Narrative:

Operational error with same air carrier aircraft. Specialist issued the wrong altitude to the aircraft descending. The ntap reported the aircraft 1.2 mi and 200 ft. When observing replay of operational error, primary targets touched. I contacted the affected air carrier operations, and asked if they had any TCASII RA's with the involved aircraft. The airline stated no RA's were reported by the flight crew. These 2 aircraft were probably within 30 seconds of hitting and neither aircraft had an RA. One aircraft (aircraft Y) was level at 10000 ft. The second descending to 10000 ft (aircraft X) with a 100 KT overtake. Aircraft were inside msp approach but stated they always keep TCASII on RA. I'm concerned that TCASII was not a usable took to prevent an accident in midair over farmington, mn.

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Original NASA ASRS Text

Title: ZMP CTLR INADVERTENTLY DSNDS FOLLOWING ACR TO THE ALT OF THE PRECEDING ACR, WITH A 100 KT OVERTAKE. BOTH ACR'S ENTER MSP APCH CTL AIRSPACE WITH LTSS.

Narrative: OPERROR WITH SAME ACR ACFT. SPECIALIST ISSUED THE WRONG ALT TO THE ACFT DSNDING. THE NTAP RPTED THE ACFT 1.2 MI AND 200 FT. WHEN OBSERVING REPLAY OF OPERROR, PRIMARY TARGETS TOUCHED. I CONTACTED THE AFFECTED ACR OPS, AND ASKED IF THEY HAD ANY TCASII RA'S WITH THE INVOLVED ACFT. THE AIRLINE STATED NO RA'S WERE RPTED BY THE FLC. THESE 2 ACFT WERE PROBABLY WITHIN 30 SECONDS OF HITTING AND NEITHER ACFT HAD AN RA. ONE ACFT (ACFT Y) WAS LEVEL AT 10000 FT. THE SECOND DSNDING TO 10000 FT (ACFT X) WITH A 100 KT OVERTAKE. ACFT WERE INSIDE MSP APCH BUT STATED THEY ALWAYS KEEP TCASII ON RA. I'M CONCERNED THAT TCASII WAS NOT A USABLE TOOK TO PREVENT AN ACCIDENT IN MIDAIR OVER FARMINGTON, MN.

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.