Frequently Asked Questions (FAQ)


What aircraft platforms are targeted for the GTS (Green Taxi System)?

The GTS system is capable of being installed on any aircraft or helicopter that has an APU (Auxiliary Power Unit) installed. The system has been demonstrated at various airshows on the Airbus A320 narrow body aircraft.

Are the aircraft original equipment manufacturers involved with the project?

Airbus has provided a No Technical Objection (NTO) for the GTS on the Airbus A320 and Boeing has agreed for GTS to use their extensive system patent.

How long is the development cycle?

Development of the FAA conforming prototype system is expected to take about 12-24 months from customer launch.

How long to get certified?

After prototype completion, approximately 12-24 months is required to complete FAA Supplemental Type Certificate (STC) certification. Therefore, the total development time for development and certification from receipt of order is 24 to 48 months.

What is the certification plans for the system in multiple other countries?

The system will also be designed to EASA (European Authority for Aviation Safety) standards and the EASA approval based upon the US FAA STC approval.
GTS will work closely with the regulatory authorities in other countries to achieve operational approval of the system based upon customer’s requirements.

With all the system benefits, why is it not in use already?

The original system was developed and prototyped by the team of Honeywell, L3 and Safran. Due to falling fuel prices in 2015, competitive complications within the companies, final system production was not achieved. Many interested parties were very disappointed in the outcome and have encouraged GTS to continue towards production. The current team consists of former Honeywell and L3 team members who were/are committed to seeing the industry changing system come to completion.


What is the return on investment for the system?

The system purchase price will have a payback on investment in 2-3 years from the 4-25% fuel savings, 2-3X extended brake life, elimination of ground tug equipment, quicker aircraft turn times and possible carbon credits.

What are the aircraft brake savings? 

It is expected that the brake savings utilizing the GTS system will reduce brake wear by over 50%. The life of carbon brakes should be increased by 2-3 times more cycles before brake replacement/refurbishment is required.

What is the cost of carrying the system per year per aircraft?

The amount of extra fuel required to carry the system weight of 200 lbs for one year per aircraft ranges from $4,000 to $12,000 per year depending on the type of aircraft, flight hours and types of routes flown. The cost to carry will be approximately 3% of the total financial savings the system provides.

How much does the system save in aircraft costs?

The system saves $250,000 to $500,000 per year per aircraft between fuel, brake wear, tug, and latency time savings in addition to its environmental benefits. See the “More Information” section of our website at

How much does the system save in emissions?

The system saves over 1987.3 Kg (4,381.2 Lbs) of CO Savings Per Aircraft Per Year.

Does the system provide benefits for military aircraft?

Yes, aircraft like the C-17 or the C-130 are often parked close to each other to assist with security often in unimproved environments. Starting the engines to taxi out can blow sand and dirt into the engines/system of aircraft parked close by and the GTS system avoids this issue. Also, tactical advantages due the low noise signature and elimination of FOD (Foreign Object Damage) engine damage increases operational readiness and tactical surprise of military aircraft.

What about helicopters?

Yes. The GTI system installed on a helicopter avoids the need for main rotors turning to taxi the aircraft eliminating the dangers to buildings, personnel and other aircraft along with a lower noise signature.


Is the Green Taxi System part of the aircraft Minimum Equipment List (MEL) and required to be operational for aircraft use? 

The GTS system is not required to be operational for aircraft use and is not an MEL item. The system totally disengaged from the aircraft when not in use or if the system not operational. If the system is disengaged or not operational the aircraft can be taxied with the main engines.

Does the Green Taxi System require special pilot training? 

The pilot steers the aircraft using the existing tiller nosewheel steering system along with the use of aircraft brakes if required. The GTI system allows for more precise speed control compared to using the main engines. An operational check out using Level A pilot training with video training and line check operational training may be used.  We believe that simulator training will not be required.

We have had chief pilots evaluate the GT system and all have determined that a video training course and an in cockpit functional check out by a check airman would be sufficient of pilot training. No simulator training is expected to be required. The GT system should increase ramp safety as the aircraft and nose gear damage caused by tug operators will be eliminated. It should increase safety as full control of the aircraft pushback under the pilots control along with their ground taxi support crew and ground crew will no longer be impacted by engine jet blast.

