A B757-200 ON APCH TO EGE EXPERIENCED EXCESSIVE ENG VIBRATION AND UNSTABILIZED APCH DUE TO HVY ICING AND ENG ICE INGESTION.

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DURING FLT XXX SFO TO EGE ON FEB/XA/00; WE ENCOUNTERED AN INTERESTING ICING SIT. ACFT XYZ BEGAN ITS DSCNT FROM RLG IN THE CLR BUT IMMEDIATELY ENTERED THE CLOUDS AND ENCOUNTERED UNANNOUNCED HVY ICING. ENG HEAT WAS ON FROM THE START. AS WE MADE THE TURN AT TALIA AND STARTED DOWN THE VNAV PATH; THE R ENG BEGAN TO SHAKE AND WE NOTED THE ENG VIBRATION INDICATION IN THE YELLOW CAUTION RANGE. WHILE VARYING THE PWR SETTINGS ON THE R ENG IN AN ATTEMPT TO CLR THE ENG AND REDUCE THE VIBRATION THERE WERE CHUG-CHUG SOUNDS; WHICH WE ASSUMED WERE THE RESULTS OF THE ENG INGESTING ICE. SINCE THIS PROCESS WAS DISTRACTING AND THREATENING TO DESTABILIZE THE APCH; WE ELECTED TO GO AROUND (CLR THE ENG) AND REINITIATE THE APCH. ONCE WE CLBED CLR; WE REFERRED TO THE B757 ENG VIBRATION PAGE IN THE OPS BOOK. THE ENG SEEMED TO HAVE CLRED DURING THE GAR AND NOW SEEMED NORMAL. WHILE MANEUVERING FOR ANOTHER APCH; DEN SAID EGE WAS BELOW LIMITS. EGE TWR CONFIRMED 1 1/2 MI VISIBILITY WITH NO CHANCE OF GETTING IN; SO WE WENT TO DEN. ACFT OPS NORMAL AND DEN MAINT MET US AFTER LNDG. POSTFLT INSPECTION REVEALED ICE ON LEADING EDGE VERT STABILIZER NOSE. MAINT BROUGHT US ICE CONES FROM THE ENG BULLETS. WE WILL CHK ENGS. WE FLEW SAME ACFT BACK TO EGE NEXT MORNING -- NO PROBS. TOLD OUTBOUND CAPT OF OUR EXPERIENCE AND HE WAS CONCERNED DUE TO NO LOGBOOK ENTRY. WE ASSURED HIM THAT DEN CHKED IT OUT BUT; IN RETROSPECT; I FEEL I SHOULD HAVE WRITTEN IT UP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT ENCOUNTERED A VERY HVY ICING CONDITION AND WAS CAUSING EXCESSIVE ENG VIBRATIONS INDICATING IN THE YELLOW BAND ON THE ENG VIBRATION INDICATORS. THE RPTR SAID SINCE THE AIRPLANE WAS ON THE APCH AND VARYING THE ENG PWR THE APCH BECAME UNSTABILIZED AND THE DECISION WAS MADE TO GO AROUND. THE RPTR STATED IT IS NOT A COMMON PROB ON THE RB211 ENGS TO DISPLAY VIBRATION WHEN IN ICING CONDITIONS.