Narrative:

The following report is in reference to flight from narita, japan, to singapore (nrt-sin). At preflight in the narita flight dispatch office, I was given an upper air depiction chart which showed a takeoff line our flight would transit with the remarks to expect code 1-2 turbulence. The surface depiction chart for our flight showed no significant WX. The upper level tp's showed tp AI11 indicating light to moderate turbulence in an area east of our track (A-590). Also noted was a PIREP of severe turbulence over temar intersection which was approximately 50 NM east of our track. The briefing dispatcher said to expect some brief light turbulence and that the reported severe turbulence was old and of no concern. We climbed to FL350 instead of the planned flight level of FL390 because I felt we were too close to the maximum weight for the altitude. At bubdo intersection we began experiencing what we reported as turbulence. Shortly afterwards, aircraft XXX reported moderate to severe at FL390 (same airway, 5 mins ahead of us). Based on that report, I called the lead flight attendant and advised to put away all serving carts and have all flight attendants be seated. I neglected to record progress on the flight plan as we were communicating with tokyo control and were quite busy dealing with the turbulence, but I believe in our estimation of moderate to severe turbulence over dovag, bixak, and md intxns we reported code 5 turbulence. The entire time in turbulence we used the autoplt in 'turbulence' mode with the first officer maintaining speed with the throttles and myself maintaining altitude and course with the manual pitch and roll controllers. We, as a crew, believed that movement about the cabin would have resulted in injuries! 2 flight numbers I remember reporting 'moderate to severe' were XXX and YYY. There were others reporting the turbulence, but I don't recall the flight designations. At one point, we were advised that there was a SIGMET #2 for our area of flight calling for 'severe' turbulence. In querying our dispatch, they responded that they had no reports beyond moderate turbulence. In fact, sigmets #1, #2, #3, and #4 had been issued and all mentioning the severe turbulence. 3 days later I procured copies of the above. Upon landing in singapore, I was asked by maintenance control if I would consider changing the reports to moderate as 'pilots often overstated turbulence,' and they referred me to fom. I regret that person wasn't in the back of that aircraft during that flight event! Upon arriving at the layover hotel, I was called by air carrier maintenance control, who was in contact with our mc, and I was asked if I would add to the logbook write-up 'captain requests severe turbulence check.' I refused that request in that I had no directive to do such in any flight manual that has been issued to me. After the fact, I find that the boeing maintenance manuals calls for the captain to request a severe turbulence check.

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Original NASA ASRS Text

Title: A B747 EXPERIENCED SEVERE TURB AT FL350 NEAR NRT.

Narrative: THE FOLLOWING RPT IS IN REF TO FLT FROM NARITA, JAPAN, TO SINGAPORE (NRT-SIN). AT PREFLT IN THE NARITA FLT DISPATCH OFFICE, I WAS GIVEN AN UPPER AIR DEPICTION CHART WHICH SHOWED A TKOF LINE OUR FLT WOULD TRANSIT WITH THE REMARKS TO EXPECT CODE 1-2 TURB. THE SURFACE DEPICTION CHART FOR OUR FLT SHOWED NO SIGNIFICANT WX. THE UPPER LEVEL TP'S SHOWED TP AI11 INDICATING LIGHT TO MODERATE TURB IN AN AREA E OF OUR TRACK (A-590). ALSO NOTED WAS A PIREP OF SEVERE TURB OVER TEMAR INTXN WHICH WAS APPROX 50 NM E OF OUR TRACK. THE BRIEFING DISPATCHER SAID TO EXPECT SOME BRIEF LIGHT TURB AND THAT THE RPTED SEVERE TURB WAS OLD AND OF NO CONCERN. WE CLBED TO FL350 INSTEAD OF THE PLANNED FLT LEVEL OF FL390 BECAUSE I FELT WE WERE TOO CLOSE TO THE MAX WT FOR THE ALT. AT BUBDO INTXN WE BEGAN EXPERIENCING WHAT WE RPTED AS TURB. SHORTLY AFTERWARDS, ACFT XXX RPTED MODERATE TO SEVERE AT FL390 (SAME AIRWAY, 5 MINS AHEAD OF US). BASED ON THAT RPT, I CALLED THE LEAD FLT ATTENDANT AND ADVISED TO PUT AWAY ALL SERVING CARTS AND HAVE ALL FLT ATTENDANTS BE SEATED. I NEGLECTED TO RECORD PROGRESS ON THE FLT PLAN AS WE WERE COMMUNICATING WITH TOKYO CTL AND WERE QUITE BUSY DEALING WITH THE TURB, BUT I BELIEVE IN OUR ESTIMATION OF MODERATE TO SEVERE TURB OVER DOVAG, BIXAK, AND MD INTXNS WE RPTED CODE 5 TURB. THE ENTIRE TIME IN TURB WE USED THE AUTOPLT IN 'TURB' MODE WITH THE FO MAINTAINING SPD WITH THE THROTTLES AND MYSELF MAINTAINING ALT AND COURSE WITH THE MANUAL PITCH AND ROLL CTLRS. WE, AS A CREW, BELIEVED THAT MOVEMENT ABOUT THE CABIN WOULD HAVE RESULTED IN INJURIES! 2 FLT NUMBERS I REMEMBER RPTING 'MODERATE TO SEVERE' WERE XXX AND YYY. THERE WERE OTHERS RPTING THE TURB, BUT I DON'T RECALL THE FLT DESIGNATIONS. AT ONE POINT, WE WERE ADVISED THAT THERE WAS A SIGMET #2 FOR OUR AREA OF FLT CALLING FOR 'SEVERE' TURB. IN QUERYING OUR DISPATCH, THEY RESPONDED THAT THEY HAD NO RPTS BEYOND MODERATE TURB. IN FACT, SIGMETS #1, #2, #3, AND #4 HAD BEEN ISSUED AND ALL MENTIONING THE SEVERE TURB. 3 DAYS LATER I PROCURED COPIES OF THE ABOVE. UPON LNDG IN SINGAPORE, I WAS ASKED BY MAINT CTL IF I WOULD CONSIDER CHANGING THE RPTS TO MODERATE AS 'PLTS OFTEN OVERSTATED TURB,' AND THEY REFERRED ME TO FOM. I REGRET THAT PERSON WASN'T IN THE BACK OF THAT ACFT DURING THAT FLT EVENT! UPON ARRIVING AT THE LAYOVER HOTEL, I WAS CALLED BY ACR MAINT CTL, WHO WAS IN CONTACT WITH OUR MC, AND I WAS ASKED IF I WOULD ADD TO THE LOGBOOK WRITE-UP 'CAPT REQUESTS SEVERE TURB CHK.' I REFUSED THAT REQUEST IN THAT I HAD NO DIRECTIVE TO DO SUCH IN ANY FLT MANUAL THAT HAS BEEN ISSUED TO ME. AFTER THE FACT, I FIND THAT THE BOEING MAINT MANUALS CALLS FOR THE CAPT TO REQUEST A SEVERE TURB CHK.

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.