Narrative:

We departed bos on runway 22L. Initial heading was 140 degrees, with eventual vectors to heading 270 degrees towards baf VOR. As we approached 6000 ft while climbing to 14000 ft we noticed another aircraft approaching from right to left at what appeared to be close to our altitude. At first we did not realize it was a small aircraft, an assumption that seemed to be confirmed by the lack of a TCASII return. Continued observation still produced no confirming TCASII return. By the time it became clear that this was indeed a small, close aircraft rather than a large, distant aircraft, it was too late to take effective evasive action. Since the aircraft was moving rapidly across the windscreen during the entire event we realized we were not on a collision course, although had we realized how close the aircraft was and would become, we most certainly would have attempted some type of evasive maneuver. The other aircraft passed in front of us, well within 1/2 mi horizontally and about 200-400 ft above us. We could clearly see that the aircraft was white with a blue aft fuselage and blue trim on the winglets. We believed it to be a canadair challenger. We asked departure to tell us who the aircraft was, and they responded that they showed no traffic. A further question revealed that they did have a primary target only. Upon our arrival in memphis, I called the departure control supervisor. He related that the aircraft had also departed boston, had not turned on its transponder (hence, no TCASII return), and had somehow lost radio contact. The controller apparently did not realize the aircraft was there (my assumption). When he told me the aircraft was a learjet I realized we may have come even closer than my estimate since we had assumed the aircraft was a 'widebody transport' challenger. This was a good example of relying too heavily on the TCASII. We are so used to confirming traffic by xchking the TCASII that we tend to not believe our eyes when what they tell us differs from the TCASII. After 4 near misses in the military, this was my fourth with the airline. I think that is enough!

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Original NASA ASRS Text

Title: FLC OF B727 SIGHTS AN ACFT FLYING ACROSS THEIR FLT PATH. AS IT GETS CLOSER THEY REALIZE IT IS A SMALLER ACFT BUT STILL GET NO TCASII INDICATIONS. QUERYING ATC THEY DETERMINE IT IS A LEARJET WHICH FAILED TO TURN ON ITS XPONDER.

Narrative: WE DEPARTED BOS ON RWY 22L. INITIAL HDG WAS 140 DEGS, WITH EVENTUAL VECTORS TO HDG 270 DEGS TOWARDS BAF VOR. AS WE APCHED 6000 FT WHILE CLBING TO 14000 FT WE NOTICED ANOTHER ACFT APCHING FROM R TO L AT WHAT APPEARED TO BE CLOSE TO OUR ALT. AT FIRST WE DID NOT REALIZE IT WAS A SMALL ACFT, AN ASSUMPTION THAT SEEMED TO BE CONFIRMED BY THE LACK OF A TCASII RETURN. CONTINUED OBSERVATION STILL PRODUCED NO CONFIRMING TCASII RETURN. BY THE TIME IT BECAME CLR THAT THIS WAS INDEED A SMALL, CLOSE ACFT RATHER THAN A LARGE, DISTANT ACFT, IT WAS TOO LATE TO TAKE EFFECTIVE EVASIVE ACTION. SINCE THE ACFT WAS MOVING RAPIDLY ACROSS THE WINDSCREEN DURING THE ENTIRE EVENT WE REALIZED WE WERE NOT ON A COLLISION COURSE, ALTHOUGH HAD WE REALIZED HOW CLOSE THE ACFT WAS AND WOULD BECOME, WE MOST CERTAINLY WOULD HAVE ATTEMPTED SOME TYPE OF EVASIVE MANEUVER. THE OTHER ACFT PASSED IN FRONT OF US, WELL WITHIN 1/2 MI HORIZLY AND ABOUT 200-400 FT ABOVE US. WE COULD CLRLY SEE THAT THE ACFT WAS WHITE WITH A BLUE AFT FUSELAGE AND BLUE TRIM ON THE WINGLETS. WE BELIEVED IT TO BE A CANADAIR CHALLENGER. WE ASKED DEP TO TELL US WHO THE ACFT WAS, AND THEY RESPONDED THAT THEY SHOWED NO TFC. A FURTHER QUESTION REVEALED THAT THEY DID HAVE A PRIMARY TARGET ONLY. UPON OUR ARR IN MEMPHIS, I CALLED THE DEP CTL SUPVR. HE RELATED THAT THE ACFT HAD ALSO DEPARTED BOSTON, HAD NOT TURNED ON ITS XPONDER (HENCE, NO TCASII RETURN), AND HAD SOMEHOW LOST RADIO CONTACT. THE CTLR APPARENTLY DID NOT REALIZE THE ACFT WAS THERE (MY ASSUMPTION). WHEN HE TOLD ME THE ACFT WAS A LEARJET I REALIZED WE MAY HAVE COME EVEN CLOSER THAN MY ESTIMATE SINCE WE HAD ASSUMED THE ACFT WAS A 'WDB' CHALLENGER. THIS WAS A GOOD EXAMPLE OF RELYING TOO HEAVILY ON THE TCASII. WE ARE SO USED TO CONFIRMING TFC BY XCHKING THE TCASII THAT WE TEND TO NOT BELIEVE OUR EYES WHEN WHAT THEY TELL US DIFFERS FROM THE TCASII. AFTER 4 NEAR MISSES IN THE MIL, THIS WAS MY FOURTH WITH THE AIRLINE. I THINK THAT IS ENOUGH!

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.