Gulf Outage Exposes ADS-B Oversight Vulnerability

 - August 29, 2011, 5:05 AM

The loss of service from automatic dependent surveillance-broadcast (ADS-B) stations in the Gulf of Mexico last summer exposed the risk inherent in the FAA monitoring a contractor-owned system, according to the U.S. Department of Transportation.

The ADS-B network in the Gulf experienced an outage of more than 11 hours on Aug. 6, 2010, requiring air traffic controllers to separate ADS-B equipped aircraft in nonradar airspace manually. The FAA system designed to monitor the ground stations that send surveillance data to the network, called the Surveillance and Broadcast Service (SBS), failed to work as intended and proved unreliable, states an audit report by the DoT Inspector General.

Issued August 4, the IG report cites the Gulf outage to support its larger argument that by ceding operation of the ADS-B system to a contractor, the FAA risks “losing long-term visibility into system performance” not only of ADS-B, but of other systems underpinning the Next Generation Air Transportation System. Under terms of the ADS-B contract awarded to ITT in August 2007, the FAA owns the surveillance data generated by the system, and the system design and configuration. ITT owns the ground infrastructure of radio stations that transmits surveillance data to FAA ATC facilities. There will be 794 ground stations installed nationwide by 2013.

The FAA revised its certification procedures in September 2007 to clarify that only FAA-owned or -maintained systems must be certified, the IG said. The agency developed the SBS to monitor the operation of equipment at individual radio sites. It planned to deploy some 20 monitors, but because of cost scaled that back to two systems, located at the FAA Technical Center in Atlantic City, N.J., and Aeronautical Center in Oklahoma City.

If the system works as planned, ADS-B in the Gulf will eventually benefit hundreds of oil industry transport helicopters that adhere to an inefficient grid pattern when flying through nonradar airspace to reach offshore platforms. The ADS-B network consists of 21 radio stations–nine located at terrestrial sites and 12 on offshore platforms. Petroleum Helicopters was the first operator to equip for ADS-B, beginning IFR flights over the Gulf in December 2009.

At the time of the outage, ITT was operating a single network hub without a back-up capability, the IG said. “Surveillance data transmitted by ITT’s ground system through the hub stopped reaching FAA control centers. At the same time, the SBS monitors stopped receiving ground equipment status information because this information also flows through the hub and not directly from ITT’s ground system components.” The FAA and ITT have since implemented a remediation plan to improve SBS reliability.

ITT declined to comment on the IG report. At the Paris Air Show in June, John Kefaliotis, ITT vice president of Next Generation Transportation Systems, asserted the ADS-B program is an example of a successful public-private partnership that “delivers very substantial benefits.” The company has met all milestones in the four years since winning the contract from the FAA, having invested $200 million in the effort, he said.