Narrative:

Climbing out of hou, fort worth center requested my planned cruise mach. I replied .76. He then asked an air carrier behind me what their planned cruise mach would be. He replied .78. Fort worth asked if we could maintain .78 or better and since the previous request involved cruise speed I replied affirmative. We were still climbing to FL350 at .74 mach when we entered icing conditions so that with the application of engine and wing anti-ice our climb speed rapidly deteriorated. Leaving FL332 fort worth requested my airspeed, which by then had deteriorated from 280 KTS to 230 KTS. He requested we level at FL330. We descended to 330. Fort worth later requested I call them on the telephone. Upon discussing the situation with the sector supervisor I discovered that fort worth had understood we were to climb and cruise at .78 mach or greater. Since the entire conversation prior to fort worth's speed request had involved cruise speed it never occurred to either the first officer or me that the speed assignment was immediate. The aircraft was incapable of climbing at .78 mach and had I understood the assignment to be a climb and cruise I would have so advised fort worth center.

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Original NASA ASRS Text

Title: ACR MLG REDUCED CLB SPD CAUSING SEPARATION PROBLEM WITH ACFT IN TRAIL.

Narrative: CLBING OUT OF HOU, FORT WORTH CENTER REQUESTED MY PLANNED CRUISE MACH. I REPLIED .76. HE THEN ASKED AN ACR BEHIND ME WHAT THEIR PLANNED CRUISE MACH WOULD BE. HE REPLIED .78. FORT WORTH ASKED IF WE COULD MAINTAIN .78 OR BETTER AND SINCE THE PREVIOUS REQUEST INVOLVED CRUISE SPD I REPLIED AFFIRMATIVE. WE WERE STILL CLBING TO FL350 AT .74 MACH WHEN WE ENTERED ICING CONDITIONS SO THAT WITH THE APPLICATION OF ENG AND WING ANTI-ICE OUR CLB SPD RAPIDLY DETERIORATED. LEAVING FL332 FORT WORTH REQUESTED MY AIRSPD, WHICH BY THEN HAD DETERIORATED FROM 280 KTS TO 230 KTS. HE REQUESTED WE LEVEL AT FL330. WE DSNDED TO 330. FORT WORTH LATER REQUESTED I CALL THEM ON THE TELEPHONE. UPON DISCUSSING THE SITUATION WITH THE SECTOR SUPVR I DISCOVERED THAT FORT WORTH HAD UNDERSTOOD WE WERE TO CLB AND CRUISE AT .78 MACH OR GREATER. SINCE THE ENTIRE CONVERSATION PRIOR TO FORT WORTH'S SPD REQUEST HAD INVOLVED CRUISE SPD IT NEVER OCCURRED TO EITHER THE FO OR ME THAT THE SPD ASSIGNMENT WAS IMMEDIATE. THE ACFT WAS INCAPABLE OF CLBING AT .78 MACH AND HAD I UNDERSTOOD THE ASSIGNMENT TO BE A CLB AND CRUISE I WOULD HAVE SO ADVISED FORT WORTH CENTER.

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.