FAA Safety Alert - ADS-B

Purpose: This SAFO informs personnel involved with ground testing of aircraft Air Traffic Control (ATC) transponders and ADS-B OUT equipment of the importance of adhering to proper test procedures and the hazards associated with improper testing.

Background: The Federal Aviation Administration (FAA) has received reports of transponder and ADS- B OUT system ground test events in which information, including simulated altitude, was transmitted from the test aircraft and received by aircraft inflight. In at least one instance, an ADS-B OUT system ground test created a false airborne target that generated a Traffic Alert and Collison Avoidance System II (TCAS II) Resolution Advisory (RA) on a Boeing 737 aircraft on approach. Pilot reaction to this RA required unnecessary maneuvering in congested airspace and initiated ATC re-sequencing actions that affected multiple aircraft and negatively impacted operations in the area for about 30 minutes. 

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