The pilot control panel will have a multi colored LED to indicate the system status and if the system is approaching a potential over temperature situation well in advance. We will incorporate other “heads up” indications such as overhead annunciators and/or joystick tactical feedback to the pilot in case the system reaches the “amber” temperature advising them that dynamic braking needs to be reduced well in advance of a system over temperature precautionary shut down.

Can the system be used for movement of the aircraft by maintenance crew without needing a pilot?

Yes, the system is easy to use and ground maintenance crew can be trained to use the system to move aircraft as required without needing to have a pilot on board.

What is the expected operational life of the system?

The design of the GTS is extremely robust and is expected to last the life of the aircraft in operation. The system components are designed and built to hybrid systems standards utilized on heavy truck, tank, and naval hybrid drive systems.

How many hours does it take to install the system?

The system is designed to be easily installed during aircraft build and/or retrofitting to existing aircraft during nominal C checks in two or three overnights (150 man-hours). If more time is required, it can be integrated into a heavy maintenance D check if necessary.

What are the expected maintenance costs and system reliability? 

The DC motors used by GTS are extremely reliable and have very long expected life with minimal maintenance similar to electric vehicles. However, since the distance the system moves the aircraft a relatively short distance in comparison to electric vehicles the electric motors should last the life of the aircraft with periodic inspections. Minimal maintenance can be accomplished during routine phase inspections. The ongoing operational maintenance cost of the Green Taxi system should be less than 10% of the Green Taxi aircraft savings per year.

How is the system used to back the aircraft away from the gate?

The flight crew simply activates the system in reverse mode with wing-walkers to ensure safety and can then back the aircraft away from the gate and turn in the required direction using normal aircraft steering. The GT system can be taxied in reversed up to the limiter speed of 3-5 knots (or as specified by the operator, the reverse speed can be field programmed for higher and lower speed limitations based upon the operator’s preferences. When the aircraft is taxied in reverse the pilot must not use the main brakes except in an emergency to preclude the rare potential of the nose raising up. The Standard Operating Procedures (SOP) for tugless taxi back is well established with the former reverse thrust taxi back SOP used by the airlines in the past. We believe initially that all airports and airlines will require ramp guidance personnel for reverse taxiing although we could install a camera system to assist if desired.

Since the engines can be started “on the go” the aircraft never needs to stop on the ramp or staging area allowing for shorter pushback distances/time. Airports with staging areas that require a significant tug push pushback distance this could be eliminated saving the airport/operators valuable time on the ramp.

Has an approved FAA standard operating procedure (SOP) for reverse operations been developed for the system? 

The system will leverage the previously approved SOPs that were used for reverse thrust taxi operations approved in the past. SOP development/approval will be performed in conjunction with the customers requirements and the certifying agencies.

Can the system be used to dynamically brake the aircraft during system operation?

Yes, when the main aircraft engine(s) are turned off the system provides dynamic braking and does not require the pilot to utilized the main aircraft wheel brakes. This reduces/eliminates the brake wear caused by the pilot frequently needing to use aircraft landing gear wheel braking due to the excess thrust provided by the main engines. during taxi operations. When the main aircraft engine(s) are operating the system is not operational and therefore does not provide dynamic braking.

What is the approximate taxi speed of the system?

The GTS will allow taxi speeds up to 25 Km/Hr. The average taxi speed may be faster than with existing taxi operations as the pilot will not need to brake to slow the aircraft down due to excess thrust from the main engines and then reaccelerate. It should also allow for a smoother taxi ride for passengers.

Will the pilot have an indication that the system is disconnected from the landing gear?

Yes. A light on the flight deck system controller will notify that the system is disconnected or if the system has any malfunctions.

Can the system be used in snow and icy conditions?

Yes, however for icy uphill taxiways, the main engines can and should be used to avoid slippage and steering difficulties.

Will the system affect APU (Auxiliary Power Unit) life?

No, for most airlines the APU is operated during most of the taxi time already and is running at 100% of rated RPM so there should be no significant reduction of APU life.

Can the GreenTaxi system be used while the main aircraft engines are operating?  

Yes, we expect the GreenTaxi eTaxi system to be able to be used while the engines are operating.  The key design goal will for us to use “regenerative braking” whereby we put the braking energy back into the aircraft electrical system as conditioned AC power similar to the way the starter/generators work on turbine engines.  If we can get this approved with the FAA/EASA we would be able provide braking at all times with the aircraft engines operating.  If we cannot obtain regenerated energy approval we can still provide braking with the engines operating but it may be more limited as we would need to put this excess electrical energy back into aviation grade ballast resisters which will heat up if the braking is done repeatedly.   For dynamic braking the pilot simply moves the joystick to the “reverse” position to modulate the degree of dynamic braking they desire while the main engines are operating.  


