Raytheon and US Federal Aviation Administration officials have held the first of a series of meetings to determine the impact of problems uncovered during acceptance testing of the Wide Area Augmentation System (WAAS).

A 60-day stability test of the key satellite-based navigation system, intended to improve the accuracy, availability and integrity of the global positioning system (GPS), was halted because an excessive false-alarm rate generated by the WAAS integrity monitor reduced availability of the GPS signal.

New FAA director of communication, navigation and surveillance systems Carl McCollough says it is "unlikely" the agency will meet its September deadline for deployment of the first phase of WAAS. "It's hard to tell by how far we will miss," he says. "It depends on the level of service the customer will expect. We will see what we can deliver and what is acceptable."

Although terminated prematurely, the stability test showed that WAAS exceeds its accuracy goal by a factor of two to three, says McCollough. The system achieved an accuracy of 2.5-3m (8-10ft), compared with the specification requirement of 7.6m, he says. "Performance measured by accuracy is very good, but we are not yet there on the safety side," he adds.

Testifying before Congress, FAA Administrator Jane Garvey last week said that the agency will not certificate WAAS until it can ensure the system is safe. McCollough says the FAA is aiming for a probability of a hazardously misleading signal of one in 10 million (10-7) - the same criterion using in certificating avionics, "but we have never certificated a system like this before".

Meanwhile, the FAA is facing budget problems with WAAS. Congress has cut its funding by a quarter in fiscal year 2000, to $82 million, and barred work on the system beyond the Phase 1 initial operational capability. This is to give the FAA time to reassess justification for WAAS.

Source: Flight International