ELECTRIC GREEN TAXIING SYSTEM
New technologies promise cost saving and enhanced safety
Written by Brian Dunn
Operators of all sizes are always searching for ways to cut costs and improve safety: thanks to several emerging technologies, goals of fiscal responsibility and more refined operations are more attainable than ever.
For example, as part of an upgrade of the U.S. air-traffic system, the Federal Aviation Administration (FAA) formed the Surveillance and Broadcast Services program office in 2005. The program office will change the country’s air traffic control system from one that relies on radar technology to one that uses precise location data from the global satellite network.
|Honeywell’s Electric Green Taxiing System would replace the tugs that currently push aircraft away from the gate so the main jet engines can power up safely to taxi down taxiways. PHOTO: HONEYWELL
Enabling this move is a proven technology called Automatic Dependent Surveillance-Broadcast (ADS-B). ADS-B is a crucial component of the country’s Next-Generation Air Transportation System. With ADS-B, both pilots and controllers can see radar-like displays of traffic and the displays update in next to real time and do not degrade with distance or terrain. The system also gives pilots access to weather services and flight information services.
While radar technology works well over most land where there are plenty of radar stations, there is no radar over mountain ranges or the oceans. Therefore, planes traveling in remote areas have to follow established routes and stay more than 50 nautical miles apart, making it harder for them to climb to higher altitudes for a more efficient fuel burn.
New GPS systems installed in aircraft will send out its location every second compared with once every four to 12 seconds currently which will help controllers guide traffic with more precision.
Canada is currently developing a number of navigation specifications for performance-based navigation (PBN) based on the latest issue of the International Civil Aviation Organization (ICAO) PBN manual. The development of these navigation specifications is in line with the development of the same provisions in other ICAO member countries. Some of these navigation specifications are also based on GPS.
United Airlines is taking the technology a step further to reduce its reliance on controllers and increase the efficiency of its routes.
The company is testing equipment that captures the location of all aircraft within 200 nautical miles on a screen in the cockpit. The SmartTraffic System is made by Honeywell International and allows pilots to manoeuvre closer to other planes. That means they can take more efficient paths to their destinations.
“The system allows aircraft to climb through each other’s altitude to fly at more efficient altitudes which saves time and fuel,” explained Robert Witwer, vice-president of advanced technology at Honey-well of Morristown, N.J. The downside is that longer flights have to fly at lower levels initially to burn off enough fuel before they can climb to a higher altitude.
United Airlines is testing technology that shows controllers and pilots exact locations of aircraft which can safely be separated by only 15 nautical miles, giving pilots the option to take more efficient routes. And some lower altitudes may be better than higher ones due to winds and severe weather, said Witwer.
Pilots using the SmartTraffic System on overseas flights would need to receive permission from controllers to change altitudes, but the 15 nautical miles of nautical separation from other aircraft is more than two-thirds less than the current spacing required by the FAA. Having a better picture of air traffic may also improve safety during emergencies and storms, when flight paths may be changed. United estimates that each year it can save an average of $190,000 for each plane that flies international routes. “Flight trials are expected to continue until the end of 2013 and the results will determine our path to the (commercial) market,” said Witwer.
Domestically, ADS-B commenced in January 2009 with 250,000 square nautical miles of airspace over Hudson Bay in Northern Canada. About 35,000 flights a year use this airspace with the majority of flights linking Europe and North America. Others transit to Asia, including those using polar tracks.
ADS-B has enabled reduction of the separation minima for aircraft properly equipped and accordingly allows more aircraft to follow the most efficient flight trajectory. Controllers currently use ADS-B tactically, by applying reduced separation between so equipped aircraft on an “opportunity basis” within the Hudson and Minto sectors. This means each aircraft will have the appropriate protected airspace around it applied based on its capability.
In March 2012, NAV CANADA extended its surveillance to cover a 1.3-million-square-kilometre portion of airspace over the North Atlantic, the busiest oceanic airspace in the world. ADS-B surveillance has enabled the Gander Area Control Centre to safely reduce separation standards for properly equipped aircraft from approximately 80 nautical miles (NM) to initially 10 NM. This gives air traffic controllers greater ability to provide aircraft with more cost-effective flight profiles, including earlier climbs to fuel-efficient altitudes.
In the U.S. model, another consideration and benefit is that the ground stations used for ADS-B are much smaller, take up less land and require virtually no maintenance. This has – or will – result in serious cost savings to the ATC budgets. One can optimistically hope that such savings will help to reduce operator/user fees.
Last July, Iridium Communications and NAV CANADA announced a planned joint venture. This new relationship promises to offer worldwide ADS-B-based air traffic surveillance services using the upcoming Iridium “Next” satellite network. These satellites begin launching in 2015 and will be completed in 2017.
The Iridium-NAV CANADA joint venture, called Aireon, will add 1090ES ADS-B receivers to each of the 66 satellites (and backups) destined to form the Iridium “Next” constellation. The low-earth-orbiting Iridium satellites will offer worldwide coverage, including polar regions, and with the ADS-B payloads will provide complete visibility to all aircraft everywhere, helping air navigation service providers (ANSPs) decrease inefficiencies. This new capability will extend the benefits of current radar-based surveillance systems, which cover less than 10 per cent of the world, to the entire planet.” Aireon is expected to become operational in 2018 – two years before the FAA’s ADS-B out equipage mandate takes effect.
