Doug Strachan
President
SST: Strachan Strategic Thinking
1755 North Brown Rd., Suite 200
Lawrenceville, GA 30043

RNAV: Area Navigation

Situation

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In 1997, the City of Atlanta invested about $1 million in a NOMS (noise and operations monitoring system) to better address community concerns about perceived deviation from long used preferential flight paths termed NADTs, or noise abatement departure tracks.  NOMS was a geographic information system (GIS) that permitted analysis of aircraft noise and operational impacts relative to specific land parcels. NOMS components consisted of TAMIS, Total Airport Management Information Systems, 16 noise monitors that ringed the airport, and a direct connect to FAA radar data.

The NADTs were designed to keep aircraft departures over transportation corridors instead of over peoples' houses. Typical NADT width, five nautical miles (NM) from the departure end of a runway, was about 1.5 NM. In effect, that meant that people living in homes 0.75 NM on either side of the NADT had airplanes flying over them. Their conclusion? Pilots don't care about me; if they would try harder, they wouldn't fly over my house.

Task

First, develop a method to ensure that special causes of deviation from the extant NADT adherence process were eliminated. Second, find a way to reduce the standard deviation of flight tracks (the path on the ground of an airplane in flight) around the idealized NADT. In other words, squish the corridor so that airplanes would fly over the designated roadways and not over peoples' houses.

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Action

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Relative to the first action, i.e., improving adherence to the tracks with the vectored-by-controller process, analysis of pilot/controller conversations indicated that a paucity of controllers were deviating from authorized departure procedure language. Next, we discovered that the NADTs, used since 1972 at ATL, had never been codified on NACO (National Aeronautical Charting Organization) departure plates/charts, so we worked with them to codify the procedures so that pilots could reference them. Lastly, we distributed 10,000 copies of the brochure "NADTs: Noise Abatement Departure Tracks at Hartsfield Atlanta International Airport" to 10,000 pilots through airlines' chief pilots' offices.

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The second action required changing the existing vectoring-by-controller process. Controllers assigned wind-corrected NADT headings to pilots in five-degree increments, as airplane instrumentation was incapable of one-degree granularity. Pilots maintained these heading until being vectored again, unable to visually adhere to the NADT via point of reference. That is because once pilots lift off, they are pointed upward, and cannot see the transportation corridor that the NADT is designed to have them follow. There was no "line in the sky" for them to follow. We determined to give pilots that line in the sky.

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Very high frequency omnidirectional ranges (VORs), distance measuring equipment (DMEs), and even reverse instrument landing systems (ILSs) were deemed infeasible. Then we found a nascent technology called area navigation, or RNAV. RNAV largely eliminated the vectoring-by-controller process in favor of newer airplanes' flight management systems and GPS. The only issue was that the FAA had a moratorium on new RNAV standard instrument departures (SIDs), as the technology had failed at McCarran airport in Las Vegas.​

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While we could not implement new RNAV SIDs, nobody said we couldn't pull together FAA and airline experts and design the routes. So we did. While we could not implement new routes, nobody said that we could not flight test them. We did; they worked. While we could not implement the new routes, nobody prevented us from uploading them to the database from which pilots would one-day download them.

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Results

In June of 2005, after about 2.5 years of effort, RNAV SIDs went live at ATL. We took an NADT corridor that was about 1.5 NM wide, and squished it to less than 0.5 NM wide, delighting neighboring communities. Airlines' saved millions in fuel costs annually, due to having precise locations at which to expect turns towards destinations. Air traffic controllers' tactical work decreased, allowing them to focus on more strategic aspects of separating and sequencing airplanes. Because of the innovation at ATL relative to RNAV, we accelerated the pace at which the rest of the world has benefitted from this extremely beneficial technology.

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