On the evening of Tuesday, 24 March a US Army Blackhawk helicopter crossed in front of a United Airlines 737 on approach to Santa Ana John Wayne Airport (SNA) in California. The proximity of the helicopter and 737-800 generated a Traffic Collision Avoidance System Resolution Advisory (TCAS RA) for the United crew.
United flight UA589 was on approach to Santa Ana descending through 2,000 feet when the US Army Black Hawk helicopter crossed in front of the 737 at an altitude of 1,425 feet. At 03:40:35 UTC the two aircraft were at their closest point, separated by 525 feet vertically and 1,422 feet laterally.
United 589 arrested its descent in response the TCAS Resolution Advisory then continued its descent into Santa Ana landing safely approximately 3 minutes later.
FAA opens an investigation
The FAA announced Thursday, 26 March that it was beginning an investigation into the incident, “including whether a new measure to suspend the use of visual separation between airplanes and helicopters was applied.”
The reference to a “new measure” relates to the FAA’s recent rule change banning the use of visual separation between helicopter and fixed-wing traffic near the country’s busiest airports. The new rule mandates the use of radar separation to actively separate the aircraft instead of allowing to helicopter traffic to visually confirm they are free of conflict.
Downloadable data
The two CSV files available for download are granular data excerpts from the relevant portion of each flight. In the data, TCAS status = 3 denotes the presence of a Resolution Advisory.
Aircraft information
United flight UA589 from San Francisco to Santa Ana was operated by a Boeing 737-800 powered by two CFM56 engines. The US Army UH-60M Black Hawk helicopter is operated by crews from the California Air National Guard.
