Narrative:

Our flight was level at 17000' as assigned, navigating direct cmk VOR as cleared. No traffic had been issued. I was flying the aircraft from the left seat. The first officer was reading back a change of frequency to the next center sector. I looked up from a scan of the engine gauges (center panel) and observed, through the center windscreen section, an unidentified aircraft passed across our front left to right. I called the traffic and the first officer observed it as the target opened very rapidly to our right. We did not make the assigned frequency switch, instead I asked our sector control (133.1) if any traffic was observed our vicinity. The initial response was negative traffic. I then declared the near miss. Bos center then came back saying a 1200 code had just then appeared on the radar, and to stay with them on the present frequency while they took down details. Our view of the other aircraft was extremely brief, making identify difficult, since it went almost immediately to a tail on aspect and falling rapidly behind our right side. Our impression was of a medium sized, light colored low wing twin propeller. We took no evasive action, there was no time to do so. My estimate of the target track, 90 degrees left to right to our 140 degree maximum allowable course, which would put it on a south westerly heading. My main concern is the failure of ATC radar to adequately warn us of a possible conflict. I believe it reasonable to assume the aircraft had been showing 1200 on the transponder prior to passing our position. A possible factor: the aircraft we were flying had been released in accordance to approved MEL, with an inoperative autoplt pitch axis. This necessitated extra head in the cockpit time to manually maintain altitude (especially with the switch program waiting to violate us!). Whether or not I would have seen the traffic earlier west/O this situation is, of course, unknown. But, given the traffic environment we have today, perhaps this type of MEL is too liberal.

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Original NASA ASRS Text

Title: MLG OBSERVED AN SMT CROSS HIS FLT PATH IN CLOSE PROX. NO ADVISORY FROM ARTCC CTLR AND NO TIME FOR EVASIVE ACTION. NMAC REPORTED BY MLG.

Narrative: OUR FLT WAS LEVEL AT 17000' AS ASSIGNED, NAVIGATING DIRECT CMK VOR AS CLRED. NO TFC HAD BEEN ISSUED. I WAS FLYING THE ACFT FROM THE LEFT SEAT. THE F/O WAS READING BACK A CHANGE OF FREQ TO THE NEXT CENTER SECTOR. I LOOKED UP FROM A SCAN OF THE ENG GAUGES (CENTER PANEL) AND OBSERVED, THROUGH THE CENTER WINDSCREEN SECTION, AN UNIDENTIFIED ACFT PASSED ACROSS OUR FRONT LEFT TO RIGHT. I CALLED THE TFC AND THE F/O OBSERVED IT AS THE TARGET OPENED VERY RAPIDLY TO OUR RIGHT. WE DID NOT MAKE THE ASSIGNED FREQ SWITCH, INSTEAD I ASKED OUR SECTOR CTL (133.1) IF ANY TFC WAS OBSERVED OUR VICINITY. THE INITIAL RESPONSE WAS NEGATIVE TFC. I THEN DECLARED THE NEAR MISS. BOS CENTER THEN CAME BACK SAYING A 1200 CODE HAD JUST THEN APPEARED ON THE RADAR, AND TO STAY WITH THEM ON THE PRESENT FREQ WHILE THEY TOOK DOWN DETAILS. OUR VIEW OF THE OTHER ACFT WAS EXTREMELY BRIEF, MAKING IDENT DIFFICULT, SINCE IT WENT ALMOST IMMEDIATELY TO A TAIL ON ASPECT AND FALLING RAPIDLY BEHIND OUR RIGHT SIDE. OUR IMPRESSION WAS OF A MEDIUM SIZED, LIGHT COLORED LOW WING TWIN PROP. WE TOOK NO EVASIVE ACTION, THERE WAS NO TIME TO DO SO. MY ESTIMATE OF THE TARGET TRACK, 90 DEGS LEFT TO RIGHT TO OUR 140 DEG MAXIMUM ALLOWABLE COURSE, WHICH WOULD PUT IT ON A S WESTERLY HDG. MY MAIN CONCERN IS THE FAILURE OF ATC RADAR TO ADEQUATELY WARN US OF A POSSIBLE CONFLICT. I BELIEVE IT REASONABLE TO ASSUME THE ACFT HAD BEEN SHOWING 1200 ON THE TRANSPONDER PRIOR TO PASSING OUR POS. A POSSIBLE FACTOR: THE ACFT WE WERE FLYING HAD BEEN RELEASED IN ACCORDANCE TO APPROVED MEL, WITH AN INOP AUTOPLT PITCH AXIS. THIS NECESSITATED EXTRA HEAD IN THE COCKPIT TIME TO MANUALLY MAINTAIN ALT (ESPECIALLY WITH THE SWITCH PROGRAM WAITING TO VIOLATE US!). WHETHER OR NOT I WOULD HAVE SEEN THE TFC EARLIER W/O THIS SITUATION IS, OF COURSE, UNKNOWN. BUT, GIVEN THE TFC ENVIRONMENT WE HAVE TODAY, PERHAPS THIS TYPE OF MEL IS TOO LIBERAL.

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.