Continuous Descent: Saving Fuel and Reducing Noise for Airliners

Airline passengers arriving in Atlanta on early morning “redeye” flights during the past few months may have noticed something different during their descent to the runway. Instead of the typical sound of engine power rising and falling as the aircraft descended in a series of level flight steps, they may have noticed a quieter arrival – without the steps.

The changes were part of Georgia Tech’s flight-testing of “continuous descent arrivals,” a procedure designed to save fuel and time while producing environmental benefits by reducing both noise and emissions. Involving more than 600 flights, the Atlanta study was done in collaboration with the Federal Aviation Administration (FAA), FedEx and Atlanta’s two dominant air carriers: Delta Air Lines and AirTran Airways.

The continuous descent arrival procedure has already been studied at Louisville and Los Angeles airports. Proponents hope the 90-day test at Hartsfield-Jackson Atlanta International Airport – currently the nation’s busiest airport – will move the concept one step closer to nationwide implementation. Estimates suggest that continuous descent arrivals could save a large airline as much as $80 million per year in fuel costs alone.

“In commercial aircraft, we see anywhere between 300 and 1,000 pounds of fuel saved for each arrival,” said John-Paul Clarke, director of the Air Transportation Laboratory at Georgia Tech and an associate professor in the School of Aerospace Engineering. “With fuel cost at $3 per gallon, that would amount to as much as $600 per arrival and could really add up for the airlines at a time when they need all the savings they can get.”

Because aircraft engines don’t throttle up and down during a continuous descent arrival, there are also significant reductions in noise and emissions. Keeping engines at idle power can cut emissions of nitrogen oxides by nearly a third, and reduce noise by 6 decibels along certain portions of the flight path – both significant reductions that would improve the environment in the vicinity of airports.

And the technique could cut two minutes off the approach and landing portion of a flight. While that doesn’t seem like much, it could result in more efficient utilization of aircraft and reductions in flight times for crews.

Hartsfield-Jackson Atlanta International Airport is the nation’s busiest.

Continuous descent arrival is one in a series of improvements aimed at creating the next generation of air transportation technologies. The goal is to redesign the airspace to allow future airliners to travel the most efficient paths to their destinations.

Though the final numbers from the Atlanta evaluation won’t be known for several months, the potential savings have been demonstrated by more than 60,000 landings at Los Angeles with a continuous descent arrival technique developed by Georgia Tech. But adopting the procedure throughout the airspace system won’t be easy. Safety considerations must be paramount, and there are a number of optimization challenges caused by widely varying aircraft types, wind conditions and airport configurations.

“Imagine a line of aircraft descending through a long tube that’s fixed laterally and limited vertically to be within a narrow band,” explained Clarke. “If each airplane were like a ball with a different coefficient of friction, then when you put the balls in the tube at equal intervals, they would begin to catch up with one another. The ball with the lower coefficient would tend to catch up with the ball with a higher coefficient. That’s something that we have to work very hard to avoid.”

While the risks of getting aircraft too close are obvious – and governed by FAA rules on minimum spacing – too much spacing between landing aircraft can waste time and reduce airport throughput.

“The goal is to design a procedure that allows the aircraft engines to throttle back to idle power at the point of initial descent and to remain at idle power along the flight path to the runway as long as possible,“ Clarke added. “We have figured out how to put altitude and speed constraints along the flight path so they can stay at idle power as long as possible while achieving the required minimal spacing at the runway threshold.”

Determining those constraints requires detailed knowledge of the performance of each aircraft type in use. Clarke and his research team have obtained performance data for most Boeing aircraft, as well as some of those manufactured by Airbus. Based on the performance data, they have simulated the operation of each aircraft type under varying wind and weight conditions.

The researchers have also modeled variation in pilot behavior, because small differences in when flaps are deployed and landing gear lowered create variations in speed, which affect aircraft spacing.

Arrivals would be customized for each airport, taking into account wind and traffic patterns. And because the spacing between aircraft is determined well before they arrive at their destinations, adoption of the technique will require changes in the nation’s air traffic control system.

“The air traffic control system currently isn’t designed to allow the kind of fine-tuning we need, but I’m very optimistic about being able to change that,” said Clarke. “Throughout all the areas, the FAA and the airlines, there is a growing acceptance that this is a solution. We have been able to do the analysis, the flight-testing and the number crunching to show that it can be done.”

Clarke, who began the research at the Massachusetts Institute of Technology before joining Georgia Tech in 2005, believes the cost savings will ensure adoption of continuous descent arrivals. He compared the technique to the adoption of fuel-saving winglets, small vertical attachments that have replaced traditional wingtips on many aircraft.

“For years people knew that winglets provided better performance, but it costs money to install them,” he added. “When fuel got more expensive, airlines started installing winglets because the savings justified the costs. The benefits of continuous descent arrival may also take some time to be realized.”

This article originally appeared in the Fall 2008 issue of Research Horizons, Georgia Tech’s research magazine.

