Narrative:

While being vectored for approach on heading 100 degrees, and descending to 6000 ft, when leaving about 6600 ft, we saw a C182 10-11 O'clock our position with no previous TCASII alert and/or ATC traffic information. This cessna was on a 210 degree heading and estimated on a level flight path at 6500 ft in that moment. We estimate that we crossed the other plane at 6400-6350 ft descending after disengaging the autoplt to increase our rate of descent while maintaining continuous visual contact, at the horizontal and vertical estimated distances previously mentioned. After informing ATC on frequency 128.40 MHZ (philadelphia approach) about this event, the controller reported to us that this traffic was not on the radar screen, not even the secondary echo. This could mean that the cessna didn't even have a transponder on while cruising (probably due to an in-flight transponder failure) and also never requested ATC clearance to fly in class B airspace. Another problem here, besides the proximity of the flight paths, is that not even the controller would have noticed this traffic had we not reported it, and this could mean that this kind of unauthorized flight could be a 'common' practice for this and maybe other pilots.

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Original NASA ASRS Text

Title: NMAC IN CLASS B AIRSPACE BTWN A B737-400 DSNDING THROUGH 6500 FT AND A C182 IN LEVEL FLT WITH NO XPONDER ON. ATC DID NOT HAVE PRIMARY OR SECONDARY TARGET ON THE C182 SO THEREFORE, MADE NO TA. RPTING CAPT INCREASED HIS RATE OF DSCNT TO HELP PREVENT A POTENTIAL COLLISION.

Narrative: WHILE BEING VECTORED FOR APCH ON HDG 100 DEGS, AND DSNDING TO 6000 FT, WHEN LEAVING ABOUT 6600 FT, WE SAW A C182 10-11 O'CLOCK OUR POS WITH NO PREVIOUS TCASII ALERT AND/OR ATC TFC INFO. THIS CESSNA WAS ON A 210 DEG HDG AND ESTIMATED ON A LEVEL FLT PATH AT 6500 FT IN THAT MOMENT. WE ESTIMATE THAT WE CROSSED THE OTHER PLANE AT 6400-6350 FT DSNDING AFTER DISENGAGING THE AUTOPLT TO INCREASE OUR RATE OF DSCNT WHILE MAINTAINING CONTINUOUS VISUAL CONTACT, AT THE HORIZ AND VERT ESTIMATED DISTANCES PREVIOUSLY MENTIONED. AFTER INFORMING ATC ON FREQ 128.40 MHZ (PHILADELPHIA APCH) ABOUT THIS EVENT, THE CTLR RPTED TO US THAT THIS TFC WAS NOT ON THE RADAR SCREEN, NOT EVEN THE SECONDARY ECHO. THIS COULD MEAN THAT THE CESSNA DIDN'T EVEN HAVE A XPONDER ON WHILE CRUISING (PROBABLY DUE TO AN INFLT XPONDER FAILURE) AND ALSO NEVER REQUESTED ATC CLRNC TO FLY IN CLASS B AIRSPACE. ANOTHER PROB HERE, BESIDES THE PROX OF THE FLT PATHS, IS THAT NOT EVEN THE CTLR WOULD HAVE NOTICED THIS TFC HAD WE NOT RPTED IT, AND THIS COULD MEAN THAT THIS KIND OF UNAUTH FLT COULD BE A 'COMMON' PRACTICE FOR THIS AND MAYBE OTHER PLTS.

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.