Narrative:

Incident report at nbo airport, resulting in return for landing may/fri/02. Crew members on board: captain was PF, first officer in right seat PNF. One first officer was jump seat support pilot, another first officer jump seat support pilot. All takeoff preparations were completed up to final flight deck procedure. We inputted ZFW data as per fom into the FMS. The zero fuel weight was 270.2 tons and fuel on board 108.2. Tons. Completed pushback and taxi. All checklists complete. Normal maximum thrust departure on the narok B SID runway 6 to FL310. Departure speeds as computed by the crew members V1 150, VR167, V2 177. The FMC speeds confirmed and entered at V1 151, vr 168, V2 179. Cleared for takeoff, the engine parameters normal and takeoff normal. On climb out, aircraft was stable at V2 +15 KTS (+/- 1 KT), then noted that target command speed bug accelerated on its own accord to V2 +23 KTS at 300 ft RA. Rest of climb out normal on narok B SID until flap retraction from position 1 to 'up' at approximately 270 KIAS on pfd. Speed indicated approximately flaps up speed and increasing, before calling for flaps retraction. Immediately upon movement of flap to 'up,' stickshaker activated as low and high speed buffet margin merged at rapid rate. Immediately called for maximum thrust and flaps extension back to position 1. Stickshaker ceased. Buffet speed tape separated to within safe margins for flap position. Aircraft climbing in light turbulence in IMC, cumulonimbus in the vicinity, when clear of the WX approximately 3 mins. Repeated flap retraction with same result. No EICAS and no status message displayed. Aircraft at about FL180 climbing intermediate leveloff requested and approved. At FL200 crew in concern researched QRH, performance data and aircraft flight manual. Engineer was summoned to assist in evaluation of situation. Requested return to nbo. En route aircraft stable and autoplt on. A last attempt to retract flaps was made with the same result. Aircraft was cleared to descend to 12000 ft. Due to terrain, stopped descent at 15000 ft. Satcom was established with dispatch and maintenance. We informed them, of our situation to dump fuel and land at nbo in concurrence with dispatch. Flew initially towards gg. Due to WX, elected to hold at nv at 15000 ft. Initiated fuel dump per QRH and declared emergency. During dumping, approximately 40 mins, made numerous attempts to contact operations on satcom unsuccessfully due to phone number being 'not authority/authorized.' due to encroaching cumulonimbus approaching airport and fuel gravity xfer valve problem, resulting in fuel imbal, dumping was terminated and decision to land overweight was made for touchdown at 305.1 tons per FMC weight was made. During dumping, it was discovered that captain's and first officer's pfd indicated airspds were in agreement. However, their information was approximately 15 KTS higher than the standby airspeed indicator. Based on the above information and crew assumption by all available information that we were at a higher weight than predicted, we had a flight computer system problem. A vref speed was manually calculated based on current condition. Landing was accomplished at flaps 30 degrees. Aircraft returned to apron, all checklist procedures accomplished. Aircraft secured, the crew departed to the hotel.

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Original NASA ASRS Text

Title: B747-400 CREW HAD CONTINUOUS STICKSHAKER AND AIRSPD IRREGULARITY ON DEP AT HKJK.