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Governor Releases Monday Fuel Update

Governor also sends letter to President Bush asking for release of crude from reserve

Governor Sonny Perdue today released the latest information on fuel production from the Gulf of Mexico:

Power outages – There are still more than 154,000 people without power in Texas. Crews are making rapid progress restoring power – about 415,000 people were reported without power on Friday.

Percent “shut-in” – The U.S. Department of Energy reports 57.4 percent of crude oil production capacity in the Gulf of Mexico is out. This is a slight improvement from Friday, when 59.3 percent of capacity was out. On Monday, September 22, 89.2 percent of capacity was out.

Refineries – Only two refineries remain completely shut down, and three additional refineries are “back to normal” compared to Friday’s report.

On September 27, the Department of Energy (DOE) announced that it is delivering 500,000 barrels of emergency exchange oil to Marathon’s Midwest refineries via the Capline.

Also today, Governor Perdue requested President George W. Bush direct the Department of Energy release a significant amount of crude oil from the Strategic Petroleum Reserve (SPR).

“As President Bush and Congress work on a plan to rescue our financial markets, I urge them to also focus on our fuel shortage in the Southeast,” Governor Perdue said. “As refinery capacity is returning to pre-hurricane levels, I believe a surge in crude from the Reserve would bridge the gap until full production resumes and lessen the impact of shortages on the daily lives of our citizens.”

To date, DOE has released more than 4 million barrels of oil from the SPR. While it would take time for the crude to be processed by refineries and shipped to the Metro Atlanta market, release of the reserve would ensure fuel supplies continue to rise.

More than 1,000 Georgians have used a new tool at the Georgia Environmental Authorities Authority’s website that provides drivers with information about gas prices and gas availability. Consumers can access this information by going www.gefa.org and looking under the News and Notices section.

Some practical fuel efficiency tips for drivers include:

· Drive sensibly: Speeding, rapid acceleration (jackrabbit starts), and rapid braking lowers gas mileage.
· Choose the right vehicle: If you own more than one vehicle, drive the one that gets better gas mileage whenever possible.
· Decrease speed: Gas mileage decreases rapidly when driving more than 60 miles-per-hour.
· Avoid idling: Idling gets zero miles per gallon. Cars with larger engines typically waste more gas while idling than cars with smaller engines.
· Commute alternatives are also a useful way to conserve fuel, including telework, carpool and transit options, and flexible work schedules. More information is available about commute alternatives at www.CleanAirCampaign.com.

These figures above come from the Department of Energy’s daily situation report. The complete report is available at: http://www.oe.netl.doe.gov/docs/2008_SitRep_20_Ike_092908_12PM.pdf .

Letter to President Bush:

September 29, 2008
The President
The White House
Washington, D.C. 20500

Dear Mr. President:

As you are personally aware, over the last month we have seen Hurricanes Gustav and Ike crash into the United States Gulf Coast. These natural disasters devastated coastal areas in both Texas and Louisiana, damaging the lives of citizens in both states. Under your direction, the Department of Homeland Security (DHS) and the Federal Emergency Management Agency (FEMA) have worked tirelessly to help residents pick up the pieces. Our thoughts and prayers remain with these citizens as they begin to rebuild their lives.

While the damage on the Coast was extensive, the ripple effect of the direct hit to the petroleum industry is still impacting the lives of citizens around the Southeast. In Georgia, which is almost completely reliant on fuel transported from refineries in the Gulf via pipeline, we are particularly impacted by outages in the fuel supply chain.

I have watched with interest as you and Congress continue to work around the clock to rescue the financial markets and slow the impact of banking failures on the U.S and global economies. As Congress moves to vote on the rescue plan, I would ask that you also focus your attention on the fuel shortage in the Southeast that is impacting state and local economies. Gas stations with no fuel in the ground coupled with long lines at stations with current supply have become commonplace in Metro Atlanta and other places around the state. It is obvious that we are facing a true gap in the supply chain and I ask that you consider releasing a significant amount of crude oil from the strategic petroleum reserve (the Reserve) to refineries in the Gulf to help bring the system back on line.

I would like to thank you for your move earlier this month to make crude oil supplies from the Reserve available to the market. Timely releases have lessened the impact of production losses in the Gulf. Now, as refinery capacity is returning to pre-hurricane levels, I believe a surge in crude from the Reserve would bridge the gap until full production resumes and lessen the impact of shortages on the daily lives of our citizens.

In Georgia, we have made decisive moves to curb demand and assist distributors as they work to increase supply. My administration worked closely with the Environmental Protection Agency (EPA) and Administrator Johnson to secure three different fuel standard waivers. Those waivers are allowing distributors to more easily import additional supplies. We have issued an executive order activating Georgia’s price gouging statues, and have eased requirements on the size and weight of fuel shipments and the number of operating hours for trucks bringing supply into the state. We have teamed up with the private sector to provide information to our citizens about the realtime locations of available fuel. I continue to encourage Georgians to conserve gas by teleworking, carpooling, using mass transit and other measures to help us through this short-term supply deficiency.

While these actions have helped, I am confident that a release from the Reserve is critical and will give our citizens confidence that additional supplies are forthcoming. Thank you for your time and attention on this important matter.

