Narrative:

On fri, nov/xx/97 at XX10, a situation developed and a loss of standard separation (5 mi horizontal, 2000 ft vertical above FL290) occurred between air carrier X and cpr Y about 20 mi northwest of the mip VOR. I am a radar instructor and at the time of occurrence I was giving training to a developmental. Cpr Y was swbound on J49 about 30 mi northeast of psb VOR at FL310. Air carrier X was 20 mi west of the mip VOR flying the mip 1 arrival into lga at FL330. The developmental issued air carrier X a left turn to 360 degrees, a speed of 250 KTS, and a descent clearance to FL220. Air carrier X read this clearance back correctly. As the instructor, I initiated an expedite descent clearance through FL290 to air carrier X when both aircraft were approximately 8-9 mi apart converging. Air carrier X acknowledged this clearance. At the time the expedite clearance was issued, air carrier X data block showed an altitude mode C of FL312. (Remember, the information displayed is 6- 12 seconds old, also air carrier X descent rate prior to the expedite clearance was approximately 1500 FPM.) if I had done nothing and both cpr Y and air carrier X had not reacted to their individual resolutions, they would have crossed with at least 1000-1500 ft separation. Knowing of TCASII sensitivity and proximity of both aircraft, I initiated a TA to cpr Y first, then a TA to air carrier X. Air carrier X acknowledged with reacting to a TCASII resolution and was climbing. Cpr Y responded also by reacting to an RA. I feel air carrier X was already reacting to TCASII prior to expedite clearance through FL290 but still acknowledged the expedite clearance. I also feel that even though standard separation may have been strained, TCASII hindered this situation and made it a lot closer than it should have. It is my understanding that air carrier X filed a near miss report.

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Original NASA ASRS Text

Title: OJT INSTRUCTOR INTERVENED WHEN TRAINEE CTLR ACTIONS WERE BELIEVED INSUFFICIENT WHEN DISCONTINUING VERT SEPARATION BTWN A B737 AND A XING DA20. THE B737 AND DA20 INDIVIDUALLY REACTED TO TCASII RA'S. INSTRUCTOR ASSERTS TCASII RA'S HINDERED CTLR ACTIONS, MAKING SIT CLOSER THAN IT SHOULD HAVE BEEN.

Narrative: ON FRI, NOV/XX/97 AT XX10, A SIT DEVELOPED AND A LOSS OF STANDARD SEPARATION (5 MI HORIZ, 2000 FT VERT ABOVE FL290) OCCURRED BTWN ACR X AND CPR Y ABOUT 20 MI NW OF THE MIP VOR. I AM A RADAR INSTRUCTOR AND AT THE TIME OF OCCURRENCE I WAS GIVING TRAINING TO A DEVELOPMENTAL. CPR Y WAS SWBOUND ON J49 ABOUT 30 MI NE OF PSB VOR AT FL310. ACR X WAS 20 MI W OF THE MIP VOR FLYING THE MIP 1 ARR INTO LGA AT FL330. THE DEVELOPMENTAL ISSUED ACR X A L TURN TO 360 DEGS, A SPD OF 250 KTS, AND A DSCNT CLRNC TO FL220. ACR X READ THIS CLRNC BACK CORRECTLY. AS THE INSTRUCTOR, I INITIATED AN EXPEDITE DSCNT CLRNC THROUGH FL290 TO ACR X WHEN BOTH ACFT WERE APPROX 8-9 MI APART CONVERGING. ACR X ACKNOWLEDGED THIS CLRNC. AT THE TIME THE EXPEDITE CLRNC WAS ISSUED, ACR X DATA BLOCK SHOWED AN ALT MODE C OF FL312. (REMEMBER, THE INFO DISPLAYED IS 6- 12 SECONDS OLD, ALSO ACR X DSCNT RATE PRIOR TO THE EXPEDITE CLRNC WAS APPROX 1500 FPM.) IF I HAD DONE NOTHING AND BOTH CPR Y AND ACR X HAD NOT REACTED TO THEIR INDIVIDUAL RESOLUTIONS, THEY WOULD HAVE CROSSED WITH AT LEAST 1000-1500 FT SEPARATION. KNOWING OF TCASII SENSITIVITY AND PROX OF BOTH ACFT, I INITIATED A TA TO CPR Y FIRST, THEN A TA TO ACR X. ACR X ACKNOWLEDGED WITH REACTING TO A TCASII RESOLUTION AND WAS CLBING. CPR Y RESPONDED ALSO BY REACTING TO AN RA. I FEEL ACR X WAS ALREADY REACTING TO TCASII PRIOR TO EXPEDITE CLRNC THROUGH FL290 BUT STILL ACKNOWLEDGED THE EXPEDITE CLRNC. I ALSO FEEL THAT EVEN THOUGH STANDARD SEPARATION MAY HAVE BEEN STRAINED, TCASII HINDERED THIS SIT AND MADE IT A LOT CLOSER THAN IT SHOULD HAVE. IT IS MY UNDERSTANDING THAT ACR X FILED A NEAR MISS RPT.

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.