How much does the Green Taxi System weigh? 

The GT total system weight will be under 300 Kg (the Amsterdam airport specs require under 400Kg). Airbus calculations show the “cost to carry” for this weight per year per aircraft was $12,000. The Delta Airline calculations on the A220 show a “cost to carry” ranges between 8,000 Lbs- 18,000 Lbs per year per aircraft so approximately $8,000-$18,000 per year per aircraft assuming a $1.00 per Lb of Jet A.

How much weight does the Green Taxi System place on the landing gear itself? 

60-75% of the total weight is carried on the landing gear itself. The remainder is in the aircraft electronics bay and on the flight deck.

How will the system disconnect from the landing gear when not in operation?

The system will have a failsafe disconnect in the event of detection of any system failure, when the aircraft is in flight and if ground speeds are in excess of 25 knots.

Can a tow tug still be used with the GTI system installed?

Yes. The design of the GTI system and installation does not interfere with the tow tug attachments on the aircraft nose gear.

Should the system be inspected before every flight?

The GTI system should form part of the pilot’s inspection prior to each flight.

What is the expected lifespan of the system?

The GT system lifespan is in excess of the aircraft life. It will utilize similar technology and components used on heavy duty long range vehicle equipment that travels over 10,000 miles per month. Even under extreme utilization, on average the GT system will only taxi under 1,000 miles per month. As aircraft are retired the existing systems could be inspected and reinstalled on new aircraft after undergoing an overhaul process by GT.

Are there any permanent modifications affecting re-sale value of the aircraft?

In our analysis with Leibherr it is expected that no modifications to the aircraft or landing gear will be required.

What are the Operational considerations and limitations?

The GT system can be utilized for pushback from the gate without any tug required. Once the aircraft has reverse taxied back from the gate it can immediately begin to taxi to the runway without waiting for engine start thus saving the ramp latency savings of approximately 3 minutes pre aircraft cycle. It can be used for dynamic braking while taxiing allowing for the pilot to not engage the main aircraft brakes reducing/eliminating cold aircraft carbon braking snubbing that is causing the shortened life of the carbon brake system. It will accelerate quickly allowing for taxiing across active runways in a similar time then the main engines currently. It can be used for taxi back to the gate immediately after the aircraft turns off the runway and the main engines have had their required cool down period.

Any weather / meteorological / frictions’ limitations of the system?

The GT system can be used in all environmental conditions. During taxi testing we will analyze if the system is effective/safe for use when snow and ice is on the taxiway. Since the aircraft main brakes and normal nose wheet steering will still be fully operational and there would not be any differential thrust from the engines it may be found that taxiing with the GT system on snow and ice on level surfaces may be quite effective and safe. The GT system will be fully operational in snow/ice conditions and we will work with the airline operators and certification authorities to have the GT useable on snow/ice conditions.

Center of gravity impact assessment: 

The GT system helps move the Center of Gravity (CG) by moving mass forward on the nose gear. Some operators have installed ballast weight in the nose area and this could be removed with the GT system installed.

Necessary involvement from the customer:

GT will be leading and undertaking all of the efforts to achieve full FAA and EASA Supplemental Type Certificate (STC) for the complete system. The GT team has achieved over 50 STC’s in the past and are very experienced with the certification process. We would appreciate that the customer assist with GT obtain necessary engineering documentation from the OEM as required. GT would be responsible for any costs required for such documentation.

We would require the ability to do a test fit of the FAA/EASA conforming prototype GT system on the aircraft and we expect this would take at or under 7 work days and could be done during a phase inspection or during a new aircraft build to minimize any disruption to the customer’s flight operation. GT would provide 1-2 lead engineers on site and would request that the customer provide 2-3 line mechanics to perform the actual work on the aircraft. Taxi tests will be required and our initial FAA analysis shows that flight tests may not be required but that will not be determined until later in the certification process. If flight testing is required we would request that this be provided by the customer as well.

In our analysis with Leibherr it is expected that no modifications to the aircraft or landing gear will be required.