Narrative:

Boston approach gave us a descent to 3000 ft MSL at lobby, and to expect the visual approach to runway 23 at bed. We were heading approximately 75 degrees direct to lobby. Passing through 4500 ft MSL, our TCASII gave us a TA on an aircraft below and to our right at 1.5 mi. The TCASII resolution directed us to descend at 1200-1400 FPM to avoid the traffic. I took this action at the same time the controller instructed us to climb to 4000 ft MSL. Simultaneously, the PNF acquired the traffic visually, and talked my eyes onto the traffic. The traffic was crossing right to left on a northerly heading. I immediately pulled to the right (south) so as to lag the collision course and further increase the lateral separation along with the TCASII command for vertical separation. The visual evasive action actually shallowed my descent to level flight, and we passed behind the cessna by approximately 550-1000 ft laterally, and slightly high on the flight path. It is of interest to note, that as my flight path shallowed out by my visual maneuvering, the TCASII commanded an immediate climb. I was impressed with the performance of the TCASII to this fluid maneuvering/environment. No prior warning of traffic was given to prevent this incident by approach control. If this had been a true IMC or non-visual event, I believed the TCASII was correct from my sight picture, and the commanded descent would have taken us right under the cessna without incurring a collision. The crossing angle was a true collision course, and would have placed us directly under the cessna's flight path. From my experience in flying fighters in the USAF, this would have been a definite violation of the rules of engagement 500 ft bubble. With the proximity of the ATC handoff to bedford tower, I was not able to talk with the controller and to inform him that we maneuvered off TCASII. I think from his replies on the radio after the incident, that he, too, knew it was a close encounter. TCASII training paid off. Follow the commands. The first thing that flashed through my mind as the TCASII commanded one direction and the controller directed another, was the mid air in germany last yr. My PNF did a great job on visually acquiring the traffic, and contributed to increasing the miss distance through good verbal directions. He was prepared to take the evasive action visually if I had not done so, and I had not verbalized my actions to him at the given moment. His hands were 'resting' on the yoke. As we approached bed, on the extended right base to runway 23. We flew right over the top of a mooney that was on the right downwind to runway 23. The ATC tower controller was overloaded with departures, arrs, and VFR patterns. We were advised by tower of the traffic at the last min and avoided that conflict visually, with the aid of TCASII traffic call. This was my first trip to bedford.

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Original NASA ASRS Text

Title: LJ45 CREW HAD 2 TCASII EVENTS ARRIVING AT BED.

Narrative: BOSTON APCH GAVE US A DSCNT TO 3000 FT MSL AT LOBBY, AND TO EXPECT THE VISUAL APCH TO RWY 23 AT BED. WE WERE HEADING APPROX 75 DEGS DIRECT TO LOBBY. PASSING THROUGH 4500 FT MSL, OUR TCASII GAVE US A TA ON AN ACFT BELOW AND TO OUR R AT 1.5 MI. THE TCASII RESOLUTION DIRECTED US TO DSND AT 1200-1400 FPM TO AVOID THE TFC. I TOOK THIS ACTION AT THE SAME TIME THE CTLR INSTRUCTED US TO CLB TO 4000 FT MSL. SIMULTANEOUSLY, THE PNF ACQUIRED THE TFC VISUALLY, AND TALKED MY EYES ONTO THE TFC. THE TFC WAS XING R TO L ON A NORTHERLY HDG. I IMMEDIATELY PULLED TO THE R (S) SO AS TO LAG THE COLLISION COURSE AND FURTHER INCREASE THE LATERAL SEPARATION ALONG WITH THE TCASII COMMAND FOR VERT SEPARATION. THE VISUAL EVASIVE ACTION ACTUALLY SHALLOWED MY DSCNT TO LEVEL FLT, AND WE PASSED BEHIND THE CESSNA BY APPROX 550-1000 FT LATERALLY, AND SLIGHTLY HIGH ON THE FLT PATH. IT IS OF INTEREST TO NOTE, THAT AS MY FLT PATH SHALLOWED OUT BY MY VISUAL MANEUVERING, THE TCASII COMMANDED AN IMMEDIATE CLB. I WAS IMPRESSED WITH THE PERFORMANCE OF THE TCASII TO THIS FLUID MANEUVERING/ENVIRONMENT. NO PRIOR WARNING OF TFC WAS GIVEN TO PREVENT THIS INCIDENT BY APCH CTL. IF THIS HAD BEEN A TRUE IMC OR NON-VISUAL EVENT, I BELIEVED THE TCASII WAS CORRECT FROM MY SIGHT PICTURE, AND THE COMMANDED DSCNT WOULD HAVE TAKEN US RIGHT UNDER THE CESSNA WITHOUT INCURRING A COLLISION. THE XING ANGLE WAS A TRUE COLLISION COURSE, AND WOULD HAVE PLACED US DIRECTLY UNDER THE CESSNA'S FLT PATH. FROM MY EXPERIENCE IN FLYING FIGHTERS IN THE USAF, THIS WOULD HAVE BEEN A DEFINITE VIOLATION OF THE RULES OF ENGAGEMENT 500 FT BUBBLE. WITH THE PROX OF THE ATC HDOF TO BEDFORD TWR, I WAS NOT ABLE TO TALK WITH THE CTLR AND TO INFORM HIM THAT WE MANEUVERED OFF TCASII. I THINK FROM HIS REPLIES ON THE RADIO AFTER THE INCIDENT, THAT HE, TOO, KNEW IT WAS A CLOSE ENCOUNTER. TCASII TRAINING PAID OFF. FOLLOW THE COMMANDS. THE FIRST THING THAT FLASHED THROUGH MY MIND AS THE TCASII COMMANDED ONE DIRECTION AND THE CTLR DIRECTED ANOTHER, WAS THE MID AIR IN GERMANY LAST YR. MY PNF DID A GREAT JOB ON VISUALLY ACQUIRING THE TFC, AND CONTRIBUTED TO INCREASING THE MISS DISTANCE THROUGH GOOD VERBAL DIRECTIONS. HE WAS PREPARED TO TAKE THE EVASIVE ACTION VISUALLY IF I HAD NOT DONE SO, AND I HAD NOT VERBALIZED MY ACTIONS TO HIM AT THE GIVEN MOMENT. HIS HANDS WERE 'RESTING' ON THE YOKE. AS WE APCHED BED, ON THE EXTENDED R BASE TO RWY 23. WE FLEW RIGHT OVER THE TOP OF A MOONEY THAT WAS ON THE R DOWNWIND TO RWY 23. THE ATC TWR CTLR WAS OVERLOADED WITH DEPS, ARRS, AND VFR PATTERNS. WE WERE ADVISED BY TWR OF THE TFC AT THE LAST MIN AND AVOIDED THAT CONFLICT VISUALLY, WITH THE AID OF TCASII TFC CALL. THIS WAS MY FIRST TRIP TO BEDFORD.

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.