Narrative:

We departed atl for msp. Climbing out, we requested FL390 due to reports of turbulence at lower flight levels. FMGC showed FL385 as optimum altitude, FL391 maximum altitude (FL391 is maximum certified altitude for A320, not performance limit). ZTL requested climb through FL370 in less than 8 mins. This was complied with (in approximately 6 mins). Passing approximately FL380, ZTL asked how long until we could be level at FL390. We responded 'about 2 mins.' this was based on our present rate of climb. At approximately FL383 we encountered light turbulence and a possible loss of headwind. Airspeed decreased to 'green DOT' (minimum zero flap) and the aircraft stopped climbing at FL386. Aircraft would not climb or accelerate, although our FMGC was now showing FL390 as optimum altitude (gross weight 130000 pounds on ECAM display) and maximum continuous thrust was operating. ZTL asked us 3 times to 'report' or 'confirm' level at FL390. Each time we responded, 'level FL386.' sensing a traffic conflict, we offered to descend and were finally given a vector 30 degrees to the right. We were not notified of any conflict, but after being cleared back on course we were advised to call ZTL by telephone upon reaching EST. I called ZTL on arrival and was informed by ATC shift supervisor that a 'pilot deviation report' was being filed. I suspect that in addition to encountering light turbulence and a loss of headwind, our poor climb performance may have been due to a higher aircraft gross weight than indicated. Loss of vertical separation was due to controller's failure to initiate off-course vector soon enough. At high flight levels, our estimates of 'time to climb' can be very inaccurate under certain circumstances.

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Original NASA ASRS Text

Title: A320 FLC UNABLE TO COMPLY WITH ANTICIPATED LEVELOFF TIME.

Narrative: WE DEPARTED ATL FOR MSP. CLBING OUT, WE REQUESTED FL390 DUE TO RPTS OF TURB AT LOWER FLT LEVELS. FMGC SHOWED FL385 AS OPTIMUM ALT, FL391 MAX ALT (FL391 IS MAX CERTIFIED ALT FOR A320, NOT PERFORMANCE LIMIT). ZTL REQUESTED CLB THROUGH FL370 IN LESS THAN 8 MINS. THIS WAS COMPLIED WITH (IN APPROX 6 MINS). PASSING APPROX FL380, ZTL ASKED HOW LONG UNTIL WE COULD BE LEVEL AT FL390. WE RESPONDED 'ABOUT 2 MINS.' THIS WAS BASED ON OUR PRESENT RATE OF CLB. AT APPROX FL383 WE ENCOUNTERED LIGHT TURB AND A POSSIBLE LOSS OF HEADWIND. AIRSPD DECREASED TO 'GREEN DOT' (MINIMUM ZERO FLAP) AND THE ACFT STOPPED CLBING AT FL386. ACFT WOULD NOT CLB OR ACCELERATE, ALTHOUGH OUR FMGC WAS NOW SHOWING FL390 AS OPTIMUM ALT (GROSS WT 130000 LBS ON ECAM DISPLAY) AND MAX CONTINUOUS THRUST WAS OPERATING. ZTL ASKED US 3 TIMES TO 'RPT' OR 'CONFIRM' LEVEL AT FL390. EACH TIME WE RESPONDED, 'LEVEL FL386.' SENSING A TFC CONFLICT, WE OFFERED TO DSND AND WERE FINALLY GIVEN A VECTOR 30 DEGS TO THE R. WE WERE NOT NOTIFIED OF ANY CONFLICT, BUT AFTER BEING CLRED BACK ON COURSE WE WERE ADVISED TO CALL ZTL BY TELEPHONE UPON REACHING EST. I CALLED ZTL ON ARR AND WAS INFORMED BY ATC SHIFT SUPVR THAT A 'PLTDEV RPT' WAS BEING FILED. I SUSPECT THAT IN ADDITION TO ENCOUNTERING LIGHT TURB AND A LOSS OF HEADWIND, OUR POOR CLB PERFORMANCE MAY HAVE BEEN DUE TO A HIGHER ACFT GROSS WT THAN INDICATED. LOSS OF VERT SEPARATION WAS DUE TO CTLR'S FAILURE TO INITIATE OFF-COURSE VECTOR SOON ENOUGH. AT HIGH FLT LEVELS, OUR ESTIMATES OF 'TIME TO CLB' CAN BE VERY INACCURATE UNDER CERTAIN CIRCUMSTANCES.

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.