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.