Narrative:

We were downwind (left hand traffic) for XR44 (miami seaplane base) and operating in a mia VFR corridor. Our flight path was wbound just past midfield when the first officer took the controls from me and made about a 45 degree bank left climbing turn. This action was a result of him seeing, just a few seconds before, a high wing single engine small aircraft southbound and below us about 50', and apparently not talking to mia. The first officer said he made the climbing left turn because at the moment he saw the small aircraft, the small aircraft pilot must have seen us and pulled his aircraft up towards us and apparently went over us. This information was told to me by my first officer. I did not see the small aircraft because he was approaching from the first officer's side and below us. My first sighting of the aircraft was when we turned on final approach and the small aircraft was still southbound towards biscayne bay area at about 800'. I believe the problem was caused by private aircraft operating near a busy airport. This area is in the downtown area of miami and small aircraft tend to get lost from visual contact due to ground clutter.

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Original NASA ASRS Text

Title: NMAC ACR-SMT SEAPLANE AND SMA.

Narrative: WE WERE DOWNWIND (LEFT HAND TFC) FOR XR44 (MIAMI SEAPLANE BASE) AND OPERATING IN A MIA VFR CORRIDOR. OUR FLT PATH WAS WBOUND JUST PAST MIDFIELD WHEN THE F/O TOOK THE CONTROLS FROM ME AND MADE ABOUT A 45 DEG BANK LEFT CLBING TURN. THIS ACTION WAS A RESULT OF HIM SEEING, JUST A FEW SECS BEFORE, A HIGH WING SINGLE ENG SMA SBND AND BELOW US ABOUT 50', AND APPARENTLY NOT TALKING TO MIA. THE F/O SAID HE MADE THE CLBING LEFT TURN BECAUSE AT THE MOMENT HE SAW THE SMA, THE SMA PLT MUST HAVE SEEN US AND PULLED HIS ACFT UP TOWARDS US AND APPARENTLY WENT OVER US. THIS INFO WAS TOLD TO ME BY MY F/O. I DID NOT SEE THE SMA BECAUSE HE WAS APCHING FROM THE F/O'S SIDE AND BELOW US. MY FIRST SIGHTING OF THE ACFT WAS WHEN WE TURNED ON FINAL APCH AND THE SMA WAS STILL SBND TOWARDS BISCAYNE BAY AREA AT ABOUT 800'. I BELIEVE THE PROB WAS CAUSED BY PVT ACFT OPERATING NEAR A BUSY ARPT. THIS AREA IS IN THE DOWNTOWN AREA OF MIAMI AND SMALL ACFT TEND TO GET LOST FROM VISUAL CONTACT DUE TO GND CLUTTER.

Data retrieved from NASA's ASRS site as of August 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.