Narrative:

We were climbing through approximately 15500-16000 ft, 25 mi southeast of the hopewell VOR (en route from norfolk to newark) when the captain observed a white small transport passing directly underneath us with about 200 ft clearance. We were cleared to climb to FL210. No traffic was reported to us. We were heading 330 degrees. The small transport appeared to be nebound. He was observed at our 9 O'clock position and went to our 4 O'clock position as he passed by. We were in his 12 O'clock position at the time of the conflict. Our speed was 300 KIAS. We were just entering the base of a haze layer which reduced visibility somewhat. When we told ATC (ZDC) about the conflict, he told us he had a primary target only that was now at our 4 O'clock and 3 mi. About 1 min later, ATC reported to us that the small transport had turned on his transponder, and his altitude readout was 15400 ft. We took no evasive action because the captain did not see the traffic until a split second before he passed under us. The first officer never observed the traffic. Our aircraft was not TCASII equipped. TCASII would not have helped in this case, since the small transport did not have his transponder turned on. My only suggestion is that xponders should be required on all aircraft above 10000 ft MSL. At the speeds we operate above 10000 ft, the 'see and avoid' concept might sound good, but it is not a realistic solution to collision avoidance. Had the small transport been operating his transponder, ATC would have alerted us to the conflict, even without TCASII.

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Original NASA ASRS Text

Title: MLG HAS NMAC WITH SMT AT 15500 FT.

Narrative: WE WERE CLBING THROUGH APPROX 15500-16000 FT, 25 MI SE OF THE HOPEWELL VOR (ENRTE FROM NORFOLK TO NEWARK) WHEN THE CAPT OBSERVED A WHITE SMT PASSING DIRECTLY UNDERNEATH US WITH ABOUT 200 FT CLRNC. WE WERE CLRED TO CLB TO FL210. NO TFC WAS RPTED TO US. WE WERE HDG 330 DEGS. THE SMT APPEARED TO BE NEBOUND. HE WAS OBSERVED AT OUR 9 O'CLOCK POS AND WENT TO OUR 4 O'CLOCK POS AS HE PASSED BY. WE WERE IN HIS 12 O'CLOCK POS AT THE TIME OF THE CONFLICT. OUR SPD WAS 300 KIAS. WE WERE JUST ENTERING THE BASE OF A HAZE LAYER WHICH REDUCED VISIBILITY SOMEWHAT. WHEN WE TOLD ATC (ZDC) ABOUT THE CONFLICT, HE TOLD US HE HAD A PRIMARY TARGET ONLY THAT WAS NOW AT OUR 4 O'CLOCK AND 3 MI. ABOUT 1 MIN LATER, ATC RPTED TO US THAT THE SMT HAD TURNED ON HIS XPONDER, AND HIS ALT READOUT WAS 15400 FT. WE TOOK NO EVASIVE ACTION BECAUSE THE CAPT DID NOT SEE THE TFC UNTIL A SPLIT SECOND BEFORE HE PASSED UNDER US. THE FO NEVER OBSERVED THE TFC. OUR ACFT WAS NOT TCASII EQUIPPED. TCASII WOULD NOT HAVE HELPED IN THIS CASE, SINCE THE SMT DID NOT HAVE HIS XPONDER TURNED ON. MY ONLY SUGGESTION IS THAT XPONDERS SHOULD BE REQUIRED ON ALL ACFT ABOVE 10000 FT MSL. AT THE SPDS WE OPERATE ABOVE 10000 FT, THE 'SEE AND AVOID' CONCEPT MIGHT SOUND GOOD, BUT IT IS NOT A REALISTIC SOLUTION TO COLLISION AVOIDANCE. HAD THE SMT BEEN OPERATING HIS XPONDER, ATC WOULD HAVE ALERTED US TO THE CONFLICT, EVEN WITHOUT TCASII.

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.