Navigation system promises to improve approach guidance down to as low as 250ft

UPS Aviation Technologies (UPSAT) has received the first certification for a wide-area augmentation system (WAAS) GPS satellite navigation receiver. The Raytheon-developed WAAS is scheduled to become operational over continental USA in 2003, initially providing lateral and vertical navigation to minima as low as 250ft (75m).

The US Federal Aviation Administration has granted Technical Standard Order C145a approval to the WAAS GPS receiver used in UPS AT's AT9000-series link and display processing unit (LDPU), the heart of the firm's automatic dependent surveillance-broadcast (ADS-B) system for commercial transport aircraft.

The WAAS "engine" can track 15 GPSs simultaneously with up to three geostationary satellites broadcasting the WAAS signal, which improves GPS accuracy from 100m to about 7m. Raytheon completed a 60-day stability test of the system in September, ahead of FAA acceptance of the WAAS in February.

At WAAS commissioning, expected later this year, the system is expected to support approaches with vertical guidance down to minima ranging from about 350ft and 1nm (1.8km) visibility, down to as low as 250ft in optimum terrain. The capability will cover about 50% of the continental USA.

Later phases will expand approach capability throughout mainland USA and into Alaska, Canada and Mexico. Plans call for minima to be lowered until a WAAS approach "is essentially the same" as a Category 1 instrument landing system approach, says Raytheon.WAAS also supports required navigation performance (RNP) operations, says Raytheon, providing a precision navigation capability down to RNP 0.02 (an accuracy of 0.02nm). The FAA is progressing with plans to establish RNP airspace and procedures over the USA within the next year.

UPS AT's ADS-B LDPU works with the company's AT7000 Mode-S datalink transponder and AT2000 cockpit traffic information display. The display is being installed in more than 100 Boeing 757s and 767s operated by UPS Airlines, while the transponder has been certificated in a UPS 757.

Source: Flight International