Narrative:

Air carrier X (DC9) was climbing out of pit en route to msp and was initially vectored for additional traffic. Then with approximately 600 ft left to FL350, was cleared to resume navigation direct crl. Air carrier Y (B727) en route from ord to dca at FL330 was cleared direct air approximately 30 mi from air carrier X. After witnessing air carrier X's sluggish climb rate I told air carrier X to reach FL350 in 1 min. Pilot responded 'wilco.' air carrier X was at FL344 at this point. Still sluggish in the climb air carrier X was turned from approximately a 328 degree heading to a 010 degree heading. Air carrier Y was turned from approximately a 130 degree heading to a 200 degree heading. After approximately 1 min air carrier X was at FL347. It took air carrier X 1 min 50 seconds to level at FL350. He leveled at FL347 for approximately 40 seconds. After stating he would comply with the 1 min clearance the pilot never advised he could not climb 600 ft in 1 min. Because of the density and complexity of traffic over cleveland, high climb rates and descent rates are needed to separate traffic. Pilots understand this and consistently advise if they can't make clrncs. 600 ft in 1 min isn't asking a lot. Pilot of air carrier X later stated he thought he could make the clearance when issued. However, he never advised upon realizing he could not.

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Original NASA ASRS Text

Title: AN ACR DC9 OUT OF FL344 AND CLBING TO FL350 WAS ISSUED CLRNC TO BE LEVEL AT FL350 IN 1 MIN DUE TO OPPOSITE DIRECTION TFC AT FL330. AFTER CLOSE TO 2 MINS, THE CTLR OBSERVED THAT THE DC9 HAD NOT REACHED FL350, AND ISSUED VECTOR HEADINGS TO BOTH ACFT IN AN ATTEMPT TO MAINTAIN SEPARATION, HOWEVER, SEPARATION WAS LOST.

Narrative: ACR X (DC9) WAS CLBING OUT OF PIT ENRTE TO MSP AND WAS INITIALLY VECTORED FOR ADDITIONAL TFC. THEN WITH APPROX 600 FT LEFT TO FL350, WAS CLRED TO RESUME NAV DIRECT CRL. ACR Y (B727) ENRTE FROM ORD TO DCA AT FL330 WAS CLRED DIRECT AIR APPROX 30 MI FROM ACR X. AFTER WITNESSING ACR X'S SLUGGISH CLB RATE I TOLD ACR X TO REACH FL350 IN 1 MIN. PLT RESPONDED 'WILCO.' ACR X WAS AT FL344 AT THIS POINT. STILL SLUGGISH IN THE CLB ACR X WAS TURNED FROM APPROX A 328 DEG HDG TO A 010 DEG HDG. ACR Y WAS TURNED FROM APPROX A 130 DEG HDG TO A 200 DEG HDG. AFTER APPROX 1 MIN ACR X WAS AT FL347. IT TOOK ACR X 1 MIN 50 SECONDS TO LEVEL AT FL350. HE LEVELED AT FL347 FOR APPROX 40 SECONDS. AFTER STATING HE WOULD COMPLY WITH THE 1 MIN CLRNC THE PLT NEVER ADVISED HE COULD NOT CLB 600 FT IN 1 MIN. BECAUSE OF THE DENSITY AND COMPLEXITY OF TFC OVER CLEVELAND, HIGH CLB RATES AND DSCNT RATES ARE NEEDED TO SEPARATE TFC. PLTS UNDERSTAND THIS AND CONSISTENTLY ADVISE IF THEY CAN'T MAKE CLRNCS. 600 FT IN 1 MIN ISN'T ASKING A LOT. PLT OF ACR X LATER STATED HE THOUGHT HE COULD MAKE THE CLRNC WHEN ISSUED. HOWEVER, HE NEVER ADVISED UPON REALIZING HE COULD NOT.

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.