Convective weather systems, i.e., thunderstorms, are the leading cause of flight delay in U.S. airspace. Airline dispatchers must file their flight plans 1 to 2 hours before takeoff, and are often required to incorporate large buffers to forecast weather. Weather changes as flights progress, and airline dispatchers, Federal Aviation Administration (FAA) traffic managers, and air traffic controllers are especially busy during weather events. Workable opportunities for more efficient routes around bad weather are often missed, and automation does not exist to help operators determine when weather avoidance routes have become stale and could be updated to reduce delay.

Sample DWR route correction implemented by American Airlines.
The DWR innovation is a ground-based computer automation system that analyzes in-flight aircraft in en route airspace, and automatically finds flights where simple corrections to flight plan routes could save significant flight time and fuel by flying more efficient routes around convective weather. Strong collaborations with the airlines and the FAA have enabled NASA to demonstrate and validate the DWR concept and prototype in real-world air traffic operations.

The DWR automation continuously and automatically analyzes in-flight aircraft in en route airspaces and identifies flights where a simple route correction could save significant flying time (5 or more minutes, wind-corrected) while avoiding convective weather and considering other factors important to air traffic operations such as traffic congestion, traffic conflicts, restricted airspace, and FAA routing restrictions. Primary inputs to the DWR system include local en route center surveillance radar and flight plan data, national surveillance and flight plan data for traffic congestion calculations, and convective weather forecast model data, which includes a 2-hour forecast with 5-minute look-ahead time steps, wind forecast data, status updates on restricted (special use) airspace and FAA routing restrictions, and a database of aircraft performance models for climb and descent trajectory modeling. Update rates on the DWR inputs vary from every 12 seconds for en route radar data to every 5 minutes for convective weather updates, to every hour for wind forecast data.

The DWR automation runs in the background in real time, and flights for which a route correction has been identified are posted to a flight list ordered by potential flying time savings. Interactive point-andclick user interface functions enable users to visualize proposed route corrections and modify them if necessary while assessing in real time the impact of route changes on flying time, airspace sector congestion, traffic conflicts, restricted airspace, and routing restrictions. Laboratory test results show a potential savings of about 100,000 flying minutes for 15,000 flights in the Fort Worth Center airspace in 2013.

An operational trial of DWR has been under way at the American Airlines (AA) Integrated Operations Center (IOC) in Fort Worth, TX since July 2012. The DWR software runs at NASA’s North Texas Research Station (NTX), and a DWR user display (filtered to alert AA flights only) is located on the AA IOC operations floor at a position called the Air Traffic Control Desk. When a route correction for a new flight is identified and first posted to the DWR flight list, an audible tone alerts the AA air traffic control (ATC) coordinators (primary DWR users) to the presence of a proposed route correction for a new AA flight. The audible tone (that of an old fashioned cash register) is an important element of the trial operating concept as it informs AA users — who are busy with other tasks — that a new flight has been posted to the DWR flight list. The ATC coordinator reviews the proposed route correction and modifies it if necessary. If the ATC coordinator and the flight dispatcher in charge of the flight both consider the route change acceptable, beneficial, and safe, the dispatcher sends a message to the flight crew (using the Aircraft Communication Addressing and Reporting System, or ACARS) suggesting the route change for time and fuel savings. The flight crew evaluates the proposed route change, and if they agree, request the route change from FAA air traffic control using normal procedures. Feedback from AA users has been very favorable. During the 2+ year trial period, 64% of the route corrections proposed by DWR have been rated acceptable by AA ATC coordinators and dispatchers. The most common reasons for AA users to modify, or sometimes reject, a DWR advisory is when the proposed route correction takes the flight too close to weather or too close to merging arrival traffic preparing for descent to the Dallas or Houston airports. Work is ongoing to refine the algorithms to address these issues.

Test results for the period 7/31/12 to 9/10/14 indicate an estimated actual savings of 3,729 minutes for 575 AA flights, or about 6.5 minutes per flight on average. On a recent September 2014 “badweather” day in North Texas, AA used DWR to save about 130 minutes flying time for 12 AA flights, including 31 minutes savings [about 3,600 lb (≈1,632 kg) of fuel] for an MD82 aircraft flying from Dallas to New Orleans (see figure), and 26 minutes savings [about 6,280 lb (≈2,850 kg) of fuel] for a B777 aircraft flying from Dallas to Buenos Aires.

Several aerospace companies and other airlines have expressed interest in the DWR concept and software. The DWR software has been licensed (non-exclusively) to one large aerospace company and a license for another at the time of this reporting is pending.

This work was done by Dave McNally, Kapil Sheth, and Chester Gong of Ames Research Center. NASA invites companies to inquire about partnering opportunities and licensing this patent-pending technology. Contact the Ames Technology Partnerships Office at 1-855-627-2249 or This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to ARC-16846-1.

NASA Tech Briefs Magazine

This article first appeared in the November, 2015 issue of NASA Tech Briefs Magazine.

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