AN MD80 CAPT RPTED THAT HE AND HIS FO DID NOT RECOGNIZE THE ACFT'S STALLED ATTITUDE.

Narrative

PRIOR TO DEP A BAGGAGE CART HIT THE R WING. NO REAL VISIBLE DAMAGE WAS NOTICED. MAINT INSPECTED AND SIGNED THE BOOK OFF. THE FLT PLAN HAD US GOING TO FL330. WHILE AT FL330; ABOUT 1 HR INTO THE FLT; JUST PAST BCE; WE WERE DEVIATING AROUND SOME LARGE CELLS. OCCASIONAL LIGHT CHOP. SEATBELT SIGN ON. ACFT ENG AND WING ANTI-ICE ON AS WE HAD JUST COME THROUGH A CLOUD LAYER. ACFT WT 129000 LBS. THE DEVS AND CONVECTIVE ACTIVITY DID NOT SEEM TO BE ANYTHING UNUSUAL. WE STARTED TO FEEL A BUFFET AND RUMBLE. HAVING NOT FELT THAT BEFORE; AND NOT BEING CLOSE TO OUR MAX WT FOR THE ALT; THE FO AND I THOUGHT IT WAS A STRUCTURAL PROB; MAYBE A PROB WITH THE R WING. AS THE BUFFETING THE RUMBLE GOT WORSE THE ACFT WAS HAVING A HARD TIME MAINTAINING ALT AND WINGS LEVEL. THE FO KICKED OFF THE AUTOPLT AND AUTOTHROTTLES. I TOLD HER TO 'LET THE PLANE COME DOWN.' SHE LOWERED THE NOSE AND I CALLED ATC TO DECLARE AN EMER AND ASK ABOUT A SUITABLE PLACE TO LAND. AS THE PLANE WAS COMING THROUGH ABOUT FL330 I TOOK THE PLANE FROM THE FO. I ADDED SOME MORE PWR; RETRIMMED THE ACFT; AND LEVELED AT FL290. I WAS STILL HAND-FLYING THE PLANE AND IT WAS FLYING FINE. I THEN THOUGHT THE PROB WAS NOT STRUCTURAL AND THAT WE HAD APCHED A STALL. I GAVE THE PLANE BACK TO THE FO; MADE A PA; AND CALLED DISPATCH. AT NO TIME WERE THE ENGS CLOSE TO BEING OVER-BOOSTED. WE FOUND OUT LATER THAT THERE WAS MOUNTAIN WAVE ACTIVITY IN THE AREA. I THINK A COMBINATION OF MOUNTAIN WAVE; LACK OF PWR FROM ACFT ENG AND WING ANTI-ICE; AND POSSIBLE SLOW OR NO RESPONSE FROM THE AUTOTHROTTLES; CONTRIBUTED TO THIS EVENT.