Respectfully,
Sonny Perdue

Cc: Secretary Samuel W. Bodman
Georgia Congressional Delegation

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Georgia Schoolchildren Strike Gold with King Tut Exhibition Field Trip Assistance Initiative

PRNewswire/ -- In an effort to offset rising fuel prices that are a deterrent to school field trips, Georgia's State Superintendent of Schools Kathy Cox, along with organizers of "Tutankhamun: The Golden King and the Great Pharaohs," announced that $200,000 in fuel will be made available to Georgia schools to assist with classroom visits to the exhibition, and up to 10,000 students will receive free entrance. The initiative is being made possible through the support of RaceTrac Petroleum, the third largest private company in Georgia. RaceTrac operates more than 525 retail gasoline convenience stores in 12 southeastern states.

The U.S. premiere of the exhibition at the Boisfeuillet Jones Atlanta Civic Center will be presented by the Michael C. Carlos Museum of Emory University from November 15, 2008 to May 25, 2009. To further supplement classroom visits, a robust portfolio of educational content and lesson planning materials developed by the Carlos Museum is available for free at http://www.kingtut.org/ or http://www.carlos.emory.edu/teacher-programs.

According to a survey by the American Association of School Administrators (AASA), released July 29, almost half of school districts nationwide are cutting back on field trips due to rising transportation costs.

"This is a perfect example of how the business community can support the education of children," said State Superintendent of Schools Kathy Cox. "The King Tut exhibit will allow students to see history and science firsthand, and this field trip would not be possible for most school districts without the generous support of RaceTrac and the exhibition organizers. This will truly be one of those remarkable field trips that students will remember for the rest of their lives, and I urge our educators across GA to take advantage of this opportunity that has the potential to benefit thousands of kids across the state."

All Georgia schools are eligible to participate in the fuel program on a first-come, first-served basis, which will benefit up to 80,000 students. Educators interested in participating in the program and receiving the fuel subsidy may do so by calling 866-52GROUP or visiting http://www.goldengasoffer.com/.

Participation in this program could possibly alleviate moratoriums on school bus availability in some local communities for field trips to this exhibition. Schools receiving free admittance will be designated by the Georgia Department of Education.

"We take our commitment to the community and local youth very seriously," said Allison Moran, senior vice president of operations for RaceTrac. "As one of Georgia's leading gasoline retailers, and with the current economic climate threatening school field trips, this assistance program is the perfect opportunity for us to give back to the community by providing local children with access to an invaluable educational experience."

"Tutankhamun: The Golden King and the Great Pharaohs" is the second National Geographic exhibition dedicated to the remarkable treasures of King Tutankhamun and ancient Egyptian royalty. The first exhibition, "Tutankhamun and the Golden Age of the Pharaohs," has drawn 5 million visitors during its U.S. and London engagements, and has been visited by 250,000 schoolchildren since opening in June 2005.

"We are indeed grateful to businesses like RaceTrac that are rallying much-needed resources to make Tutankhamun accessible to schoolchildren in Georgia," said Bonnie Speed, director of the Michael C. Carlos Museum. "It takes an engaged community to understand the cultural and social significance of this exhibition -- its power to kindle the imagination, build bridges across cultures and provide an unparalleled educational experience. We hope that school systems across Georgia will take advantage of this once-in-a-lifetime opportunity."

"Tutankhamun: The Golden King and the Great Pharaohs" is organized by National Geographic, Arts and Exhibitions International (AEI) and AEG Exhibitions, with cooperation from the Supreme Council of Antiquities in Egypt. Northern Trust is the presenting sponsor, and American Airlines is the official airline of the exhibition.

"Seeing artifacts from King Tut and other Valley of the Kings tombs is truly a once-in-a-lifetime opportunity," said John Norman, president of Arts and Exhibitions International (AEI), one of the exhibition organizers. "We are committed to making every effort to ensure that this exhibition is accessible to students throughout the state, and RaceTrac's sponsorship helps make this possible."

ABOUT THE EXHIBITION

Premiering November 15, 2008 to May 25, 2009, at the Boisfeuillet Jones Atlanta Civic Center, "Tutankhamun: The Golden King and the Great Pharaohs" will feature striking objects from some of the most important rulers throughout 2,000 years of ancient Egyptian history, from the 4th Dynasty into the Late Period (about 2600 B.C. -- 660 B.C.). Derived from a variety of contexts, including temples and royal and private tombs, many of these artifacts have never before visited the United States.

The exhibition will highlight more than 50 treasures from Tutankhamun's tomb and more than 70 artifacts representing other pharaohs and notables, along with the latest scientific research about King Tut. The storyline will focus on the splendor of the Egyptian pharaohs, their function in the earthly and divine worlds, and what kingship meant to the Egyptian people.

Four galleries devoted to King Tut will correspond to the four rooms of his nearly intact tomb where the treasures were discovered by British explorer Howard Carter in 1922. Legendary artifacts from the antechamber, the annex, the treasury and the burial chamber will include Tutankhamun's golden sandals, jewelry, furniture, weaponry and statuary.

For more information about the exhibition, visit http://www.kingtut.org/.

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