TL;DR: FAA's fault for allowing those helicopter routes in close proximity to DCA flight path.
For those that want to read the full probable cause statement.
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We determined that the probable cause of this accident was the FAA’s
placement of a helicopter route in close proximity to a runway approach path; their
failure to regularly review and evaluate helicopter routes and available data, and their
failure to act on recommendations to mitigate the risk of a midair collision near
Ronald Reagan Washington National Airport; as well as the air traffic system’s
overreliance on visual separation in order to promote efficient traffic flow without
consideration for the limitations of the see-and-avoid concept. Also causal was the
lack of effective pilot-applied visual separation by the helicopter crew, which resulted
in a midair collision. Additional causal factors were the tower team’s loss of situation
awareness and degraded performance due to the high workload of the combined
helicopter and local control positions and the absence of a risk assessment process to
identify and mitigate real-time operational risk factors, which resulted in
misprioritization of duties, inadequate traffic advisories, and the lack of safety alerts to
both flight crews. Also causal was the Army’s failure to ensure pilots were aware of
the effects of error tolerances on barometric altimeters in their helicopters, which
resulted in the crew flying above the maximum published helicopter route altitude.
Contributing factors included:
• the limitations of the traffic awareness and collision alerting systems on
both aircraft, which precluded effective alerting of the impending collision
to the flight crews
• an unsustainable airport arrival rate, increasing traffic volume with a
changing fleet mix, and airline scheduling practices at DCA, which regularly
strained the DCA ATCT workforce and degraded safety over time;
• the Army’s lack of a fully implemented safety management system, which
should have identified and addressed hazards associated with altitude
exceedances on the Washington, DC, helicopter routes;
• the FAA’s failure across multiple organizations to implement previous NTSB
recommendations, including ADS-B In, and to follow and fully integrate its
established safety management system, which should have led to several
organizational and operational changes based on previously identified risks
that were known to management; and
• the absence of effective data sharing and analysis among the FAA, aircraft
operators, and other relevant organizations.
