Cox shared other cost-savings that naturally come to mind, such as fuel savings, FOD cost avoidance, taxi-in/taxi-out time savings and pushback savings.
More “aggressive airlines,” Cox says, can further take advantage of engine-off operation by boarding/deboarding passenger from the rear door and through the front door.
Also, airports under morning noise curfew restrictions could create more lucrative slots.
“This can add 5-10 additional daily morning take-off slots per runway,” Cox says. “First-morning flights are the most valuable for business travelers.”
Cox expects certification of its design sometime in the first half of 2014. Six airlines, including KLM, Alitalia and El Al, have agreements to install the system on more than 285 aircraft at some point in the second quarter of 2014.
Safran and Honeywell, on the other hand, have developed an electric unit that attaches to the main landing gear.
Dubbed the “Electric Green Taxiing System,” the wheel on each main landing gear is equipped with an electric motor, reduction gearbox and clutch assembly to drive the aircraft, while unique power electronics and system controllers give pilots total control of the aircraft’s speed and direction during taxi operations.
Each unit of the Honeywell system, including the motor, gearbox and clutch weighs about 220 pounds or a total of more than 800 pounds.
“EGTS will be for aviation what hybrid cars were for the automotive industry,” says Brian Wenig, EGTS program vice president, Honeywell Aerospace. “The potential of fuel savings and emissions reductions that can be had with the system will be monumental for airlines.”
According to the joint venture, a short- or medium-range aircraft spends up to 2.5 hours of its time on taxiways every day. As a result, the EGTS could save approximately 600 kilograms of fuel used during taxiing from being consumed daily, according to Honeywell and Safran estimates.
Based on standard taxiing procedures for a narrow-body aircraft, the company says the system will save up to 4 percent in block fuel costs and reduce carbon emissions by 75 percent, a particularly important issue at European airports due to EU carbon taxes.
The main advantage of placing the system in the main landing gear is traction. The companies say less than 10 percent of an aircraft’s weight is on the nose gear, which makes the landing gear a better place to handle adverse conditions on the ground. (For its part, WheelTug says it has tested its system in less than optimal weather conditions and seen no problem.)
Since the system is situated in the landing gear and represents a structural change to the airframe, the company primarily takes an OEM approach to marketing the system, although it says retrofits are a possibility.
According to a Wall Street Journal report published last June, the joint venture has already invested about $250 million into the concept and built 15 systems that have been put through 3,000 hours of testing.
During the air show last June, the joint venture announced an extended collaboration on the development of the EGTS with AirFrance.
“At Air France,” says Bruno Delile, senior vice president, new aircraft and corporate fleet planning for the airline, “we are particularly conscious about energy efficiency. With the electric green taxiing system, we aim to reduce our fleet’s carbon footprint at airports, while also decreasing noise and useless fuel consumption.”