Narrative:

After climbing to FL350 and being level for some time, the first officer (PF) noticed that following a shallow turn the aircraft was slowly losing airspeed. We set maximum continuous thrust (mct), but it appeared that the airspeed loss could not be stopped. I notified center that we would require a lower altitude. Center said we could only get lower by declaring an emergency and making a turn to 010 degrees and descending to FL330. We did so and advised center as soon as we could get a word in on the crowded frequency. Aircraft accelerated to normal airspeed and no further problem was encountered. Prior to departure, additional fuel and extra passenger from a canceled flight were boarded. Our dispatch release was amended via ACARS, but no hard copy of the amended release nor no new flight plan was delivered to the cockpit. The additional weight of fuel and passenger made the aircraft slightly too heavy for cruise at FL350. Since it climbed normally to FL350 and airspeed/altitude were maintained upon leveloff, no problem was initially noted. When the airspeed began to bleed off after a shallow turn, it became obvious we were too heavy for FL350. Prevention: better situational awareness of problem created by additional gross weight. Making sure that if gross weight is increased prior to takeoff a new/amended release and flight plan are delivered to cockpit and reviewed by crew. Better communication between dispatch and the crew when such changes occur after the initial paperwork is issued.

Related reports:

Google
 

Original NASA ASRS Text

Title: DC9 TOO HVY FOR ALT. CREW DECLARES AN EMER AND TURNS OFF TRACK TO DSND IN ZID AIRSPACE.

Narrative: AFTER CLBING TO FL350 AND BEING LEVEL FOR SOME TIME, THE FO (PF) NOTICED THAT FOLLOWING A SHALLOW TURN THE ACFT WAS SLOWLY LOSING AIRSPD. WE SET MAX CONTINUOUS THRUST (MCT), BUT IT APPEARED THAT THE AIRSPD LOSS COULD NOT BE STOPPED. I NOTIFIED CTR THAT WE WOULD REQUIRE A LOWER ALT. CTR SAID WE COULD ONLY GET LOWER BY DECLARING AN EMER AND MAKING A TURN TO 010 DEGS AND DSNDING TO FL330. WE DID SO AND ADVISED CTR AS SOON AS WE COULD GET A WORD IN ON THE CROWDED FREQ. ACFT ACCELERATED TO NORMAL AIRSPD AND NO FURTHER PROB WAS ENCOUNTERED. PRIOR TO DEP, ADDITIONAL FUEL AND EXTRA PAX FROM A CANCELED FLT WERE BOARDED. OUR DISPATCH RELEASE WAS AMENDED VIA ACARS, BUT NO HARD COPY OF THE AMENDED RELEASE NOR NO NEW FLT PLAN WAS DELIVERED TO THE COCKPIT. THE ADDITIONAL WT OF FUEL AND PAX MADE THE ACFT SLIGHTLY TOO HVY FOR CRUISE AT FL350. SINCE IT CLBED NORMALLY TO FL350 AND AIRSPD/ALT WERE MAINTAINED UPON LEVELOFF, NO PROB WAS INITIALLY NOTED. WHEN THE AIRSPD BEGAN TO BLEED OFF AFTER A SHALLOW TURN, IT BECAME OBVIOUS WE WERE TOO HVY FOR FL350. PREVENTION: BETTER SITUATIONAL AWARENESS OF PROB CREATED BY ADDITIONAL GROSS WT. MAKING SURE THAT IF GROSS WT IS INCREASED PRIOR TO TKOF A NEW/AMENDED RELEASE AND FLT PLAN ARE DELIVERED TO COCKPIT AND REVIEWED BY CREW. BETTER COM BTWN DISPATCH AND THE CREW WHEN SUCH CHANGES OCCUR AFTER THE INITIAL PAPERWORK IS ISSUED.

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.