RETURN LAND MANDATED AFTER POSSIBLE FOREIGN OBJECT INGESTION DAMAGE ICE IS MADE APPARENT.

Narrative

I ARRIVED AT THE ACFT 50-55 MINS PRIOR TO TKOF TO DO THE PREFLT INSPECTION. AFTER COMPLETING THE INTERIOR PREFLT IN THE COCKPIT; I WALKED TO THE AFT OF THE ACFT TO COMPLETE THAT PORTION OF THE PREFLT. IN CHKING THE WINGS FOR ANY ICE/SNOW/FROST FROM INSIDE THE CABIN AT THE EXIT ROWS; I SAW THAT THERE DID NOT APPEAR TO BE ANY ICE/SNOW OR FROST. THE WINGS LOOKED CLR AND SHINY TO ME. I THEN PROCEEDED OUTSIDE TO PERFORM MY EXTERIOR INSPECTION. I FOUND THE RAMP TO BE WET (DAMP) BUT I DON'T RECALL THAT THERE WAS ANY RAIN FALLING (THE ATIS RPTED 35 DEGS; LIGHT RAIN WITH 5 MI VISIBILITY). I NOTICED THAT DEICING/ANTI- ICING FLUID WAS DRIPPING FROM THE WING SURFACES. THIS INDICATED TO ME THAT THE AIRPLANE HAD BEEN DEICED/ANTI- ICED BY MAINT AND I KNEW THAT; ACCORDING TO MY OPS MANUAL; THAT WHEN ACFT ARE DEICED/ANTI-ICED; THAT THE DEICING/ANTI-ICING CREWS PERFORM A POST DEICING/ANTI- ICING CHK. MY EXTERIOR WALKAROUND DID NOT INDICATE ANY PRESENCE OF ICE/FROST OR SNOW. THIS ALSO INCLUDED THE UNDERSIDE OF BOTH WINGS; WHICH I FOUND TO BE WET -- BUT NO INDICATION OF FROST OR ICE. I RETURNED TO THE CABIN TO CONTINUE TO PREPARE FOR FLT. I ADVISED THE CAPT THAT THE ACFT HAD BEEN DE-ICED AND THAT I DID NOT SEE ANY ICE ON THE ACFT. OUR PUSHBACK AND ENG START WAS NORMAL. I DID NOT HAVE THE INTERPHONE SWITCH TOGGLED UP AT ALL TIMES AS I WAS TALKING WITH GND CTL AND COMPANY ON THE 2 VHF RADIOS; SO I DID NOT HEAR ALL THE INTERPHONE TFC BTWN THE CAPT AND THE GND CREW. THE CAPT TURNED ENG ANTI-ICE ON FOR TAXI. I DO NOT RECALL IF THERE WAS VISIBLE PRECIPITATION DURING OUR TAXI OUT; BUT THE WINDSHIELD WIPERS WERE NOT USED. IT WAS MY TKOF AND ALL INDICATIONS WERE NORMAL. SHORTLY AFTER TKOF; THE CABIN CREW RPTED TO THE CAPT BY INTERPHONE THAT THEY HAD HEARD A BANG (I HAD NO COM DIRECTLY WITH THE CABIN CREW -- I WAS FLYING THE ACFT). ALL ENG INSTS WERE NORMAL AND THERE WAS NO VIBRATION IN THE THROTTLES. AT APPROX 18000 FT; A SLIGHT SPLIT IN THE EPR'S BEGAN TO APPEAR; WHICH BECAME AS HIGH AS A .08 SPLIT. AT APPROX 25000 THE R ENG SURGED AND A NOTICEABLE JOLT WAS FELT (THIS WAS THE FIRST INDICATION TO BE REFLECTED ON THE ENG INSTS) AND THE ENG INSTS REFLECTED ABNORMALITIES. A RETURN TO SEA WAS COORDINATED. AFTER THE R THROTTLE HAD BEEN RETARDED TO A LOWER EPR; THE ENG OPERATED NORMALLY AT THE REDUCED EPR SETTING AND ALL ENG INDICATIONS WERE NORMAL. AN UNEVENTFUL RETURN AND LNDG WAS ACCOMPLISHED. THERE IS SOME SPECULATION THAT THERE MAY HAVE BEEN ICE INGESTION INTO THE R ENG. SUPPLEMENTAL INFO FROM ACN 264653: I ASKED THE COPLT HOW THE WINGS LOOKED. THE FO STATED THE WINGS WERE DRY AND CLEAN ON THE BOTTOM; AND THE WINGS HAD BEEN DE-ICED. IT IS SOP IN SEA FOR MAINT PERSONNEL TO DEICE AND DO THE UPPER WING ICE CHK. THE CAPT OF FLT COULD NOT REMEMBER IF THE UPPER WING ICE CHK WAS COMPLETED PRIOR TO PUSHBACK. AFTER ENG START; ENG ANTI-ICE WAS INITIATED. DURING CLBOUT AT APPROX 1000 AGL; THE FLT ATTENDANT IN JUMPSEAT C RANG THE COCKPIT THROUGH THE INTERPHONE AND SAID SHE HEARD A LOUD BANG. THE COPLT AND I CHKED THE ENG GAUGES. EVERYTHING WAS NORMAL. AT APPROX 8000 FT; I SENT (JUMPSEAT RIDER) FROM XYZ AIRLINE; AN MD-80 COPLT; BACK TO INVESTIGATE. THROUGH THE INTERPHONE HE SAID THE ENGS WERE OUT OF SYNC. I MATCHED UP N1'S AND HE SAID IT SOUNDED MUCH BETTER AND WAS OK. AT 17000 FT; I CALLED SEA MAINT TO NOTIFY THEM EPR GAUGES WERE STARTING TO SPLIT. IT WAS RPTED FROM A MECH THE R ENG SUSTAINED FOREIGN OBJECT DAMAGE FROM ICE INGESTION. THE PROPER PROCEDURES MAY HAVE NOT BEEN FOLLOWED.