Narrative:

We were en route to ZZZ at FL400 near ZZZ1 and on a dispatch planned WX deviation route which was being flown by numerous aircraft. Optimum altitude was FL400 or higher with an airspeed envelope of about 40 KTS. ATC reported rides lower were worse. The flight attendants had been seated for some time due to reports of light to moderate chop en route and our proximity to WX areas. Seatbelt sign was on and I had warned the passenger 2 or 3 times starting before pushback that there was significant WX near our route and that 'the seatbelt sign is not a suggestion tonight. If it is on; we insist you remain buckled in your seats.' we deviated farther north from the radar echoes; so as to clear the nearest storms horizontally by at least 40 NM. Another aircraft 100 NM northwest reported moderate turbulence. This was the only other significant report beyond light to moderate turbulence. Soon after passing west of the first radar echoes we encountered occasional moderate turbulence; which quickly increased to moderate to severe; then severe turbulence. Airspeed oscillated between .76 and .79 mach with a brief mmo exceedance (1 - 1.5 seconds) to .81 mach; as the airspeed did not respond to power reduction. Roll oscillations were +15 degrees from horizontal and the aircraft was somewhat unresponsive to control inputs. We requested and were immediately cleared to FL360. Once we were able to control airspeed enough to descend; we left the severe turbulence layer out of FL385 and encountered light to moderate chop down to and including FL360. We were in severe turbulence for 2-3 mins. I queried the passenger and flight attendants and they reported everyone was seated during the event and no one had been injured. We reported the encounter to dispatch who coordination maintenance upon arrival at ZZZ. All system were normal for the duration of the flight. Made entries in aircraft logbook and met maintenance in ZZZ. Other than awaiting better turbulence detection technology; I cannot think of any way this could have been avoided. I would emphasize that crews should be trained to make emphatic passenger announcements when the ride could be rough and to flight attendants; that they must remain seated when directed; even if it seems it will be smooth.

Related reports:

Google
 

Original NASA ASRS Text

Title: A B737-700 ENCOUNTERED SEVERE TURBULENCE AT FL400 WITH CREW AND PAX SEATED. THE ACFT EXCEEDED MMO AND REQUIRED A POST FLT INSPECTION.

Narrative: WE WERE ENRTE TO ZZZ AT FL400 NEAR ZZZ1 AND ON A DISPATCH PLANNED WX DEV RTE WHICH WAS BEING FLOWN BY NUMEROUS ACFT. OPTIMUM ALT WAS FL400 OR HIGHER WITH AN AIRSPD ENVELOPE OF ABOUT 40 KTS. ATC RPTED RIDES LOWER WERE WORSE. THE FLT ATTENDANTS HAD BEEN SEATED FOR SOME TIME DUE TO RPTS OF LIGHT TO MODERATE CHOP ENRTE AND OUR PROX TO WX AREAS. SEATBELT SIGN WAS ON AND I HAD WARNED THE PAX 2 OR 3 TIMES STARTING BEFORE PUSHBACK THAT THERE WAS SIGNIFICANT WX NEAR OUR RTE AND THAT 'THE SEATBELT SIGN IS NOT A SUGGESTION TONIGHT. IF IT IS ON; WE INSIST YOU REMAIN BUCKLED IN YOUR SEATS.' WE DEVIATED FARTHER N FROM THE RADAR ECHOES; SO AS TO CLR THE NEAREST STORMS HORIZONTALLY BY AT LEAST 40 NM. ANOTHER ACFT 100 NM NW RPTED MODERATE TURB. THIS WAS THE ONLY OTHER SIGNIFICANT RPT BEYOND LIGHT TO MODERATE TURB. SOON AFTER PASSING W OF THE FIRST RADAR ECHOES WE ENCOUNTERED OCCASIONAL MODERATE TURB; WHICH QUICKLY INCREASED TO MODERATE TO SEVERE; THEN SEVERE TURB. AIRSPD OSCILLATED BTWN .76 AND .79 MACH WITH A BRIEF MMO EXCEEDANCE (1 - 1.5 SECONDS) TO .81 MACH; AS THE AIRSPD DID NOT RESPOND TO PWR REDUCTION. ROLL OSCILLATIONS WERE +15 DEGS FROM HORIZ AND THE ACFT WAS SOMEWHAT UNRESPONSIVE TO CTL INPUTS. WE REQUESTED AND WERE IMMEDIATELY CLRED TO FL360. ONCE WE WERE ABLE TO CTL AIRSPD ENOUGH TO DSND; WE LEFT THE SEVERE TURB LAYER OUT OF FL385 AND ENCOUNTERED LIGHT TO MODERATE CHOP DOWN TO AND INCLUDING FL360. WE WERE IN SEVERE TURB FOR 2-3 MINS. I QUERIED THE PAX AND FLT ATTENDANTS AND THEY RPTED EVERYONE WAS SEATED DURING THE EVENT AND NO ONE HAD BEEN INJURED. WE RPTED THE ENCOUNTER TO DISPATCH WHO COORD MAINT UPON ARR AT ZZZ. ALL SYS WERE NORMAL FOR THE DURATION OF THE FLT. MADE ENTRIES IN ACFT LOGBOOK AND MET MAINT IN ZZZ. OTHER THAN AWAITING BETTER TURB DETECTION TECHNOLOGY; I CANNOT THINK OF ANY WAY THIS COULD HAVE BEEN AVOIDED. I WOULD EMPHASIZE THAT CREWS SHOULD BE TRAINED TO MAKE EMPHATIC PAX ANNOUNCEMENTS WHEN THE RIDE COULD BE ROUGH AND TO FLT ATTENDANTS; THAT THEY MUST REMAIN SEATED WHEN DIRECTED; EVEN IF IT SEEMS IT WILL BE SMOOTH.

Data retrieved from NASA's ASRS site as of May 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.