Two of the four key sites designated for Automatic Dependent Surveillance-Broadcast (ADS-B) “critical services” have achieved initial operational capability (IOC).

Critical services IOC was declared at FAA’s Louisville, Ky., Terminal Radar Approach Control (Tracon) facility on Nov. 19, and at the Houston Air Route Traffic Control Center on Dec. 17, according to Vincent Capezzuto, FAA director of Surveillance and Broadcast Services and ADS-B program manager.

As required by the ADS-B ground system contract awarded to ITT Corp. in August 2007, critical services use GPS position data from properly equipped aircraft for presentation on air-traffic controller displays, allowing controllers to provide radar-like aircraft separations. “Essential services,” the uplink from the ground to aircraft of traffic and weather information, first entered service in November 2008 in southern Florida.

The Houston center provides air-traffic control over the Gulf of Mexico. IOC for ADS-B critical services there supports 5 nautical mile separation in non-radar airspace, benefiting petroleum industry support helicopters in particular. Some ADS-B ground stations are located on offshore oil platforms.

Petroleum Helicopters Inc. (PHI) is the first offshore operator to equip for ADS-B, and eight equipped helicopters flew IFR flight plans over the Gulf for the first time Dec. 17, Capezzuto told Avionics Magazine. “We’ve segregated the airspace,” he said. “If you can file IFR, you go up to 5,000 feet and you go direct to the (offshore) platform.”

Achieving critical services at the two remaining key sites -- the Philadelphia Tracon and Anchorage center, covering Juneau, Alaska -- will drive release of FAA’s ADS-B rulemaking, on track for release in April, Capezzuto said. The rule will establish performance requirements for avionics needed to operate in an ADS-B environment.

The rule was signed by FAA Administrator Randy Babbitt in early December and was being reviewed by the Department of Transportation. If DoT concurs with the rule, it will be sent for final review to the Office of Management and Budget.