US Federal Aviation Administration officials are considering whether alternatives such as the Local Area Augmentation System (LAAS) would be a better and cheaper way of achieving Category I approach capability than the troubled Wide Area Augmentation System (WAAS).
WAAS acceptance testing was halted in January because of excessive false alarms and stability issues. Carl McCullough, FAA director of communication, navigation and surveillance systems, says: "We created expectations...that we could not possibly achieve...the [WAAS] system was oversold and over-promised."
He acknowledges that the FAA does not know whether WAAS will deliver the planned Cat I capability. It will take at least nine months for a panel of experts to determine whether WAAS's full Cat I potential will be reached.
WAAS is designed to ensure the accuracy and integrity of global positioning system (GPS) signals. Its original cost estimate of $892 million has ballooned to $2.9 billion, while the commissioning date of July 1999 has slipped to 2002.
The FAA plans to implement in two years an initial level of WAAS service - lateral and vertical navigation (LNAV/VNAV) - providing approach guidance down to a 350ft (107m) decision height, compared with 200ft for Cat I. A proposal from WAAS prime contractor Raytheon to field the system initially with en route capability only has been rejected.
This would have delayed LNAV/VNAV implementation by up to three months, increased costs by $8 million and offered "marginal" operational benefits, the aviation agency says.
Raytheon has seven corrective actions to the stability problems, which are expected to be resolved by September, but there is no apparent solution to integrity monitoring problems, forcing the FAA to turn to outside experts for help.
Source: Flight International
