Narrative:

In-flight; while in smooth air with a good ride; cruising at flight plan FL270; ca observed and verbally communicated to the first officer a deep auto-throttle reduction to approximately 50% N1. As a precaution ca turned on the seat belt sign believing this throttle movement might be associated with unstable air. With first officer as pilot flying; aircraft encountered the first vertical jolt. On first impression and without any warning other than the throttle movement; the turbulence initially felt like wake turbulence. However; it persisted and the ride rapidly degenerated into a series of waves; some moderate and some severe with short windows of relatively calmer; manageable air for the next 40 minutes of flight. Upon the first sudden onset with this turbulence the ca commanded the flight attendants to take their seats immediately over the PA system. The cockpit crew asked for an altitude change to FL310 and repeatedly asked ATC for guidance of ride reports and a smooth altitude. ATC may not have understood or may not have had any information to give; in either event no useful information was forthcoming. The climb clearance to FL310 was accompanied by a frequency change where the next controller indicated higher altitudes were worse including moderate turbulence at FL340 from an aircraft approximately 160 miles ahead of us. The turbulence remained as we got close to FL310 and with rides ahead and higher appearing no better we asked for FL290 seeking relief from often severe jolts which sent the aircraft into the overspeed (red) a/south tape a few times in spite of having autopilot and auto throttles engaged throughout. I opted to descend to open up the 'a/south window' rather than attempt higher altitudes given the dismal ATC reports at higher altitudes. [Over the next 40 minutes] we sought relief from these continuous moderate; sometimes severe turbulent horizontal and vertical jolts between FL270 and FL340; to no avail until exiting the system near zzzzz. I had limited ability to obtain information from the cabin crew though I knew via interphone communication with my purser as well as from the aft cabin that I had at least 2 fas hurt; one with a shoulder injury and another who was reported unconscious for a few minutes after having her leg pinned by a cart. Subsequently; the latter was reported conscious and in a jumpseat with leg abrasions. Control of the aircraft and ATC communication as well as the pandemonium in the passenger cabin throughout the 40 minutes of turbulence restricted my ability to assess and comprehend the totality of conditions in the cabin. Both cockpit crew members who started the event in the bunks were assisting the cabin crew. For a large part of the turbulence encounter; movement through the cabin was restricted and during periods when they could move they were clearing broken glass; plates; food; and carts that had in some cases; contacted the ceiling. Only after departing the turbulent airspace was I able to really begin assessing with my copilots conditions in the cabin. Those conditions and crew injuries along with increasing reports of passenger injuries made me believe a divert was probable. The first officer flew the airplane and prepared SELCAL/oceanic entry as we proceeded. I satcom called dispatch to ask for assistance with any ability they might have to assess real time airframe or engine parameters for exceedances on the aircraft. While that conversation was inconclusive; my suspicion was that the airframe may have exceeded g limits and could have sustained damage. I was most reluctant to continue an oceanic crossing considering injured crew members and passengers; passenger service concerns; and finally; possible airframe damage. I indicated to the dispatcher that given the totality of circumstances; I wanted to divert; probably to ZZZZ with his concurrence. I requested him to explore all weather resources and send me a route that would minimize returning through the turbulence we had endured. Once the route was received from dispatch (absent the altitude I had requested) we notified ATC of our intent to divert to ZZZZ via that route for medical emergency and overweight landing. The preparation; request; and receipt of this ATC clearance required much more time than I hoped. Assigned FL350 for oceanic crossing; ATC assigned FL360 for the divert. We rejected that level based on aircraft performance. They then assigned FL320. We accepted this level and reaching that altitude were cleared to turn on the prescribed route to ZZZZ. The balance of the flight involved many communications with queries from dispatch; company; and ATC concerning crew/passenger needs/conditions... Some duplicate requests. We ran overweight landing checklist for a landing at 493k lbs. Landed uneventfully. Gentle touchdown in visual weather conditions. Lots of medical and media at gate on arrival. To my knowledge; 12 passengers and 3 flight attendants received medical assistance... The most serious a fractured neck vertebrae and in another case; a fractured shoulder. Aircraft exhibited visual physical damage between the engines and wing roots 2 - 3 ft. Aft of the leading edge on the underside of each wing. Skin was wrinkled at repetitive intervals every 18 - 24 inches. Logbook was completed and aircraft returned to ops/maintenance who indicated foreign authorities would want to review cockpit voice and data recorder. I responded that I had not taken any action with either and the aircraft was theirs to do as they wished. The crew left the airport with requests from the media which we declined. Suggestions: subcontracted weather services like wsi are completely inadequate compared to a meteorology department whose services could be incorporated into the flight planning/dispatch system. Reports of extreme weather over the area were recurrent in the period during and after this event. However; I did not have access to this information. I believe this event is a result of a failure in the flight planning/dispatch system.

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Original NASA ASRS Text

Title: B777 flight crew reported encountering severe turbulence on a international flight that resulted in injuries to cabin crew and passengers; as well as overstress damage to the aircraft. Reporter was critical of weather forecasting resources available to him during flight planning.

