Narrative:

We were flight planned at FL310. Departing pit, we were step-climbed to FL310. Then ZDC cleared us to FL350 and to expedite all the way up. I selected climb power and initiated a climb at the rate of 1000-1200 FPM. As expected, the speed 'bled off' as we traded airspeed for altitude. Approaching FL350, we entered an area of light to occasional moderate turbulence. We leveled at FL350 at a slower than normal speed, but still above clean speed for our weight. However, with climb power still selected, the aircraft would not accelerate and the airspeed actually began to decay to below clean speed. I directed the first officer to get clearance to a lower altitude. By now we were with ZTL and they could not immediately clear us lower. I initiated a descent slowly in VMC while the first officer declared an emergency to get lower. Shortly after departing FL350, the aircraft accelerated back to normal cruise mach and we were cleared to FL310. The rest of the flight continued without incident. We were advised to contact the FAA's quality assurance division to discuss a possible altitude deviation. I am not aware as to whether or not a loss of separation occurred with any other aircraft. However, I am convinced that staying at FL350 may very possibly have resulted in a much more serious situation.

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Original NASA ASRS Text

Title: AN MD80 CREW, UNABLE TO MAINTAIN FL350 DUE TO ACFT PERFORMANCE, DECLARED AN EMER IN ORDER TO RECEIVE IMMEDIATE DSCNT CLRNC.

Narrative: WE WERE FLT PLANNED AT FL310. DEPARTING PIT, WE WERE STEP-CLBED TO FL310. THEN ZDC CLRED US TO FL350 AND TO EXPEDITE ALL THE WAY UP. I SELECTED CLB PWR AND INITIATED A CLB AT THE RATE OF 1000-1200 FPM. AS EXPECTED, THE SPD 'BLED OFF' AS WE TRADED AIRSPD FOR ALT. APCHING FL350, WE ENTERED AN AREA OF LIGHT TO OCCASIONAL MODERATE TURB. WE LEVELED AT FL350 AT A SLOWER THAN NORMAL SPD, BUT STILL ABOVE CLEAN SPD FOR OUR WT. HOWEVER, WITH CLB PWR STILL SELECTED, THE ACFT WOULD NOT ACCELERATE AND THE AIRSPD ACTUALLY BEGAN TO DECAY TO BELOW CLEAN SPD. I DIRECTED THE FO TO GET CLRNC TO A LOWER ALT. BY NOW WE WERE WITH ZTL AND THEY COULD NOT IMMEDIATELY CLR US LOWER. I INITIATED A DSCNT SLOWLY IN VMC WHILE THE FO DECLARED AN EMER TO GET LOWER. SHORTLY AFTER DEPARTING FL350, THE ACFT ACCELERATED BACK TO NORMAL CRUISE MACH AND WE WERE CLRED TO FL310. THE REST OF THE FLT CONTINUED WITHOUT INCIDENT. WE WERE ADVISED TO CONTACT THE FAA'S QUALITY ASSURANCE DIVISION TO DISCUSS A POSSIBLE ALTDEV. I AM NOT AWARE AS TO WHETHER OR NOT A LOSS OF SEPARATION OCCURRED WITH ANY OTHER ACFT. HOWEVER, I AM CONVINCED THAT STAYING AT FL350 MAY VERY POSSIBLY HAVE RESULTED IN A MUCH MORE SERIOUS SIT.

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.