Upgraded WAAS will provide more precise data

Upgraded WAAS will provide more precise data

FAA's enhanced landing navigation system has had problems, but review panel now says it will work better than expected


The Federal Aviation Administration and contractor Raytheon Co. will develop a three-year schedule by September to enhance the navigation capabilities of the Wide Area Augmentation System.

By 2003, WAAS will offer lateral and vertical guidance for landings when an aircraft is 400 feet above a runway and three-quarters of a mile away, said Hal Bell, the WAAS project team leader.

The system will allow small aircraft to land in poor visibility conditions at thousands of airports nationwide, Bell said.

Raytheon spokeswoman Blanche Necessary said the company is working on the details with FAA and is confident of delivering the system on schedule.

WAAS uses Global Positioning System satellites to provide precision navigation and landing guidance to aircraft at thousands of airports and airstrips that currently have no precision landing system.

It will augment the satellite data that FAA gets through GPS. The system uses 25 ground stations throughout the United States to receive signals from GPS satellites and determine if the signals contain errors. Data from the stations is collected at a master facility and uplinked to geostationary communications satellites that broadcast the corrected data to aircraft.

The system improves the accuracy and integrity of GPS signals and provides additional navigational information to aircraft.

Other benefits to civil aviation include more direct flight paths that airlines hope will save fuel and reduced maintenance costs associated with older ground-based navigation aids.

The program has run into mismanagement and cost overruns in the last few years.

Past problems

In 1999, FAA delayed WAAS implementation by more than a year as it refined the software for the Correction and Verification System, the final module that will monitor WAAS for errors and fix them (see story at www.gcn.com/archives/gcn/1999/February22/12a.htm).

The program got a boost in April when an independent panel said WAAS will work better than FAA had estimated.

Administered by the Institute for Defense Analyses in Alexandria, Va., the WAAS Independent Review Board met from August to December 2000 to review FAA's activities and offer advice regarding WAAS.

In its report, released in April, the board said the WAAS Integrity and Performance Panel, established in January 2000, should be extended through the initial commissioning of the system.

The panel's responsibilities should include system engineering, cost and schedule factors, the report said.

The biggest risk to the system is its dependence on only two communications satellites that have poor ranging accuracy and vulnerable links, the board noted. If one of the satellites fails, nearly half of the United States will lose coverage.

FAA should procure an additional satellite as an interim measure, the WAAS Independent Review Board recommended. As a long-term solution, it should plan on acquiring four communications satellites to ensure full coverage at all times.


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