Narrative: In-flight; while in smooth air with a good ride; cruising at flight plan FL270; CA observed and verbally communicated to the FO a deep auto-throttle reduction to approximately 50% N1. As a precaution CA turned on the seat belt sign believing this throttle movement might be associated with unstable air. With FO as pilot flying; aircraft encountered the first vertical jolt. On first impression and without any warning other than the throttle movement; the turbulence initially felt like wake turbulence. However; it persisted and the ride rapidly degenerated into a series of waves; some moderate and some severe with short windows of relatively calmer; manageable air for the next 40 minutes of flight. Upon the first sudden onset with this turbulence the CA commanded the flight attendants to take their seats immediately over the PA system. The cockpit crew asked for an altitude change to FL310 and repeatedly asked ATC for guidance of ride reports and a smooth altitude. ATC may not have understood or may not have had any information to give; in either event no useful information was forthcoming. The climb clearance to FL310 was accompanied by a frequency change where the next controller indicated higher altitudes were worse including moderate turbulence at FL340 from an aircraft approximately 160 miles ahead of us. The turbulence remained as we got close to FL310 and with rides ahead and higher appearing no better we asked for FL290 seeking relief from often severe jolts which sent the aircraft into the overspeed (red) A/S tape a few times in spite of having autopilot and auto throttles engaged throughout. I opted to descend to open up the 'A/S window' rather than attempt higher altitudes given the dismal ATC reports at higher altitudes. [Over the next 40 minutes] we sought relief from these continuous moderate; sometimes severe turbulent horizontal and vertical jolts between FL270 and FL340; to no avail until exiting the system near ZZZZZ. I had limited ability to obtain information from the cabin crew though I knew via interphone communication with my purser as well as from the aft cabin that I had at least 2 FAs hurt; one with a shoulder injury and another who was reported unconscious for a few minutes after having her leg pinned by a cart. Subsequently; the latter was reported conscious and in a jumpseat with leg abrasions. Control of the aircraft and ATC communication as well as the pandemonium in the passenger cabin throughout the 40 minutes of turbulence restricted my ability to assess and comprehend the totality of conditions in the cabin. Both cockpit crew members who started the event in the bunks were assisting the cabin crew. For a large part of the turbulence encounter; movement through the cabin was restricted and during periods when they could move they were clearing broken glass; plates; food; and carts that had in some cases; contacted the ceiling. Only after departing the turbulent airspace was I able to really begin assessing with my copilots conditions in the cabin. Those conditions and crew injuries along with increasing reports of passenger injuries made me believe a divert was probable. The FO flew the airplane and prepared SELCAL/oceanic entry as we proceeded. I SATCOM called Dispatch to ask for assistance with any ability they might have to assess real time airframe or engine parameters for exceedances on the aircraft. While that conversation was inconclusive; my suspicion was that the airframe may have exceeded g limits and could have sustained damage. I was most reluctant to continue an oceanic crossing considering injured crew members and passengers; passenger service concerns; and finally; possible airframe damage. I indicated to the Dispatcher that given the totality of circumstances; I wanted to divert; probably to ZZZZ with his concurrence. I requested him to explore all weather resources and send me a route that would minimize returning through the turbulence we had endured. Once the route was received from Dispatch (absent the altitude I had requested) we notified ATC of our intent to divert to ZZZZ via that route for medical emergency and overweight landing. The preparation; request; and receipt of this ATC clearance required much more time than I hoped. Assigned FL350 for oceanic crossing; ATC assigned FL360 for the divert. We rejected that level based on aircraft performance. They then assigned FL320. We accepted this level and reaching that altitude were cleared to turn on the prescribed route to ZZZZ. The balance of the flight involved many communications with queries from Dispatch; company; and ATC concerning crew/passenger needs/conditions... some duplicate requests. We ran overweight landing checklist for a landing at 493k lbs. Landed uneventfully. Gentle touchdown in visual weather conditions. Lots of medical and media at gate on arrival. To my knowledge; 12 passengers and 3 flight attendants received medical assistance... the most serious a fractured neck vertebrae and in another case; a fractured shoulder. Aircraft exhibited visual physical damage between the engines and wing roots 2 - 3 ft. aft of the leading edge on the underside of each wing. Skin was wrinkled at repetitive intervals every 18 - 24 inches. Logbook was completed and aircraft returned to ops/maintenance who indicated foreign authorities would want to review cockpit voice and data recorder. I responded that I had not taken any action with either and the aircraft was theirs to do as they wished. The crew left the airport with requests from the media which we declined. Suggestions: Subcontracted weather services like WSI are completely inadequate compared to a meteorology department whose services could be incorporated into the flight planning/dispatch system. Reports of extreme weather over the area were recurrent in the period during and after this event. However; I did not have access to this information. I believe this event is a result of a failure in the flight planning/dispatch system.

Data retrieved from NASA's ASRS site 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.