U.S. startup Green Taxi Solutions has partnered with aftermarket services provider StandardAero to certify its electric taxiing system, initially on the Embraer E175, with funding support from the FAA.

Backed by a $5.6 million grant from the FAA, StandardAero will lead the supplemental type certification (STC) effort, aiming for approval on the E175 by early 2027. Embraer is supporting the effort with data, says David Valaer, Green Taxi founder and president.

Founded in 2021, Arizona-based Green Taxi acquired the intellectual property for the electric taxiing technology demonstrated on an Airbus A320 in 2011 by a team led by L-3. The startup pivoted to target the A220 but is now focusing on the Embraer regional jet.

“The E175 was recommended to us by the industry because they saw that there were more airframes in use, with quicker turn times,” says Valaer, noting that Delta Connection, which operates more than 200 E175s, averages 4.56 flights per day per aircraft.

Green Taxiʼs Zero Engine Taxi system is powered by the aircraftʼs auxiliary power unit (APU). While the E175 has less APU power, 60 kVA versus 90 kVA on the A220, relative to the aircraftʼs weight the Embraer regional jet has a higher APU power-to-weight ratio. “That gives us more performance,” he says.

In a major change, the startup is going back to driving the main gear for electric taxiing on the smaller E175. L-3ʼs original A320 demonstration used mainwheel drive, but Green Taxi planned to power the nosewheel on the A220.

“We looked closely at the nosewheel and after analyzing the space available, and the downward load available we migrated to the main gear,” says Valaer, adding the decision is supported by Embraer. The goal is to have the electric motor drive on one mainwheel only.

“If we can keep it to one wheel assembly, it simplifies and lightens the system. The system weight will be at or below 300 lb., which is dramatically lighter than the previous … system,” he says, referring to the eTaxi system under development by Safran Landing Systems.

“It takes about 3,000 gal. of fuel over a year to carry that 300 lb., which is basically a passenger and a half, versus the 80,000 gal. fuel saved [by electric taxiing]. So, less than 5% of the savings are used for the cost to carry the system on the aircraft all of the time.”

Taxiing by powering only one mainwheel raises the question of side loads on the nose gear, but Valaer notes the E175 is certified to taxi on one engine, “which is significantly more thrust than you would have from the one tire.”

StandardAero is putting together a compliance checklist with the FAA for the STC. “Then we will know specifically the regulations we have to comply with,” he says. “By the end of 2025, the compliance checklist will be done, and the preliminary design will be done.”

The goal is to build a conforming prototype for development and certification testing in 2026. “That way we can do a DER-viewed [FAA designated engineering representative] installation conformity. Our hope is that would occur in the 2026 time frame,” he says.

Electric taxiing was first demonstrated by Boeing in 2005, but despite the long delay in bringing the technology to fruition, “the market is probably the best it has ever been,” says Valaer, citing the confluence of three forces: net-zero pressures, fuel prices and the industrial base.

“Amsterdam Schiphol Airport has legislation in place that would prohibit taxi operations with jet engines. Many people are doing single-engine taxi—weʼve trademarked the name Zero Engine Taxi,” he says, adding the issue is not just emissions of CO but of particulate matter and local air quality at the airport.

Schiphol has used the TaxiBot automated tug, but Valaer says the challenge is twofold: “Who owns it and how do you get it back through the queue of aircraft? Thereʼs a lot of operational concerns with a tug-type solution. Weʼre really the only one with certified solution that will take the aircraft to the end of the runway.”

Green Taxi is targeting a maximum taxi speed of 16 kt and sufficient acceleration so the system can be used with the standard operating procedure for single-engine taxiing. In addition to fuel savings, there will be reductions in tug delays, brake wear and foreign object damage to engines.

Green Taxi plans to lease the system to customers and is promising a 50% rate of return on dollars spent. “Our economic analysis is itʼs approximately $300,000 per year in savings. Letʼs say itʼs half that, our lease rate will be something where theyʼll have a 50% return on investment, and thatʼs just the direct cost—the pushback, the brakes and the fuel,” he says. That does not include any savings from reductions in engine damage and carbon taxes or improvements in ground personnel safety.

In addition to helping Green Taxi obtain certification, StandardAero will use its FAA parts manufacturer approval (PMA) to provide quality control for the manufacture of Zero Engine Taxi kits. “We will own the STC, but under license they will do the PMA of our parts and conform them to the type design before they go out to the customer,” says Valaer.

After the E175, Green Taxi plans to expand its STC to all models in the Embraer regional jet family, including the E170, E190 and E195 and the second-generation E2 series. The startup has had preliminary discussions with Airbus about equipping the A320 and A321. “That would be the next aircraft,” he says. “I could see us doing that in the next year or two.”