Narrative:

I received a handoff from sector 14 on 2 northbound air carrier's. The higher air carrier X was blocking altitudes FL310/350 and tracking a gndspd of 485 KTS. The lower air carrier Y was at FL280 and overtaking at 558 KTS. Light to moderate turbulence had been reported in the sector for several hours between FL230 and FL370. When the aircraft were approximately 7 mi apart, the slower air carrier X, which was at the 10 O'clock position of the air carrier Y, asked for FL220. I issued the slower air carrier X a 30 degree turn to the left and a descent to FL240, followed by an immediate 15 degree turn to the right for air carrier Y. Both aircraft responded. When it appeared the turns were not taking as immediate effect as I thought, I observed air carrier X on the edge of the 5 mi 'J' ring of air carrier Y descending through FL299. I attempted to stop the descent of air carrier X but the pilot evidently was transmitting that he was encountering moderate turbulence, and did not copy the clearance to maintain FL290. I should have issued the higher/slower air carrier X a descent to FL290 initially until the turns were complete for both aircraft, and a 5 mi min distance was observed. I was in a hurry to get the higher aircraft out of the turbulence.

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Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACR Y. SYS ERROR. ACR X DSCNT THROUGH OCCUPIED ALT.

Narrative: I RECEIVED A HDOF FROM SECTOR 14 ON 2 NBOUND ACR'S. THE HIGHER ACR X WAS BLOCKING ALTS FL310/350 AND TRACKING A GNDSPD OF 485 KTS. THE LOWER ACR Y WAS AT FL280 AND OVERTAKING AT 558 KTS. LIGHT TO MODERATE TURB HAD BEEN RPTED IN THE SECTOR FOR SEVERAL HRS BTWN FL230 AND FL370. WHEN THE ACFT WERE APPROX 7 MI APART, THE SLOWER ACR X, WHICH WAS AT THE 10 O'CLOCK POS OF THE ACR Y, ASKED FOR FL220. I ISSUED THE SLOWER ACR X A 30 DEG TURN TO THE L AND A DSCNT TO FL240, FOLLOWED BY AN IMMEDIATE 15 DEG TURN TO THE R FOR ACR Y. BOTH ACFT RESPONDED. WHEN IT APPEARED THE TURNS WERE NOT TAKING AS IMMEDIATE EFFECT AS I THOUGHT, I OBSERVED ACR X ON THE EDGE OF THE 5 MI 'J' RING OF ACR Y DSNDING THROUGH FL299. I ATTEMPTED TO STOP THE DSCNT OF ACR X BUT THE PLT EVIDENTLY WAS XMITTING THAT HE WAS ENCOUNTERING MODERATE TURB, AND DID NOT COPY THE CLRNC TO MAINTAIN FL290. I SHOULD HAVE ISSUED THE HIGHER/SLOWER ACR X A DSCNT TO FL290 INITIALLY UNTIL THE TURNS WERE COMPLETE FOR BOTH ACFT, AND A 5 MI MIN DISTANCE WAS OBSERVED. I WAS IN A HURRY TO GET THE HIGHER ACFT OUT OF THE TURB.

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.