Narrative:

In cruise; flying over an undercast in clear air at FL390. The previous controller had reported occasional moderate turbulence; but when asked if it impacted our route of flight; we were told it didn't. We were flying at the recommended altitude for the best ride and only experienced occasional light chop. We changed frequencys and checked in with the next controller. The seat belt signs were off. Shortly after contacting the new controller; the aircraft encounter a sharp jolt of moderate-plus turbulence lasting for approximately 2 seconds. It felt as if we crossed another aircraft's wake turbulence; but there was no traffic in the area. The aircraft's attitude went from wings-level to about a 20 degree left bank and slight nose pitch-up. As suddenly as it started; it was over and back in occasional light chop. As the encounter began; I switched on the seat belt sign and retarded the throttles to slow the aircraft to maneuvering speed; as well as clicking off the autoplt to level the wings. I slowed the speed to the recommended rough airspeed and reconnected the autoplt. As I reached for the throttles; the first officer grabbed the PA handset to make the 'take your seats' announcement. Later; I learned that when she tried to use the handset; there was a busy signal and she returned to her radio work. Shortly after I reconnected the autoplt; we got a call from the purser. She said there were no injuries and that everyone was seated. I told her for everyone to remain seated. We reported the turbulence to ATC and were told that there were no other reports in the sector. Shortly thereafter; we received a call from the cabin notifying us that there were 3 injured flight attendants in the rear of the aircraft. They were not seriously injured as to require medical assistance in sfo. As a precaution; the purser removed them from their duties. I notified sfo operations of the situation and asked that an supervisor meet the aircraft in sfo. I was asked to phone the dispatcher and the duty manager on arrival. We continued uneventfully to sfo. Upon arrival to sfo; we were met by the supervisor who coordinated with the flight attendants. They were taken to medical for evaluate. I spoke with the dispatcher and the duty manager relating the events. At that time I was met by an FAA safety inspector who was riding in the last row of the aircraft and was able to observe the events. He stated that at the time of the turbulence encounter; there were passenger in the aisle. I was not told of that. The flight attendants shouted commands to take protective position; which the passenger did. The inspector said that shortly afterward; he observed a passenger again standing in the aisle; about to use the restroom. He was concerned because nobody ordered the passenger to be seated. He said that shortly after that; he observed a flight attendant walking in the aisle with a bag of ice for one of the injured flight attendants. That concerned him enough to contact the purser and voice his concerns. She had not heard my instructions from the purser to stay seated. He said that overall; everything was handled adequately; but was concerned that the level of communication in the back cabin was deficient.

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Original NASA ASRS Text

Title: B777 FLT CREW ENCOUNTERS CAT WHILE AT CRUISE.

