Narrative:

I issued climb clearance to air carrier X to FL330. Upon accepting handoff on air carrier Y southbound at FL310, I instructed air carrier X to 'expedite climb'. After running out vector lengths on 2 aircraft, I determined a climb rate of 1500 FPM was necessary for separation. I told air carrier X 'I need 1500 FPM or greater in climb to FL330, if unable advise'. Air carrier X responded, 'will comply'. At a point 3 mins later I noticed air carrier X's climb rate slowed. I asked if he was still climbing 1500 FPM and he said, 'no climbing 500 FPM'. I issued turns, but separation was lost. Note: I based separation of these 2 aircraft on air carrier X's compliance to my clearance. In my opinion, air carrier X's non compliance was the sole contributing factor in this operational error. Supplemental information from acn 116929: controller asked if we could maintain 1500 FPM climb to FL330. First officer flying and operating pms checked, and said we could. I told ATC we could comply. He then cleared us to FL330. We initially were able to climb at a rate of 3000 FPM on performance climb, but it soon bled off, that bled off, that by the time we reached FL320, we were unable to climb. We would get an intermittent climb of approximately 500 FPM.

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Original NASA ASRS Text

Title: ACR FAILED TO COMPLY WITH ATC CLRNC RESULTING IN LESS THAN STANDARD SEPARATION WITH ANOTHER ACFT.

Narrative: I ISSUED CLIMB CLRNC TO ACR X TO FL330. UPON ACCEPTING HANDOFF ON ACR Y SBND AT FL310, I INSTRUCTED ACR X TO 'EXPEDITE CLIMB'. AFTER RUNNING OUT VECTOR LENGTHS ON 2 ACFT, I DETERMINED A CLIMB RATE OF 1500 FPM WAS NECESSARY FOR SEPARATION. I TOLD ACR X 'I NEED 1500 FPM OR GREATER IN CLIMB TO FL330, IF UNABLE ADVISE'. ACR X RESPONDED, 'WILL COMPLY'. AT A POINT 3 MINS LATER I NOTICED ACR X'S CLIMB RATE SLOWED. I ASKED IF HE WAS STILL CLIMBING 1500 FPM AND HE SAID, 'NO CLIMBING 500 FPM'. I ISSUED TURNS, BUT SEPARATION WAS LOST. NOTE: I BASED SEPARATION OF THESE 2 ACFT ON ACR X'S COMPLIANCE TO MY CLRNC. IN MY OPINION, ACR X'S NON COMPLIANCE WAS THE SOLE CONTRIBUTING FACTOR IN THIS OPERATIONAL ERROR. SUPPLEMENTAL INFORMATION FROM ACN 116929: CTLR ASKED IF WE COULD MAINTAIN 1500 FPM CLIMB TO FL330. F/O FLYING AND OPERATING PMS CHECKED, AND SAID WE COULD. I TOLD ATC WE COULD COMPLY. HE THEN CLRED US TO FL330. WE INITIALLY WERE ABLE TO CLIMB AT A RATE OF 3000 FPM ON PERFORMANCE CLIMB, BUT IT SOON BLED OFF, THAT BLED OFF, THAT BY THE TIME WE REACHED FL320, WE WERE UNABLE TO CLIMB. WE WOULD GET AN INTERMITTENT CLIMB OF APPROX 500 FPM.

Data retrieved from NASA's ASRS site as of August 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.