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WAAS summit consensus: System needed and should proceedWAAS summit consensus: System needed and should proceed

WAAS summit consensus: System needed and should proceed
New 'LNAV/VNAV' approaches slated

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FAA Deputy Administrator Monte Belger, FAA Administrator Jane Garvey, AOPA President Boyer, FAA Chief of Staff Carl Burleson, and Dennis Roberts, AOPA vice president of Government and Technical Affairs at the WAAS Summit Meeting.

The GPS Wide Area Augmentation System (WAAS) is needed, and the FAA should continue developing the program. That was the consensus of top-level aviation industry officials at an intense "WAAS Summit Meeting" March 15 in Washington.

Following a series of program delays, technical setbacks, and increasing costs, AOPA and the Air Transport Association called for the meeting of top-level FAA officials and their WAAS contractors, plus industry, airline, and general aviation user groups for answers on user needs, WAAS benefits, and system delivery schedules and costs.

(WAAS enhances the accuracy, availability, and integrity of GPS signals for primary en route and terminal navigation and to provide vertical guidance for instrument approaches.)

During the unusually candid meeting, senior FAA officials said it was "painful to admit" the program had not yet delivered as promised. The FAA contingent included FAA Administrator Jane Garvey, Deputy Administrator Monte Belger, and senior officials responsible for WAAS development and certification.

New 'LNAV/VNAV' capability promised by 2002

The FAA promised that WAAS would deliver a new RNAV (area navigation) approach capability called LNAV/VNAV (lateral and vertical navigation) to the majority of the nation's airports by 2002.

LNAV/VNAV would permit approach minimums including a 350-foot decision altitude and one-mile visibility requirement at most airports, without additional lighting systems or other expensive airport improvements.

"That would be a huge benefit and a tremendous safety advantage for general aviation," said AOPA President Phil Boyer, who chaired the summit meeting. "For GA, what we really want to do is get below the clouds. That's a good, safe approach."

"We'd take 350 feet and one mile in a heartbeat," said Bob Blouin of the National Business Aviation Association. Regional Airline Association President Walt Coleman pointed out that more airlines are expanding service with small "regional jets" (RJs), but the majority of airports they will serve do not have instrument approaches with vertical guidance.

"Our members are buying RJs, too," said the Air Transport Association's Bob Frenzel, "and they will benefit from WAAS."

"Aviation is growing, but God isn't making any more airspace and we're not building many more airports," said Steve Alterman of the Cargo Airline Association. "We need to manage the airspace better, and WAAS is the key."

WAAS is also key to other programs, including runway incursion prevention, Safe Flight 21, and Free Flight. WAAS-guided approaches and departures can help with noise abatement as well.

Independent panel says WAAS can deliver

But can the FAA and its WAAS contractor, Raytheon, really deliver on this promise?

WAAS Summit Meeting discussions reported that an independent review panel of experts from Stanford University, the Jet Propulsion Laboratory, MITRE Corporation, and Ohio University is now working with the FAA and Raytheon to identify cost-effective and expedient solutions to remaining WAAS issues.

This so-called WAAS Integrity Performance Panel (WIPP) has already concluded that WAAS can deliver LNAV/VNAV services. WIPP panel member Per Enge of Stanford University called the WAAS performance solutions "crisp."

The answers aren't so clear for RNAV approaches to lower minimums.

WAAS originally promised ILS-like Category I approaches to 200-foot decision altitude/1/2-mile visibility at many airports with the appropriate lighting systems, runway markings, etc. In testing so far, system accuracy has consistently exceeded Category I standards.

However, system integrity hasn't yet met certification standards. (Integrity describes the system's ability to detect a problem with the navigation signal and warn the pilot quickly.)

WIPP experts believe WAAS can eventually provide guidance down to Category I minimums. They are now scheduled to report by December 2000 on how and when WAAS can meet that standard, a satellite navigation service to be called "GLS."

New approach definitions

Because old definitions of "precision" and "nonprecision" approaches don't fit the new world of satellite navigation, the FAA has developed new terms and standards for instrument approaches grouped under the general category of RNAV (area navigation). New RNAV instrument approach charts, already appearing in approach plate books, include:

  • LNAV—A "nonprecision" approach (no vertical guidance) with a minimum descent altitude (MDA) of 250 feet above obstacles along the flight path. At many airports, LNAV approaches will have lower minimums than existing VOR or NDB approaches. LNAV approaches can be conducted today with approach-certified (TSO-129) GPS receivers.
  • LNAV/VNAV—A vertically guided approach with a decision altitude down to 350 feet above the runway touchdown point (HAT). Requires a WAAS-certified receiver (or certain flight management systems with barometric VNAV). Visibility requirements are generally one mile at airports without approach lighting systems.
  • GLS (Global Navigation Satellite System Landing System)—A vertically guided approach using an approach-certified WAAS receiver. Will have lower decision altitudes and visibility requirements than LNAV/VNAV. GLS PA will have the have the lowest minimums (200 feet and 1/2-mile visibility). "PA" indicates the availability of a precision approach runway, which includes approach lights, runway lights, runway markings, parallel taxiways, etc.

(For more information, see "Hello WAAS" (October 1999 Pilot).

The 355,000-member Aircraft Owners and Pilots Association is the world's largest civil aviation organization. More than one half of the nation's pilots are AOPA members.


March 23, 2000

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