The flight from Bengaluru to Phoenix, had two major stopovers – at Charles De Gaulle Airport in Paris and Atlanta International Airport. At both the airports, the aircraft taxiing time was fairly long as the airports are huge and traffic density is high. It was clear that the aircraft was burning substantial quantities of precious aviation turbine fuel while taxiing. Once at Honeywell Aerospace facility, being the sole representative from India among the 30 from the international media, it was comforting to know that Honeywell was working on several technologies to make air travel comfortable, safe, secure, low-cost and environment-friendly. The international media got a peek into what Jim Fusaro, Vice President, Honeywell Aerospace, calls ‘transformational type of product in aviation’ – the Electric Green Taxing System (EGTS). Research is progressing at a frenetic pace by Honeywell and Safran jointly, to introduce EGTS by 2017.

Fusaro pointed out that there would be substantial savings on fuel and his guestimate was that one narrow-body aircraft would save about $2,00,000 worth of fuel for an airline in a year, if the average taxiing time per sortie is taken at 20 minutes. Fusaro said that it would be an option that the original equipment manufacturers (OEMs) offer to airline operators and going by the savings prospects, the assessment is that it would become a norm.

With oil prices are expected to remain at record levels and with the persistent volatility in the market, airlines continue to look for new ways to save fuel and reduce cost of operations. Fuel costs are an ever-increasing drain on airline revenues – accounting for around 45 per cent of direct operating costs.

Fuel Consumed in Taxiing

Taxiing operations represent up to six per cent of total fuel consumption for short-haul fleets operating single-aisle aircraft from congested airports. A single-aisle aircraft operates an average 2.3 hours on the ground during eight to ten daily rotations. In fact, the global family of short-haul aircraft burns around five million tonnes of fuel per year during taxiing operations alone. This also amounts to an output of around 13 million tonnes of carbon dioxide each year. Despite the introduction of more fuel-efficient and less polluting turbofan and turboprop engines, the rapid growth of air travel in recent years has contributed to an increase in total pollution attributable to aviation. Research efforts are directed towards reducing fuel burn and being environment-friendly.

Doing Away With Tugs

The reliance on tugs for aircraft pushback can often result in delay. Milan Cornelsen, Director Fleet and Asset Management TUIfly, explained, “Electric taxiing would bring independence and fuel reduction to our fleet. Independence, as we will not need any push-back cart at any outstations and destinations.If the push-back cart is defective or occupied or the driver is on strike, our passengers currently have to wait for their departure. With an electric taxi system we would just need the marshal to help guide us.” Any solution that could eliminate the need for tugs is an added bonus and would make the dispatch process faster and more autonomous.

The benefits to passengers of a tug-less approach to aircraft dispatches would be faster turnaround. And if the aircraft’s engines were not running when the aircraft arrives at the gate, ground-handling staff would be able to access the aircraft more quickly as well as disembark passengers and off-load baggage faster. The need for an alternative solution to traditional aircraft taxiing operations, which reduces fuel burn and delivers environmental benefits, is now greater than ever. As a result, a number of initiatives are underway to develop electric taxi solutions, an effort that has been going on since the oil crisis of the 1970s.Currently both Boeing and Airbus are exploring possibilities of autonomous taxiing solutions and there are a number of these being brought to the market.

Honeywell, Safran Initiative

In 2011, Honeywell and Safran joined forces to develop an innovative solution, the EGTS, that can significantly improve an airline’s operational efficiency, reducing fuel and other taxiing-related costs. It also provides environmental benefits by slashing carbon and other emissions created during ground operations. EGTS combines Safran’s extensive experience in integrated landing gear systems with Honeywell’s heritage in auxiliary power unit (APU) innovation. Their combined experience gives airlines an attractive proposition and represents a viable and credible solution when it becomes available in 2017.

EGTS uses power from the aircraft’s APU generator to drive electric motors connected to the main landing gear wheels. The system allows an aircraft to pushback without tug assistance and taxi to the runway without the main engines running. The main engines are started just before the aircraft enters the runway. On clearing the runway after landing, the the main engines are shut down. The aircraft can then taxi to the parking gate using EGTS.

Today’s turbofan engines are optimised for flying, not for powering aircraft on the ground. To taxi between gate and runway, an airliner burns sizeable quantity of fuel. This problem is more acute with short- and medium-haul aircraft that spend relatively longer time taxiing between runway and gate, as against time in the air.

Michel Laudy, Short and Medium Haul Fleet Director, Air France–KLM, hopes that electric taxiing would be a major boon. “Green taxiing could add some value to Air France. At Paris Charles De Gaulle (CDG) airport we typically have around 70 single-aisle aircraft operating on routes less than 500 nautical miles every day and the time per aircraft for manoeuvring on ground averages 17 minutes. At Orly (ORY) it is around ten minutes. The fuel savings with an electric solution would be significant. It would also give greater autonomy to the aircraft and reduce handling costs.”

