Narrative:

Maneuvering in good VMC for landing on runway 21 at dca (cleared for visibility approach, monitoring tower frequency for landing clearance). Tower advised of helicopter traffic below and ahead. This traffic was spotted flying southwest where anacostia river meets potomac. No conflict, initially. The helicopter, a military type, then turned northwest up the potomac river. This now became an immediately increasing traffic conflict. Converging flight paths. I asked tower to provide sep, hoping he would stop, slow or turn the helicopter. He responded with, 'maintain visibility sep.' maneuvering in close for a STOL landing allows for very little leeway from the desired flight path. A go around from this position is also dangerous. There was no time to communicate this to tower and the helicopter was on a different frequency. I continued and landed very cautiously when I realized we would miss traffic. However, we only missed by approximately 300'. I feel that ATC (tower) ignored its basic obligation of providing sep. The helicopter could have easily been slowed, stopped or turned as a means of avoiding an impending collision. Tower certainly would have been aware of both aircraft's flight paths. I hope they (tower) do not think 200-300' is a safe amount of traffic sep. This helicopter conflict, and poor ATC sep of it, at dca is an ongoing problem. Here is an accident waiting to happen.

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Original NASA ASRS Text

Title: ALLEGED TRAFFIC CONFLICT BETWEEN COMMUTER AND MIL HELICOPTER.

Narrative: MANEUVERING IN GOOD VMC FOR LNDG ON RWY 21 AT DCA (CLRED FOR VIS APCH, MONITORING TWR FREQ FOR LNDG CLRNC). TWR ADVISED OF HELI TFC BELOW AND AHEAD. THIS TFC WAS SPOTTED FLYING SW WHERE ANACOSTIA RIVER MEETS POTOMAC. NO CONFLICT, INITIALLY. THE HELI, A MIL TYPE, THEN TURNED NW UP THE POTOMAC RIVER. THIS NOW BECAME AN IMMEDIATELY INCREASING TFC CONFLICT. CONVERGING FLT PATHS. I ASKED TWR TO PROVIDE SEP, HOPING HE WOULD STOP, SLOW OR TURN THE HELI. HE RESPONDED WITH, 'MAINTAIN VIS SEP.' MANEUVERING IN CLOSE FOR A STOL LNDG ALLOWS FOR VERY LITTLE LEEWAY FROM THE DESIRED FLT PATH. A GAR FROM THIS POS IS ALSO DANGEROUS. THERE WAS NO TIME TO COMMUNICATE THIS TO TWR AND THE HELI WAS ON A DIFFERENT FREQ. I CONTINUED AND LANDED VERY CAUTIOUSLY WHEN I REALIZED WE WOULD MISS TFC. HOWEVER, WE ONLY MISSED BY APPROX 300'. I FEEL THAT ATC (TWR) IGNORED ITS BASIC OBLIGATION OF PROVIDING SEP. THE HELI COULD HAVE EASILY BEEN SLOWED, STOPPED OR TURNED AS A MEANS OF AVOIDING AN IMPENDING COLLISION. TWR CERTAINLY WOULD HAVE BEEN AWARE OF BOTH ACFT'S FLT PATHS. I HOPE THEY (TWR) DO NOT THINK 200-300' IS A SAFE AMOUNT OF TFC SEP. THIS HELI CONFLICT, AND POOR ATC SEP OF IT, AT DCA IS AN ONGOING PROB. HERE IS AN ACCIDENT WAITING TO HAPPEN.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.