Narrative: IN CRUISE; FLYING OVER AN UNDERCAST IN CLR AIR AT FL390. THE PREVIOUS CTLR HAD RPTED OCCASIONAL MODERATE TURB; BUT WHEN ASKED IF IT IMPACTED OUR RTE OF FLT; WE WERE TOLD IT DIDN'T. WE WERE FLYING AT THE RECOMMENDED ALT FOR THE BEST RIDE AND ONLY EXPERIENCED OCCASIONAL LIGHT CHOP. WE CHANGED FREQS AND CHKED IN WITH THE NEXT CTLR. THE SEAT BELT SIGNS WERE OFF. SHORTLY AFTER CONTACTING THE NEW CTLR; THE ACFT ENCOUNTER A SHARP JOLT OF MODERATE-PLUS TURB LASTING FOR APPROX 2 SECONDS. IT FELT AS IF WE CROSSED ANOTHER ACFT'S WAKE TURB; BUT THERE WAS NO TFC IN THE AREA. THE ACFT'S ATTITUDE WENT FROM WINGS-LEVEL TO ABOUT A 20 DEG L BANK AND SLIGHT NOSE PITCH-UP. AS SUDDENLY AS IT STARTED; IT WAS OVER AND BACK IN OCCASIONAL LIGHT CHOP. AS THE ENCOUNTER BEGAN; I SWITCHED ON THE SEAT BELT SIGN AND RETARDED THE THROTTLES TO SLOW THE ACFT TO MANEUVERING SPD; AS WELL AS CLICKING OFF THE AUTOPLT TO LEVEL THE WINGS. I SLOWED THE SPD TO THE RECOMMENDED ROUGH AIRSPD AND RECONNECTED THE AUTOPLT. AS I REACHED FOR THE THROTTLES; THE FO GRABBED THE PA HANDSET TO MAKE THE 'TAKE YOUR SEATS' ANNOUNCEMENT. LATER; I LEARNED THAT WHEN SHE TRIED TO USE THE HANDSET; THERE WAS A BUSY SIGNAL AND SHE RETURNED TO HER RADIO WORK. SHORTLY AFTER I RECONNECTED THE AUTOPLT; WE GOT A CALL FROM THE PURSER. SHE SAID THERE WERE NO INJURIES AND THAT EVERYONE WAS SEATED. I TOLD HER FOR EVERYONE TO REMAIN SEATED. WE RPTED THE TURB TO ATC AND WERE TOLD THAT THERE WERE NO OTHER RPTS IN THE SECTOR. SHORTLY THEREAFTER; WE RECEIVED A CALL FROM THE CABIN NOTIFYING US THAT THERE WERE 3 INJURED FLT ATTENDANTS IN THE REAR OF THE ACFT. THEY WERE NOT SERIOUSLY INJURED AS TO REQUIRE MEDICAL ASSISTANCE IN SFO. AS A PRECAUTION; THE PURSER REMOVED THEM FROM THEIR DUTIES. I NOTIFIED SFO OPS OF THE SITUATION AND ASKED THAT AN SUPVR MEET THE ACFT IN SFO. I WAS ASKED TO PHONE THE DISPATCHER AND THE DUTY MGR ON ARR. WE CONTINUED UNEVENTFULLY TO SFO. UPON ARR TO SFO; WE WERE MET BY THE SUPVR WHO COORDINATED WITH THE FLT ATTENDANTS. THEY WERE TAKEN TO MEDICAL FOR EVAL. I SPOKE WITH THE DISPATCHER AND THE DUTY MGR RELATING THE EVENTS. AT THAT TIME I WAS MET BY AN FAA SAFETY INSPECTOR WHO WAS RIDING IN THE LAST ROW OF THE ACFT AND WAS ABLE TO OBSERVE THE EVENTS. HE STATED THAT AT THE TIME OF THE TURB ENCOUNTER; THERE WERE PAX IN THE AISLE. I WAS NOT TOLD OF THAT. THE FLT ATTENDANTS SHOUTED COMMANDS TO TAKE PROTECTIVE POS; WHICH THE PAX DID. THE INSPECTOR SAID THAT SHORTLY AFTERWARD; HE OBSERVED A PAX AGAIN STANDING IN THE AISLE; ABOUT TO USE THE RESTROOM. HE WAS CONCERNED BECAUSE NOBODY ORDERED THE PAX TO BE SEATED. HE SAID THAT SHORTLY AFTER THAT; HE OBSERVED A FLT ATTENDANT WALKING IN THE AISLE WITH A BAG OF ICE FOR ONE OF THE INJURED FLT ATTENDANTS. THAT CONCERNED HIM ENOUGH TO CONTACT THE PURSER AND VOICE HIS CONCERNS. SHE HAD NOT HEARD MY INSTRUCTIONS FROM THE PURSER TO STAY SEATED. HE SAID THAT OVERALL; EVERYTHING WAS HANDLED ADEQUATELY; BUT WAS CONCERNED THAT THE LEVEL OF COM IN THE BACK CABIN WAS DEFICIENT.

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.