Narrative:

While on an ATC vector transitioning from armel VOR to the 10 DME fix for the river approach at dca, wash approach called VFR traffic at 2 O'clock and 5 mi, altitude unknown (this was the only advisory we received). The first officer and I looked intensively since visibility was good and we both thought we should be able to find him. The first officer looked down to change navigation frequencys and I reached up to check that the landing lights were all on (they were). I noticed movement in the windshield and an small aircraft (white with a red stripe) filled it. The aircraft was so close and at our altitude (5500') that I didn't bank thinking he would hit our wingtip. I pushed slightly forward on the wheel not wanting to raise my rudder into him with abrupt movement. I would estimate vertical sep at no more than 100' and he passed right over us. We came so close I actually heard his engine as we passed. We advised ATC of a near miss and continued a normal approach and landing at dca. I don't think the pilot ever saw us! I turned to give his position to ATC and he was still on course and altitude. I believe he was sightseeing just outside of the TCA and all eyes were on downtown washington. This is a perfect case for mandatory mode C requirements in small aircraft. Had ATC reported his altitude to me this near miss would not have happened. Supplemental information from acn 83316: at the time we were in a gradual descent for our approach into dca. No substantial evasive action was taken, other than a slight lowering of the nose, as the captain felt that to bank the aircraft or make too radical a nose down pitch might increase the chance of a collision due to the proximity of the other aircraft.

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Original NASA ASRS Text

Title: CLOSE PROX ACR-MLG GA-SMA AT THE EDGE OF DCA TCA.

Narrative: WHILE ON AN ATC VECTOR TRANSITIONING FROM ARMEL VOR TO THE 10 DME FIX FOR THE RIVER APCH AT DCA, WASH APCH CALLED VFR TFC AT 2 O'CLOCK AND 5 MI, ALT UNKNOWN (THIS WAS THE ONLY ADVISORY WE RECEIVED). THE F/O AND I LOOKED INTENSIVELY SINCE VIS WAS GOOD AND WE BOTH THOUGHT WE SHOULD BE ABLE TO FIND HIM. THE F/O LOOKED DOWN TO CHANGE NAV FREQS AND I REACHED UP TO CHK THAT THE LNDG LIGHTS WERE ALL ON (THEY WERE). I NOTICED MOVEMENT IN THE WINDSHIELD AND AN SMA (WHITE WITH A RED STRIPE) FILLED IT. THE ACFT WAS SO CLOSE AND AT OUR ALT (5500') THAT I DIDN'T BANK THINKING HE WOULD HIT OUR WINGTIP. I PUSHED SLIGHTLY FORWARD ON THE WHEEL NOT WANTING TO RAISE MY RUDDER INTO HIM WITH ABRUPT MOVEMENT. I WOULD ESTIMATE VERT SEP AT NO MORE THAN 100' AND HE PASSED RIGHT OVER US. WE CAME SO CLOSE I ACTUALLY HEARD HIS ENG AS WE PASSED. WE ADVISED ATC OF A NEAR MISS AND CONTINUED A NORMAL APCH AND LNDG AT DCA. I DON'T THINK THE PLT EVER SAW US! I TURNED TO GIVE HIS POS TO ATC AND HE WAS STILL ON COURSE AND ALT. I BELIEVE HE WAS SIGHTSEEING JUST OUTSIDE OF THE TCA AND ALL EYES WERE ON DOWNTOWN WASHINGTON. THIS IS A PERFECT CASE FOR MANDATORY MODE C REQUIREMENTS IN SMA. HAD ATC RPTED HIS ALT TO ME THIS NEAR MISS WOULD NOT HAVE HAPPENED. SUPPLEMENTAL INFO FROM ACN 83316: AT THE TIME WE WERE IN A GRADUAL DSCNT FOR OUR APCH INTO DCA. NO SUBSTANTIAL EVASIVE ACTION WAS TAKEN, OTHER THAN A SLIGHT LOWERING OF THE NOSE, AS THE CAPT FELT THAT TO BANK THE ACFT OR MAKE TOO RADICAL A NOSE DOWN PITCH MIGHT INCREASE THE CHANCE OF A COLLISION DUE TO THE PROX OF THE OTHER ACFT.

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.