Narrative:

While acting as PIC for commuter flight we departed boston climbing to 4000 ft. We were assigned a heading of 360 degrees for traffic which was in our 12-2 O'clock position at 4700 ft. With traffic in sight, we were cleared to climb to 12000 ft while maintaining visual separation. Also, a direct pease when able was received. An air carrier Y flight was advised that we would be approaching from their 6 O'clock position and would be overtaking them while maintaining visual separation. Shortly after that, air carrier Y asked the controllers if they showed traffic near them. Once again the controller advised them of us. We kept them on our left side, passed on their right at a safe distance. Air carrier Y changed their course to the left and descended. Since we were still below them at the time (and climbing), their descent did bring us a little closer, but at no time was safety compromised. Air carrier Y reported that their TCASII advised them of traffic. I did tell the air carrier Y crew they should get their equipment checked. If indeed their TCASII told them to descend and turn left, one would have to question the reliability of the TCASII equipment in a real collision avoidance situation. Our aircraft was not equipped with TCASII.

Google
 

Original NASA ASRS Text

Title: COMMUTER HAS CLOSE PROX WITH ACR ACFT RESPONDING TO TCASII.

Narrative: WHILE ACTING AS PIC FOR COMMUTER FLT WE DEPARTED BOSTON CLBING TO 4000 FT. WE WERE ASSIGNED A HDG OF 360 DEGS FOR TFC WHICH WAS IN OUR 12-2 O'CLOCK POS AT 4700 FT. WITH TFC IN SIGHT, WE WERE CLRED TO CLB TO 12000 FT WHILE MAINTAINING VISUAL SEPARATION. ALSO, A DIRECT PEASE WHEN ABLE WAS RECEIVED. AN ACR Y FLT WAS ADVISED THAT WE WOULD BE APCHING FROM THEIR 6 O'CLOCK POS AND WOULD BE OVERTAKING THEM WHILE MAINTAINING VISUAL SEPARATION. SHORTLY AFTER THAT, ACR Y ASKED THE CTLRS IF THEY SHOWED TFC NEAR THEM. ONCE AGAIN THE CTLR ADVISED THEM OF US. WE KEPT THEM ON OUR L SIDE, PASSED ON THEIR R AT A SAFE DISTANCE. ACR Y CHANGED THEIR COURSE TO THE L AND DSNDED. SINCE WE WERE STILL BELOW THEM AT THE TIME (AND CLBING), THEIR DSCNT DID BRING US A LITTLE CLOSER, BUT AT NO TIME WAS SAFETY COMPROMISED. ACR Y RPTED THAT THEIR TCASII ADVISED THEM OF TFC. I DID TELL THE ACR Y CREW THEY SHOULD GET THEIR EQUIP CHKED. IF INDEED THEIR TCASII TOLD THEM TO DSND AND TURN L, ONE WOULD HAVE TO QUESTION THE RELIABILITY OF THE TCASII EQUIP IN A REAL COLLISION AVOIDANCE SIT. OUR ACFT WAS NOT EQUIPPED WITH TCASII.

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.