Thursday, December 26, 2013

Tow to runway by electeric tug

Can a vehicle that looks like a tow truck crossed with a Prius improve commercial aviation and air quality?
Airplanes burn a lot of jet fuel using engines to drive between terminals and runways, adding to polluting emissions and costing airlines money in fuel and maintenance. The airline industry is trying to develop electric-powered alternatives, both on and off the plane.
For passengers, this could mean that soon the anxious, slow trip to the end of the runway before takeoff may be silent—and come after less waiting.
An electric-powered tug that can be controlled by the captain in the cockpit is being tested here. Lufthansa hopes to start putting it in regular passenger-flight service next year.
Called "TaxiBot", it slides under an airplane's nose wheel and tows the plane, steered by the pilot moving the nose wheel just as if the plane were taxiing under its own power using its engines. An aviation startup is testing a new kind of motorized wheel to move the plane on the ground. And a partnership of two big aerospace firms, is testing the two main wheels of another motorized wheels system for single-aisle planes.
"You're starting to see quite a push in aviation for green initiatives," said Honeywell Vice President Brian Wenig.
Lufthansa has been testing TaxiBot since May at Frankfurt International Airport in the middle of the night, when the airport's flight curfew curtails other activity. The vehicle, developed by Israel Aerospace Industries, looks just like the souped-up tractors that push and pull airplanes into and out of gate areas.
But the TaxiBot is really a robotic tow truck for planes. It has a safety driver onboard who makes the coupling with the plane. The tug drives up to the nose wheel and raises it off the ground. The plane and tractor brake using the airplane's brakes. And each tug has its own navigation system, accurate to about 1 foot. It knows the airport and can help guide planes, automatically slowing down when a sharp curve is ahead so there is less wear on brakes.
The TaxiBot, which will cost at least $1 million for the smaller version and perhaps twice as much for a bigger model capable of towing jumbo jets, has the advantage of being completely separate from the plane. There are no motors or equipment to install on jets that add weight and increase fuel burn.
The average taxi-time in Frankfurt is 10 to 12 minutes. Gerhard Baumgarten, director of marketing in Lufthansa's engineering unit, says the net savings using TaxiBot to deliver a 737 to an area near the end of the runway is about 35 gallons of jet fuel, which costs more than $100 at today's prices.
For an Airbus A380 superjumbo jet on a 10-minute taxi, TaxiBot would cut 95% of the fuel burn, or a net savings on each departure of about 130 gallons of jet fuel costing nearly $400.
Airlines also stand to save on maintenance, since engine overhauls are scheduled based on hours of use. Brakes would get less wear. And damage from litter around airport terminals that gets sucked into engines should drop since engines won't be starting by the terminal.
Starting aircraft engines at a holding area near the runway instead of around the terminal also saves time. Often planes block alleys and gates while they start engines, leaving other planes sitting with engines burning fuel.
Engineers are working to fine-tune the system, Mr. Baumgarten said, so pilots feel no difference between their engines and a TaxiBot tow. "We are not there, but we are getting closer and closer," he said.
New Competition for Tugs
Honeywell and Safran say their competing Electric Green Taxiing System, or EGTS, should be ready for airline service in 2017. That system has some big supporters: Airbus and Air France have both signed as partners.
"Electric motors are not complex, but it is a new system added to aircraft and it needs to fully integrate into aircraft," said Mr. Wenig, who oversees EGTS at Honeywell. The system must undergo lots more testing and win certification from regulators like the Federal Aviation Administration.
EGTS, which was demonstrated on an aircraft at last summer's Paris Air Show, uses electric motors mounted on the main landing-gear wheels under the center of a plane. The motors can back the plane away from gates and taxi it to the end of a runway with the pilot using the plane's tiller to steer. "It will reduce or eliminate tugs," Mr. Wenig said.
Beyond the environmental benefits, the system would speed up departures, since planes—and passengers—wouldn't have to wait for pushback tugs to decouple and get out of the way.
Mr. Wenig says EGTS only makes sense for single-aisle aircraft like the Airbus A320 or Boeing 737. Wide-body jets would require bigger electric motors on the wheels and they typically fly long trips with relatively little time each day taxiing on the ground.
Fuel burned to carry the extra weight would nullify any savings from using the electric motors at the airport. But smaller planes tend to fly short trips all day long and spend a lot of time on the ground. EGTS will add about 700 pounds to the weight of airplanes, but each flight can carry less fuel since it won't be needed for taxiing.
Mr. Wenig estimates fuel savings of about 4% from not using engines during taxi. Honeywell said airlines could save about $200,000 a year on each aircraft with EGTS.
Sideways Parking Job
WheelTug, the brainchild of startup company WheelTug PLC, is an electric-powered nose wheel installed on planes that replaces existing nose wheels. The system's savings come not from lower fuel burn but from quicker maneuvering on the ground. Planes can park sideways to terminals and unload and load from rear doors as well as front because there's no exhaust blast from engines.
Thirteen airlines—most of them low-cost discount carriers like Mexican airline Volaris—have reserved delivery positions for 731 aircraft, said Isaiah Cox, WheelTug's chief executive. He thinks the system will enter service in 2015, FAA-permitting. One attraction: WheelTug is offering the system free in exchange for a promise to pay the company half of what the airline saves.
That savings can come in many forms beyond lower fuel burn. Mr. Cox figures less time spent at gates means airlines will be able to operate more flights per day. In addition, WheelTug could let airlines squeeze in an extra takeoff at airports with curfews. If the curfew bans starting engines before 5 a.m., for example, a WheelTug-equipped plane could be waiting at the end of the runway to start engines at 5 a.m. and take off while other airplanes were still back at gates waiting to start engines.
"It guarantees first flight out," he said.
 (Scott McCartney - The Wall Street Journal) 

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