Virginia Tech recently has conducted a study for the U.S. Federal Aviation Administration (FAA) that says fuel savings and a reduction in greenhouse emissions are within reach if space separation rules are changed. Antonio Trani, director of Virginia Tech's Air Transportation Systems Laboratory and civil and environmental engineering professor, led the study.

"If the lateral separation between the aircraft can be reduced, they can be spaced closer and remain more in line with their optimum flight paths,” Trani says. “Overall, this would produce fuel economy as most aircraft save fuel at higher cruise altitudes."

(The FAA defines a large height deviation as any vertical departure of 300 feet or more from the expected flight level.)

The researchers called their new computer model the North Atlantic Systems Analysis Model (NATSAM III). After they demonstrated its viability, one result was the FAA's decision to extend the study to the Pacific Ocean aviation operations.

Areas of research included making recommendations on restricted cruise altitudes for aircraft crossing the North Atlantic oceanic airspace where commercial traffic is the majority of crossings. Canada, Denmark, France, Iceland, Ireland, Norway, Portugal, the United Kingdom and the United States all use the space. In particular, the research says that large separation standards are in place. These limit the proximity of aircraft to each other, and result in greater fuel usage. Trani and his colleagues developed a computer model that shows that aircraft can fly at a spacing of five minutes apart, half of what is currently mandated.

According to him, the study gathered information for 44 major airlines that represent 81.6% of the North Atlantic Systems operations and 88.2% of commercial operations.

Cost data to upgrade aircraft with communication equipment included more than 40 participants from the aircraft and avionics manufacturers, commercial airlines, International General Aviation representatives and all of the North Atlantic Systems Air Navigation Service providers. Most of the airspace involved is out of range of very high frequency radio and radar, meaning that more than 800 airframes would need some retrofit, totaling an estimated $464 million in 2010 dollars.

The study estimates that annual fuel benefits from the suggested changes would be $10 million at five-minute intervals between planes. At two-minute intervals, the savings could be more than $35 million.

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