Narrative: INCIDENT RPT AT NBO ARPT, RESULTING IN RETURN FOR LNDG MAY/FRI/02. CREW MEMBERS ON BOARD: CAPT WAS PF, FO IN R SEAT PNF. ONE FO WAS JUMP SEAT SUPPORT PLT, ANOTHER FO JUMP SEAT SUPPORT PLT. ALL TKOF PREPARATIONS WERE COMPLETED UP TO FINAL FLT DECK PROC. WE INPUTTED ZFW DATA AS PER FOM INTO THE FMS. THE ZERO FUEL WT WAS 270.2 TONS AND FUEL ON BOARD 108.2. TONS. COMPLETED PUSHBACK AND TAXI. ALL CHKLISTS COMPLETE. NORMAL MAX THRUST DEP ON THE NAROK B SID RWY 6 TO FL310. DEP SPDS AS COMPUTED BY THE CREW MEMBERS V1 150, VR167, V2 177. THE FMC SPDS CONFIRMED AND ENTERED AT V1 151, VR 168, V2 179. CLRED FOR TKOF, THE ENG PARAMETERS NORMAL AND TKOF NORMAL. ON CLBOUT, ACFT WAS STABLE AT V2 +15 KTS (+/- 1 KT), THEN NOTED THAT TARGET COMMAND SPD BUG ACCELERATED ON ITS OWN ACCORD TO V2 +23 KTS AT 300 FT RA. REST OF CLBOUT NORMAL ON NAROK B SID UNTIL FLAP RETRACTION FROM POS 1 TO 'UP' AT APPROX 270 KIAS ON PFD. SPD INDICATED APPROX FLAPS UP SPD AND INCREASING, BEFORE CALLING FOR FLAPS RETRACTION. IMMEDIATELY UPON MOVEMENT OF FLAP TO 'UP,' STICKSHAKER ACTIVATED AS LOW AND HIGH SPD BUFFET MARGIN MERGED AT RAPID RATE. IMMEDIATELY CALLED FOR MAX THRUST AND FLAPS EXTENSION BACK TO POS 1. STICKSHAKER CEASED. BUFFET SPD TAPE SEPARATED TO WITHIN SAFE MARGINS FOR FLAP POS. ACFT CLBING IN LIGHT TURB IN IMC, CUMULONIMBUS IN THE VICINITY, WHEN CLR OF THE WX APPROX 3 MINS. REPEATED FLAP RETRACTION WITH SAME RESULT. NO EICAS AND NO STATUS MESSAGE DISPLAYED. ACFT AT ABOUT FL180 CLBING INTERMEDIATE LEVELOFF REQUESTED AND APPROVED. AT FL200 CREW IN CONCERN RESEARCHED QRH, PERFORMANCE DATA AND ACFT FLT MANUAL. ENGINEER WAS SUMMONED TO ASSIST IN EVALUATION OF SIT. REQUESTED RETURN TO NBO. ENRTE ACFT STABLE AND AUTOPLT ON. A LAST ATTEMPT TO RETRACT FLAPS WAS MADE WITH THE SAME RESULT. ACFT WAS CLRED TO DSND TO 12000 FT. DUE TO TERRAIN, STOPPED DSCNT AT 15000 FT. SATCOM WAS ESTABLISHED WITH DISPATCH AND MAINT. WE INFORMED THEM, OF OUR SIT TO DUMP FUEL AND LAND AT NBO IN CONCURRENCE WITH DISPATCH. FLEW INITIALLY TOWARDS GG. DUE TO WX, ELECTED TO HOLD AT NV AT 15000 FT. INITIATED FUEL DUMP PER QRH AND DECLARED EMER. DURING DUMPING, APPROX 40 MINS, MADE NUMEROUS ATTEMPTS TO CONTACT OPS ON SATCOM UNSUCCESSFULLY DUE TO PHONE NUMBER BEING 'NOT AUTH.' DUE TO ENCROACHING CUMULONIMBUS APCHING ARPT AND FUEL GRAVITY XFER VALVE PROB, RESULTING IN FUEL IMBAL, DUMPING WAS TERMINATED AND DECISION TO LAND OVERWT WAS MADE FOR TOUCHDOWN AT 305.1 TONS PER FMC WT WAS MADE. DURING DUMPING, IT WAS DISCOVERED THAT CAPT'S AND FO'S PFD INDICATED AIRSPDS WERE IN AGREEMENT. HOWEVER, THEIR INFO WAS APPROX 15 KTS HIGHER THAN THE STANDBY AIRSPD INDICATOR. BASED ON THE ABOVE INFO AND CREW ASSUMPTION BY ALL AVAILABLE INFO THAT WE WERE AT A HIGHER WT THAN PREDICTED, WE HAD A FLT COMPUTER SYS PROB. A VREF SPD WAS MANUALLY CALCULATED BASED ON CURRENT CONDITION. LNDG WAS ACCOMPLISHED AT FLAPS 30 DEGS. ACFT RETURNED TO APRON, ALL CHKLIST PROCS ACCOMPLISHED. ACFT SECURED, THE CREW DEPARTED TO THE HOTEL.

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.