ADS-B ground stations are currently being installed worldwide, with the entire U.S. airspace expected to be covered by next year.
There is, however, no way to provide surveillance over oceans or remote areas that lack radar coverage without using satellite communications. Aircraft are already broadcasting GPS-derived position information over satellite networks on oceanic routes. The Aireon system adds the ADS-B ground station type technology to a worldwide satellite network and makes it possible to deliver comprehensive surveillance data to ANSPs like NAV CANADA that plan to work with Aireon.
Moving in a new direction
In addition to its role in the expansion of ADS-B, Honeywell is working on another cost-saving project in conjunction with Safran SA of France that could save upwards of $200,000 per aircraft per year. The technology is called the Electric Green Taxiing System and it would replace the tugs that currently push aircraft away from the gate so the main jet engines can power up safely to taxi down taxiways.
Honeywell, among other manufacturers, is devising electric motors that weigh about as much as a V-8 engine strong enough to move 180,000-pound (81,650-kilogram) jets, letting pilots taxi without relying on main engines or diesel tugs.
Using the Auxiliary Power Unit (APU) generator to power motors in the main wheels, each of the aircraft’s powered wheels is equipped with an electromechanical actuator, while unique power electronics and system controllers give pilots total control of the aircraft’s speed, direction and braking during taxi operations.
Taxiing on electric power is an example of how technology, in this case motors so small they fit in the hub of a jet’s nose wheel, can revolutionize something as routine as an airliner’s journey between the terminal and the runway.
Aircraft equipped with the system will be able to “pushback and go” more quickly, thereby reducing both gate and tarmac congestion, improving on-time departure performance and saving valuable time on the ground.
The Electric Green Taxiing System greatly reduces engine emissions, thereby reducing a key emissions source for airports’ impact on air quality. In addition to eliminating the need for aircraft pushback and towing via tug tractor, it also reduces brake wear, extends main engine life, improves ground crew safety and reduces noise in the airport environment.
While the SmartTraffic System is focused on transcontinental routes, the Green Taxi shows more value for short-haul aircraft like the Boeing 737 or Airbus A320 which do a lot of turnarounds in a day, Witwer pointed out.
As taxi operations burn a significant amount of fuel (as much as five million tons of fuel per year for short-haul aircraft), the Electric Green Taxiing System can result in savings of up to four per cent of total block fuel consumption.
“Short hauls do a lot of taxiing time, especially in a place like Newark, where you can be 20th in line,” said Witwer. “And there are a number of airports in Europe that have tough emission standards that would make the Green Taxiing System appealing. I believe it’s a game-changing technology. It’s hard to imagine that 10 or 20 years from now that we’ll still be using jet propulsion engines to propel aircraft around airports.”
The first public demonstration of the Electric Green Taxiing System will occur at the Paris Air Show in June on a Safran A320 aircraft. The system, either for new aircraft or as a retrofit solution to in-service aircraft, could be available as early as 2016, according to Witwer.
The prospect of annual savings of $200,000 per jet from lower fuel use and less ground time has sparked interest from Airbus and airlines such as EasyJet and Alitalia. Airlines face the highest sustained prices ever for jet fuel. United Continental, the world’s biggest carrier, says it burns $25,000 of fuel per minute. Jet fuel delivery in New York averaged $3.12 per gallon in 2012, more than four times as much as a decade ago.
Taxiing on one engine has become a common fuel-saving practice for twin-engine jets in recent years and planes already make electricity when they’re at the gate by running small turbine engines or APUs. What’s new in today’s technology is the convergence of airlines’ search for more efficiency and recent advances in miniaturizing electric motors to propel a plane at the 32 kilometres per hour it may need for taxiing.
The Honeywell-Safran team estimated its unit would weigh a maximum of 880 pounds, while startup WheelTug Plc of Gibraltar said its electric-taxi technology is only about 300 pounds. Another entry, a venture between L-3 Communications Holdings Inc., New York, and Crane Co., Stamford, Ct., isn’t commenting on its system.
WheelTug’s motor fits in the hub of a jet’s front wheel and is just five inches wide, according to chief executive officer Isaiah Cox. That’s half as wide as it was two years ago, when the company still had to attach the motors outside the hub.
Cox compares it to packaging an elephant into the nose wheel of an aircraft. It would not only eliminate the cost of a pushback from a tug that runs between $50 and $150, but also the consumption of about 55 gallons of fuel taxiing before and after takeoff, based on average burn rates and ground times at U.S. airports, Cox noted.
WheelTug said its system may save about $500,000 per plane annually, including benefits such as less wear on engines. Honeywell and Safran said their savings may exceed $200,000 per plane per year by paring fuel use and ground time and eliminating charges for tug services. Crane also said taxiing on electricity would cut noise, reduce emissions and shrink the risk of having a jet’s main engines damaged by tarmac debris.
Combining small electric motors and new cockpit controls won’t be the only challenge for Honeywell and its rivals. Suppliers will have to convince airlines that the savings will outweigh the extra fuel burned in flight from the equipment’s added weight.
As operator costs continue to increase and companies continue to find ways for be more fiscally responsible, it’s encouraging to see company’s such as Rockwell Collins, Honeywell, Iridium Communications, Safran, L-3 Communications, NAV CANADA and more developing real solutions for challenging situations.
– With files from Rob Seaman