Narrative:

After takeoff out of nrt, abnormal vibration after gear retracted. Felt throughout aircraft but mostly location of doors 3L&right. Aircraft previously written up and inspected for wheel vibration suspected, or tires out of balance, or brakes (in-flight) not slowing gyroscopic tire momentum. Tires, brakes changed, all write-ups cleared in logbook. During climb with vibration, all engine parameters in normal ranges but noted #2 engine egt, N1 N2 slightly higher than other engines. Reduced EPR on #2 engine as power EPR reduced to 1.12 vibration went away when #2 engine advanced forward to normal range with other engines, abnormal vibration recurred. Reduced #2 engine thrust, vibration ceased again. Continued to operate engine #2 at reduced power. Coordinated with company dispatch and maintenance over radios. Advised of problem, and told them previous write-ups had suspected wheels problems but all our indications showed a possible indicated impending engine failure from something internal to engine. Operated engine at reduced thrust and coordinated return to nrt airport. Flight originally routed nrt-sfo., returned to origin airport. Kept engine operating, all other parameters normal. Did not declare emergency. Reduced weight through normal fuel usage -- was not necessary to dump fuel. Landed under maximum landing weight. Made precautionary landing nrt. Normal landing and rollout. Returned to gate and deplaned passenger. Wrote up engine problem in logbook and advised maintenance. Supplemental information from acn 451593: upon company's concurrence, we returned to nrt. No fuel was dumped due to normal burn -- approximately 4 hours. Passenger were deplaned and put on another flight to sfo.

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Original NASA ASRS Text

Title: A B747 IS MANDATED TO RETURN LAND AFTER THE CREW DETERMINES THAT THE SOURCE OF INFLT VIBRATION WAS THE #2 ENG, NOT THE WHEEL VIBRATION AS PREVIOUSLY WRITTEN UP IN THE LOGBOOK. RJAA, NRT, FO.

Narrative: AFTER TKOF OUT OF NRT, ABNORMAL VIBRATION AFTER GEAR RETRACTED. FELT THROUGHOUT ACFT BUT MOSTLY LOCATION OF DOORS 3L&R. ACFT PREVIOUSLY WRITTEN UP AND INSPECTED FOR WHEEL VIBRATION SUSPECTED, OR TIRES OUT OF BAL, OR BRAKES (INFLT) NOT SLOWING GYROSCOPIC TIRE MOMENTUM. TIRES, BRAKES CHANGED, ALL WRITE-UPS CLRED IN LOGBOOK. DURING CLB WITH VIBRATION, ALL ENG PARAMETERS IN NORMAL RANGES BUT NOTED #2 ENG EGT, N1 N2 SLIGHTLY HIGHER THAN OTHER ENGS. REDUCED EPR ON #2 ENG AS PWR EPR REDUCED TO 1.12 VIBRATION WENT AWAY WHEN #2 ENG ADVANCED FORWARD TO NORMAL RANGE WITH OTHER ENGS, ABNORMAL VIBRATION RECURRED. REDUCED #2 ENG THRUST, VIBRATION CEASED AGAIN. CONTINUED TO OPERATE ENG #2 AT REDUCED PWR. COORDINATED WITH COMPANY DISPATCH AND MAINT OVER RADIOS. ADVISED OF PROB, AND TOLD THEM PREVIOUS WRITE-UPS HAD SUSPECTED WHEELS PROBS BUT ALL OUR INDICATIONS SHOWED A POSSIBLE INDICATED IMPENDING ENG FAILURE FROM SOMETHING INTERNAL TO ENG. OPERATED ENG AT REDUCED THRUST AND COORDINATED RETURN TO NRT ARPT. FLT ORIGINALLY ROUTED NRT-SFO., RETURNED TO ORIGIN ARPT. KEPT ENG OPERATING, ALL OTHER PARAMETERS NORMAL. DID NOT DECLARE EMER. REDUCED WT THROUGH NORMAL FUEL USAGE -- WAS NOT NECESSARY TO DUMP FUEL. LANDED UNDER MAX LNDG WT. MADE PRECAUTIONARY LNDG NRT. NORMAL LNDG AND ROLLOUT. RETURNED TO GATE AND DEPLANED PAX. WROTE UP ENG PROB IN LOGBOOK AND ADVISED MAINT. SUPPLEMENTAL INFO FROM ACN 451593: UPON COMPANY'S CONCURRENCE, WE RETURNED TO NRT. NO FUEL WAS DUMPED DUE TO NORMAL BURN -- APPROX 4 HRS. PAX WERE DEPLANED AND PUT ON ANOTHER FLT TO SFO.

Data retrieved from NASA's ASRS site as of July 2007 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.