Narrative:

Departed jax en route to dtw. Climbing to FL330. We were heavy and the outside air temperature was warmer than normal (ram air temperature at FL310 was -18 degrees C). I was the PF and tried to maintain 1000 FPM climb. When the indicated airspeed decreased below 250 KIAS, I adjusted the autoplt to command slightly less than 1000 FPM climb. Passing approximately FL310, the airspeed slowed below 240 KTS, and I commanded the autoplt to climb at 500 FPM. Passing approximately FL320, airspeed slowed to 230 KTS, and I commanded as slow of a rate of climb as I could on the autoplt. Soon after, I heard a vibration (note: I did not 'feel' it at this initial onset). I thought to myself 'could this be a buffet, or is it the oven in the galley behind me making the noise?' it soon became apparent it was a buffet. By this time we were at FL328. I commanded level flight on the autoplt and told the captain 'I'll tweak the altitude when we pick up speed.' I noticed the captain had his hand on the control wheel and I asked him 'do you want the aircraft?' he replied 'no you have the aircraft.' I realized then that he had his hand there for the push-to-talk microphone button (not to take over control) and was trying to get a word in to ATC to request lower. Soon after, the captain commanded 'take it down to FL310 now.' I disconnected the autoplt and gladly complied with his request. Captain got the word in to ATC requesting FL310 and was granted FL310. Aircraft increased speed, buffet stopped, we leveled at FL310. Lessons learned: next time I don't get the climb performance needed to maintain 1000 FPM climb at target/efficient climb speed, I'll be quick to ask that we get ATC's permission to climb at a lesser rate. Even though our airspeed was above the 1.3 buffet chart speed for our weight, the performance was less than normal. Hindsight tells me that this was due to the warmer than normal temperature for the flight level. Again I say, when I'm in an airplane that is not performing as planned, I will be more aggressive in slowing the rate of climb (leveloff if necessary).

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Original NASA ASRS Text

Title: DC9 CREW UNABLE TO CLB TO PLANNED CRUISE ALT, DUE TO DECREASED ACFT PERFORMANCE.

Narrative: DEPARTED JAX ENRTE TO DTW. CLBING TO FL330. WE WERE HVY AND THE OUTSIDE AIR TEMP WAS WARMER THAN NORMAL (RAM AIR TEMP AT FL310 WAS -18 DEGS C). I WAS THE PF AND TRIED TO MAINTAIN 1000 FPM CLB. WHEN THE INDICATED AIRSPD DECREASED BELOW 250 KIAS, I ADJUSTED THE AUTOPLT TO COMMAND SLIGHTLY LESS THAN 1000 FPM CLB. PASSING APPROX FL310, THE AIRSPD SLOWED BELOW 240 KTS, AND I COMMANDED THE AUTOPLT TO CLB AT 500 FPM. PASSING APPROX FL320, AIRSPD SLOWED TO 230 KTS, AND I COMMANDED AS SLOW OF A RATE OF CLB AS I COULD ON THE AUTOPLT. SOON AFTER, I HEARD A VIBRATION (NOTE: I DID NOT 'FEEL' IT AT THIS INITIAL ONSET). I THOUGHT TO MYSELF 'COULD THIS BE A BUFFET, OR IS IT THE OVEN IN THE GALLEY BEHIND ME MAKING THE NOISE?' IT SOON BECAME APPARENT IT WAS A BUFFET. BY THIS TIME WE WERE AT FL328. I COMMANDED LEVEL FLT ON THE AUTOPLT AND TOLD THE CAPT 'I'LL TWEAK THE ALT WHEN WE PICK UP SPD.' I NOTICED THE CAPT HAD HIS HAND ON THE CTL WHEEL AND I ASKED HIM 'DO YOU WANT THE ACFT?' HE REPLIED 'NO YOU HAVE THE ACFT.' I REALIZED THEN THAT HE HAD HIS HAND THERE FOR THE PUSH-TO-TALK MIKE BUTTON (NOT TO TAKE OVER CTL) AND WAS TRYING TO GET A WORD IN TO ATC TO REQUEST LOWER. SOON AFTER, THE CAPT COMMANDED 'TAKE IT DOWN TO FL310 NOW.' I DISCONNECTED THE AUTOPLT AND GLADLY COMPLIED WITH HIS REQUEST. CAPT GOT THE WORD IN TO ATC REQUESTING FL310 AND WAS GRANTED FL310. ACFT INCREASED SPD, BUFFET STOPPED, WE LEVELED AT FL310. LESSONS LEARNED: NEXT TIME I DON'T GET THE CLB PERFORMANCE NEEDED TO MAINTAIN 1000 FPM CLB AT TARGET/EFFICIENT CLB SPD, I'LL BE QUICK TO ASK THAT WE GET ATC'S PERMISSION TO CLB AT A LESSER RATE. EVEN THOUGH OUR AIRSPD WAS ABOVE THE 1.3 BUFFET CHART SPD FOR OUR WT, THE PERFORMANCE WAS LESS THAN NORMAL. HINDSIGHT TELLS ME THAT THIS WAS DUE TO THE WARMER THAN NORMAL TEMP FOR THE FLT LEVEL. AGAIN I SAY, WHEN I'M IN AN AIRPLANE THAT IS NOT PERFORMING AS PLANNED, I WILL BE MORE AGGRESSIVE IN SLOWING THE RATE OF CLB (LEVELOFF IF NECESSARY).

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.