Noise Levels

EGTS would also have a considerable impact on airport noise and emission levels, offering a reduction of up to 75 per cent in carbon (CO2/HC/CO) and up to 50 per cent Nitrogen Oxide (NOx) emissions. Michel Laudy said that with both CDG and ORY being close to Paris, any reduction in emissions and noise would be vitally important. “Among the options on a new Airbus aircraft, a green taxi solution would certainly be worth considering.”Airbus A-320 Captain, Uwe Leberl of Lufthansa AG believes that the benefits of an e-taxi solution are wide-ranging in terms of fuel saving, drastically reduced push-back charges, reduced emissions and noise. “This sends a signal out to the world that something is being done to reduce the impact of our industry on the environment.”

He added, “We have around 90 aircraft that could benefit from an electric taxi solution. There are still some aspects that I would like to know more about, such as the human-machine interface for operating such a system, but in principle, I think, it is a good idea. I think the time savings in what would have been the push-back phase are also worth considering – it would certainly accelerate the process.

Advantages Galore

An e-taxi solution would require a significant change to the workflow required to dispatch an aircraft, including Air Traffic Control (ATC) procedures and that needs to be carefully considered. Alain Chapgier, Corporate Strategy Manager at Aéroports de Paris, said that an autonomous e-taxi solution brought other benefits too. “Such a system would work at any airport, both during the dispatch and landing phases. It could also be used to move aircraft to maintenance facilities or parking stands as well. This saves time and money for both the airline and the airport handling teams. “As our average airport taxi-out time is around 25 minutes in total, we think that any solution must have certain minimum parameters, such as a taxi speed of at least 20 knots with good acceleration up to 10 knots. It must also be able to deal with slopes and have good integration with the aircraft’s existing systems.”

And there are other benefits too. Line maintenance time would be lowered because brake wear will be reduced and engine life extended. Engines are prone to ingest large amounts of dust and debris when powering up on the ground at an airport. With EGTS the problem is reduced considerably.

The project has received a lot of interest from the aviation industry. James Crites, Executive Vice President of Operations at Dallas/Fort Worth Airport, said, “When I first saw the presentation on electric taxiing I thought this was potentially another tool that we could consider to address the emissions challenge that we all face.” Apart from the environmental benefits it is also attractive in terms of reducing operating costs. Damage and injury caused by debris and equipment blown by engines being run up on the ramp would also be eliminated,” he said.

Honeywell, Safran Synergies

The EGTS initiative was first announced at the Paris Airshow in June 2011, where Honeywell and Safran signed a memorandum of understanding to create a joint venture company called EGTS International to deliver innovative new electric green taxiing system solutions for new and existing aircraft. The joint venture encompasses joint system development, production, marketing and support.

The partnership provides systems expertise with a combined over eight years of electric taxi research and development experience. This combines Honeywell’s extensive knowledge of avionics and auxiliary power systems with Safran expertise in landing gear systems. Both bring complementary capabilities in terms of electric power products and systems integration, calling on the expertise of more than 200 engineers at 16 locations worldwide, from France, the US, Canada, UK, India and Mexico.

So, how does it work? Using the APU generator to power electric motors integrated into main landing gear, the EGTS system allows aircraft to push-back autonomously from the gate without the need for a tug and taxi between gate and runway without requiring the use of aircraft engines. Two of the main wheels are equipped with an electric motor, reduction gearbox and clutch assembly to drive the aircraft. The main landing gear wheels were chosen for maximised performance, traction and agility.

Olivier Savin, EGTS Program Vice President at Safran, explained, “The primary driver for powering the main wheels rather than the nose wheel is traction. Less than ten per cent of the aircraft weight is on the aircraft nose gear making it difficult to achieve the taxi performance required by airlines in all operating conditions. The EGTS will work on any type of taxiway condition – rain, ice or snow, where greater tire ground friction is required.” Each of the aircraft’s powered wheels is equipped with an electro-mechanical actuator, while power electronics and system controllers give pilots total control of the aircraft’s speed and direction during taxi operations.

The initial EGTS tests were completed in Montpellier, France, on an Airbus A320. The tests were to evaluate runway conditions and calculate the necessary loads needed for moving the aircraft on the ground. Brian Wenig, EGTS Program Vice President at Honeywell, explained further, “What became clear was that the decision to power the main wheels and not the nose wheels was the right one. Under certain conditions such as when the ground is icy, wet or there is an incline, poor adhesion (grip) can occur if the front wheels are driven. But when mounted on the main landing gear wheels, closer to the aircraft’s centre of gravity, the problem is eliminated.”

The big benefit of EGTS is that it is a fully-integrated solution, including the cockpit interface, controls, APU integration, wheel mounted motors, actuators and much more.