System was presented using the main landing gear of an A-320 at the 2013 Paris Air Show. Unfortunately, or fortunately, depending on what side of the equation you are on, these systems either floundered or never reached full supplemental type certificate(STC) status because the cost of jet fuel had plummeted. The airlines had moved on to other cost priorities.
Fast-forward to the present day, and the Green Taxi Solutions (GTS) system becomes more relevant. As a matter of fact, the FAA endorsed the concept by awarding the company and its partner, StandardAero, a $5.6 million grant based on the initiative of the Continuous Lower Energy, Emissions, and Noise (CLEEN) program.
European aviation is ahead of the U.S. in its environmental impact initiatives. As an example, Amsterdam Airport Schiphol (EHAM) is pushing for a zero-engine taxi by 2030. Taxi bots are being developed for just that purpose. Heathrow Airport (EGLL) in London is actively planning for similar reductions in environmental impact.
GTS estimates 126,000 gallons of fuel saved or approximately $306,000 annually per aircraft. Carbon emissions reduction, less brake wear, less noise, and less turnaround time are additional advantages. Pushback costs are drastically reduced. Engine maintenance is reduced. The risk of foreign object damage (FOD) is reduced. The safety risk for ground personnel is reduced. The number of tugs required for pushback is reduced.
So, how does the system work? As mentioned earlier, depending on the aircraft, a control panel will be installed in a location for ease of pilot access. The control panel consists of a simple on/off switch, a forward/reverse switch, an emergency stop switch, and a light that indicates the normal or abnormal temperature of the taxi motor. Pilots will steer via the airplane tiller or rudder pedals as before. Braking is the same.
The APU will provide the electrical power to drive the taxi motor through gearing assemblies on the inside of one main landing gear wheel. Although nosewheel installation was considered because of an easier assembly process, it was determined that slippage or lack of torque in a low friction environment, like snow and rain, or a taxi on an uphill grade, would be better served by power from the main landing gear.
But what if the system faults? The drive pinion gear is designed to be physically disconnected via the following methods: system off position disengages the motor because of a mechanical spring; control panel on/off switch; exceedance of the maximum ground speed of 25 knots occurs; weight-on-wheels (WOW) sensor disengages if liftoff occurs; system fault; full electrical failure; a separate system will hydraulically disconnect the motor via the emergency switch on the control panel; a shear pin breaks if excessive loads are placed on the main wheel.
As for training pilots on the system, Valaer does not believe airline simulators will require modification but rather some type of cockpit procedure trainer will be utilized. Considering that moving the airplane backward is contrary to most airline pilot’s psyche—except for those of us that performed pushbacks with reverse thrust 100 years ago—it will be a learning curve. Ground crews will also need procedural training because the system isn’t designed with cameras, so they will have to be the eyes of the pilots.
The goal of GTS is for certification in 2027. The Embraer E-175 is the targeted airplane with Delta Air Lines, Alaska Airlines, and SkyWest Airlines indicating their willingness to begin installations. The B-737 and A-320 are most likely next in line. Because of the higher cycles with regional jets and narrow body fleets, widebody airplanes that fly one or two legs a day won’t be a priority for GTS. Installation for the retrofit is estimated at two days, with scheduling planned during major maintenance checks.
WheelTug is still in the game, but Valaer doesn’t consider it competition from the standpoint that its system is intended primarily for the ramp area and not for an entire taxi cycle.
The no-engine taxi concept is indeed an innovative design. It will be interesting to see if airline pilots embrace the technology. The fail-safe engineering will certainly assist in promoting confidence with the system.
This column first appeared in the September Issue 962 of the FLYING print edition.
