Narrative:

Our flight was proceeding uneventfully from rdg to lns. We were descending from 4000 ft for a visual approach, and were under the control of reading departure. The conflicting traffic we were about to encounter had not been reported to us by ATC. The first officer was the PF. I was looking for other aircraft. While I was reading the descent and approach checklists, I noticed movement out of the right 'corner' of my eyes. I could immediately tell we were not going to hit the other aircraft, but it was close. We did not take any evasive action because we had neither the time nor the need to do so. There was very little time to identify the other aircraft, except we could tell that it was a single engine low fixed wing. We were converging on an approximately 45 degree angle. We were descending from above the other aircraft. It is possible that we saw the other aircraft only at the last second because he was below our normal viewing capabilities out of the cockpit. It might have been below the windows. After the encounter I asked reading departure if they saw any other aircraft on their radar, and the controller said no. The other aircraft did not show up on the radar scope at reading, apparently. I intend to be even more vigilant in the future. I don't know why the other aircraft did not show up on reading's radar. I am aware of the requirements of the see-and-avoid concept.

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Original NASA ASRS Text

Title: ACR ON DSCNT HAS NMAC WITH SMA.

Narrative: OUR FLT WAS PROCEEDING UNEVENTFULLY FROM RDG TO LNS. WE WERE DSNDING FROM 4000 FT FOR A VISUAL APCH, AND WERE UNDER THE CTL OF READING DEP. THE CONFLICTING TFC WE WERE ABOUT TO ENCOUNTER HAD NOT BEEN RPTED TO US BY ATC. THE FO WAS THE PF. I WAS LOOKING FOR OTHER ACFT. WHILE I WAS READING THE DSCNT AND APCH CHKLISTS, I NOTICED MOVEMENT OUT OF THE R 'CORNER' OF MY EYES. I COULD IMMEDIATELY TELL WE WERE NOT GOING TO HIT THE OTHER ACFT, BUT IT WAS CLOSE. WE DID NOT TAKE ANY EVASIVE ACTION BECAUSE WE HAD NEITHER THE TIME NOR THE NEED TO DO SO. THERE WAS VERY LITTLE TIME TO IDENT THE OTHER ACFT, EXCEPT WE COULD TELL THAT IT WAS A SINGLE ENG LOW FIXED WING. WE WERE CONVERGING ON AN APPROX 45 DEG ANGLE. WE WERE DSNDING FROM ABOVE THE OTHER ACFT. IT IS POSSIBLE THAT WE SAW THE OTHER ACFT ONLY AT THE LAST SECOND BECAUSE HE WAS BELOW OUR NORMAL VIEWING CAPABILITIES OUT OF THE COCKPIT. IT MIGHT HAVE BEEN BELOW THE WINDOWS. AFTER THE ENCOUNTER I ASKED READING DEP IF THEY SAW ANY OTHER ACFT ON THEIR RADAR, AND THE CTLR SAID NO. THE OTHER ACFT DID NOT SHOW UP ON THE RADAR SCOPE AT READING, APPARENTLY. I INTEND TO BE EVEN MORE VIGILANT IN THE FUTURE. I DON'T KNOW WHY THE OTHER ACFT DID NOT SHOW UP ON READING'S RADAR. I AM AWARE OF THE REQUIREMENTS OF THE SEE-AND-AVOID CONCEPT.

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.