General Discussion

A lot of people asking what the helo was doing there. USCG helo pilot here who's flown that route
a thousand times: DC has a whole network of helo routes and zones designed to organize helo traffic and route it under and around commercial traffic. Route 4 goes right down the east side of the Potomac, max altitude of 200 ft. It is not uncommon for helos to be flying under landing traffic once visual
separation is established and with correct altitudes maintained. From the ADSB data, it looks like the helo was southbound on Route 4, and the airliner was on final to rwy 33. Here's one plausible scenario... just one that fits the facts we know right now, could be totally wrong: Landing on 33 is not as common as landing on wy 1. Airliners are often not cleared/switched for RWY 33 until just a few miles south of the Wilson Bridge. Let's say the H60 is southbound and is told to maintain visual separation with the landing CRJ. The 60 crew may not have caught that the CRJ in question was landing 33, which is less common. They look south and see lights of the next aircraft lined up for RWY 01, and they report "traffic in sight, will maintain visual separation." Then they cruise south, looking south. Maybe the CRJ is a little low on their approach or the H60 is accidentally a little high on their route and fails to see the CRJ approaching from their 10 o'clock. The CRJ is focused on DCA which is surrounded by a sea of lights in the metro area. They don't notice one small set of lights out of place at their 1-2 o'clock as they focus on the runway. The controller believes the helo will maintain visual separation so