Air carrier flight crew reported severe turbulence at cruise altitude resulted in an altitude deviation and a Flight Attendant injury. The Captain recovered the aircraft and continued to destination where medical personnel met the flight.
Synopsis
Air carrier flight crew reported severe turbulence at cruise altitude resulted in an altitude deviation and a Flight Attendant injury. The Captain recovered the aircraft and continued to destination where medical personnel met the flight.
Narrative
Aircraft X ZZZ - ZZZ1 encountered intermittent light to moderate turbulence not associated with a weather system during the first half of the flight. Turbulence was being monitored by WSI; the app; in addition to talking with ATC. The Captain had the flight attendants sitting down until we were clear of the moderate turbulence. The passenger seat belt sign was on. Approximately 10 minutes after the flight smoothed out and both apps showed no further turbulence along with no reports from ATC for the remainder of our flight; the Captain called the Flight Attendants to allow them to resume their duties. The passenger seat belt sign was still illuminated. Five minutes later; 25 miles east of ZZZ2; after being in completely smooth air at 25;000 ft. and a slower airspeed of 270 - 280 KIAS the plane hit a pocket; 2 - 3 seconds of severe turbulence with a jolt that immediately kicked the autopilot off and sent our iPads to the ceiling and both the Captain and I were butt off the seat and seat belts holding us in place. The Captain recovered the aircraft; which had minimal loss of altitude during the event; and turned the autopilot back on. We were back in smooth air after those few seconds. The Captain attempted to call the Flight Attendants for several minutes until they answered. The #4 Flight Attendant was on an aft galley jump seat when the turbulence lifted them off the seat airborne then brought them back down onto the jump seat which hit their midsection. There was a doctor on board that was able to assist with [Flight Attendant] #4. ATC was notified of the severe turbulence with a Flight Attendant injury and Dispatch was called. The flight landed at ZZZ1 about 30 minutes later with medical personnel standing by which took [Flight Attendant] #4 to the hospital. Due to the flight attendants performing their duties after a severe turbulence event the information was slow to make it to the cockpit. The Captain and I determined the quickest course of action was to continue to ZZZ1 executing the straight in approach that was already set up.Cause: Severe Turbulence that was not forecast and not reported by ATC. Suggestions: As technology advances and newer weather satellites are launched; provide better real time forecasting available to pilots.
Second reporter narrative
During preflight briefing; I informed Flight Attendant Number 1; and Flight Attendant Number 4; who was present for part of it. I don't recall when they arrived to take part and Flight Attendant Number 2; had not arrived yet. I showed Flight Attendant Number 1 the WSI [app] turbulence plot and expected it to start about 45 minutes into the flight. I told them I'm very cautious when it comes to turbulence with them and like to have them seated when I'm aware of it being a factor. I tell every crew that I don't want them to remember my face because someone was injured in a turbulence event.Turbulence started a little sooner than I thought and we began moderate turbulence procedures; prior to encountering the moderate; which had pockets and lasted about 30 minutes. FO (First Officer) was using the application and I had the WSI turbulence plots on our iPads at the same time; so we could evaluate what altitudes at what locale were better. Aircraft were asking Center for better rides all over southern State 1 and west State 2; due to a strong jet stream. There was no convective activity associated with the moderate turbulence. The skies were clear and no weather phenomena was observed to alert us to any possible turbulence. FO and I made a plan around the halfway point to descend from FL290 to FL250; due to the turbulence plots on both apps and took the slower speeds; in case we encountered the moderate turbulence other aircraft were experiencing. I believe the cruise speed at FL250 was 270 - 280 KIAS. There was no convective activity associated with the turbulence.We were east of ZZZ2 and having been in smooth air for 5 to 10 minutes and consulting the WSI and applications; which indicated all clear of turbulence at all levels; I called the Number 1 FA (Flight Attendant); and told them I was leaving the seat belt sign on for a while longer; but if they needed to resume their duties just be careful; but all indications were a smooth flight ahead. A few minutes later we experienced severe clear air turbulence; about 2 seconds in duration; which was enough to turn off the autopilot; throw our iPads out of their cradles and lift us up in our seats against the lap belts. I gained control; climbed the 100 ft. back to FL250 and selected the autopilot back on. It took a few minutes to regain communication with the cabin; which was very worrisome and seemed like an eternity. We were close to starting down on the star when we received the initial report of no injuries. FO reported the event to ATC and then took over flying duties and the radios; so I could call and alert Dispatch and Maintenance Control; through the crew phone. We also informed ATC about no injuries. I resumed flying duties; FO radios; when we were informed of Flight Attendant 4 injury. I don't recall how far down the arrival we were and the severity of the injury was not known. I asked Flight Attendant 1 if medical personnel were onboard and they were checking. I didn't know the severity of the injury; so we were waiting for more information before asking for an incident report and [requesting priority handling]. We were also descending on the STAR to ZZZ1; but did ask for medical to be standing by upon arrival with both ATC by radio and Dispatch via ACARS. Dispatch asked for their name and age. After landing and shutting down at gate in ZZZ1; I went to the back to check on Flight Attendant 4 and see if I could assist before the EMTs made it onboard. This is when I found out a paramedic [a passenger]; was attending to Flight Attendant 4. EMTs came onboard; while passengers remained seated and took them out via aisle chair and wheel chair to the terminal. We went to the hotel and I tried for an hour to get the name of the hospital they were taken to; so I could sit with them and bring their bags; if they needed to stay overnight. That information was not given; due to privacy concerns. The Duty Pilot informed me someone from the station was going to stay with and assistthem. They also asked if I would take their bags to their room; which I did and left the key at the front desk.Cause: Severe clear air turbulence. Suggestions: I know of none; other than not having cabin service. We followed our SOPs; training and continuous evaluation of the turbulence plots to find the safest and most comfortable ride for all of us. This was a busy flight prior to the event. We were in light turbulence and using our tools; were able to implement moderate turbulence procedures; prior to encountering the moderate ride. Fortunately; none of our passengers or other crew were injured.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.