Narrative:

Cruising along; began to lose power on right engine. Our route with minor deviations had until this point kept us clear of all WX and clouds. We noticed WX activity around the mountains to the west of us. Earlier in the flight we established communication with another flight proceeding along part of our route about 10 mins ahead of us. Later; we were close enough to hear the xmissions. Performance of our HF radios marginal this night. Outside of reading the engine gauges there were no EICAS or status messages to indicate what type of engine problem might be occurring. Right engine EPR pegged high egt hung at 670 degrees C matched seis indicator. N1; N2; N3; ff all decreasing. Turned off the autothrottles. Turning on the right engine anti-ice caused a heavy vibration in the rudder pedals and flight deck floor. Not sure at the time just where we could have picked up any ice; we thought the vibration might be ice shedding. We took many things into consideration including fuel contamination. As our airspeed began to decrease; I directed the first officer to request from control descent to FL310. Control initially denied our request with an unable request for FL310 response. At this point we had slowed from mach .81 decelerating through mach .77. I directed the first officer to declare an emergency with mayday X3. With our new status; control gave us clearance immediately to FL310 without reference to any conflicting air traffic. Once level at FL310 after about 4 mins; the right engine power stabilized at a reasonable power setting. However; we still had vibration in the flight deck floor boards and rudder peddles with no additional supporting indications from our engine instruments. The vibration monitor of the right engine continuously showed N1 vibration level 1.3. Still in clear air; we decided the right engine should have been well cleared of any ice and we shut the engine anti-ice off. The vibration went away. Turning the engine anti-ice back on brought the hull vibration back. The first officer and I concluded the bleed off of the right engine for anti-ice was somehow disturbing the normal flow of air through the engine causing vibration. Other company flts made patches to dispatch. Between these 2 aircraft we were able to get information to and from dispatch and maintenance. According to maintenance; our aircraft had a history with loss of engine power on the right engine FL350 and above. In all cases; the right engine stabilized with a reasonable power setting at a lower than FL350 cruise altitude. Dispatch outlined numerous diversion airports where we had parts and operations. The relief pilot monitored the nearest emergency airports in case a landing as soon as possible should become necessary. With all the information; heavy weight; WX and possibility no right engine; no right engine anti-ice; engine history and for the time being stabilized power on the right engine. I elected to maintain FL310; stay away from WX; mountainous terrain including our planned destination. And divert.

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Original NASA ASRS Text

Title: B757-200 FLT CREW HAS LOSS OF PWR IN THE R ENG DURING CRUISE FLT AT FL350.

Narrative: CRUISING ALONG; BEGAN TO LOSE PWR ON R ENG. OUR RTE WITH MINOR DEVS HAD UNTIL THIS POINT KEPT US CLR OF ALL WX AND CLOUDS. WE NOTICED WX ACTIVITY AROUND THE MOUNTAINS TO THE W OF US. EARLIER IN THE FLT WE ESTABLISHED COM WITH ANOTHER FLT PROCEEDING ALONG PART OF OUR RTE ABOUT 10 MINS AHEAD OF US. LATER; WE WERE CLOSE ENOUGH TO HEAR THE XMISSIONS. PERFORMANCE OF OUR HF RADIOS MARGINAL THIS NIGHT. OUTSIDE OF READING THE ENG GAUGES THERE WERE NO EICAS OR STATUS MESSAGES TO INDICATE WHAT TYPE OF ENG PROB MIGHT BE OCCURRING. R ENG EPR PEGGED HIGH EGT HUNG AT 670 DEGS C MATCHED SEIS INDICATOR. N1; N2; N3; FF ALL DECREASING. TURNED OFF THE AUTOTHROTTLES. TURNING ON THE R ENG ANTI-ICE CAUSED A HVY VIBRATION IN THE RUDDER PEDALS AND FLT DECK FLOOR. NOT SURE AT THE TIME JUST WHERE WE COULD HAVE PICKED UP ANY ICE; WE THOUGHT THE VIBRATION MIGHT BE ICE SHEDDING. WE TOOK MANY THINGS INTO CONSIDERATION INCLUDING FUEL CONTAMINATION. AS OUR AIRSPD BEGAN TO DECREASE; I DIRECTED THE FO TO REQUEST FROM CTL DESCENT TO FL310. CTL INITIALLY DENIED OUR REQUEST WITH AN UNABLE REQUEST FOR FL310 RESPONSE. AT THIS POINT WE HAD SLOWED FROM MACH .81 DECELERATING THROUGH MACH .77. I DIRECTED THE FO TO DECLARE AN EMER WITH MAYDAY X3. WITH OUR NEW STATUS; CTL GAVE US CLRNC IMMEDIATELY TO FL310 WITHOUT REF TO ANY CONFLICTING AIR TFC. ONCE LEVEL AT FL310 AFTER ABOUT 4 MINS; THE R ENG PWR STABILIZED AT A REASONABLE PWR SETTING. HOWEVER; WE STILL HAD VIBRATION IN THE FLT DECK FLOOR BOARDS AND RUDDER PEDDLES WITH NO ADDITIONAL SUPPORTING INDICATIONS FROM OUR ENG INSTS. THE VIBRATION MONITOR OF THE R ENG CONTINUOUSLY SHOWED N1 VIBRATION LEVEL 1.3. STILL IN CLR AIR; WE DECIDED THE R ENG SHOULD HAVE BEEN WELL CLRED OF ANY ICE AND WE SHUT THE ENG ANTI-ICE OFF. THE VIBRATION WENT AWAY. TURNING THE ENG ANTI-ICE BACK ON BROUGHT THE HULL VIBRATION BACK. THE FO AND I CONCLUDED THE BLEED OFF OF THE R ENG FOR ANTI-ICE WAS SOMEHOW DISTURBING THE NORMAL FLOW OF AIR THROUGH THE ENG CAUSING VIBRATION. OTHER COMPANY FLTS MADE PATCHES TO DISPATCH. BTWN THESE 2 ACFT WE WERE ABLE TO GET INFO TO AND FROM DISPATCH AND MAINT. ACCORDING TO MAINT; OUR ACFT HAD A HISTORY WITH LOSS OF ENG PWR ON THE R ENG FL350 AND ABOVE. IN ALL CASES; THE R ENG STABILIZED WITH A REASONABLE PWR SETTING AT A LOWER THAN FL350 CRUISE ALT. DISPATCH OUTLINED NUMEROUS DIVERSION ARPTS WHERE WE HAD PARTS AND OPS. THE RELIEF PLT MONITORED THE NEAREST EMER ARPTS IN CASE A LNDG ASAP SHOULD BECOME NECESSARY. WITH ALL THE INFO; HVY WT; WX AND POSSIBILITY NO R ENG; NO R ENG ANTI-ICE; ENG HISTORY AND FOR THE TIME BEING STABILIZED PWR ON THE R ENG. I ELECTED TO MAINTAIN FL310; STAY AWAY FROM WX; MOUNTAINOUS TERRAIN INCLUDING OUR PLANNED DEST. AND DIVERT.

Data retrieved from NASA's ASRS site as of January 2009 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.