Air carrier flight crew reported temporary loss of aircraft control during a severe turbulence encounter. Reportedly; the aircraft sustained minor damage in the cabin area and some passengers were thrown from their seats.
Synopsis
Air carrier flight crew reported temporary loss of aircraft control during a severe turbulence encounter. Reportedly; the aircraft sustained minor damage in the cabin area and some passengers were thrown from their seats.
Narrative
At (time) 50 NM east of the waypoint KD45A from BNA to ZZZ. We encountered severe mountain wave at Flight Level 300. We originally were at Flight Level 340; however; after coordinating with ATC were given ride reports that 320 or lower have reported better rides. At this point we were experiencing continuous light to occasional moderate chop. We turned on the seatbelt sign and had the speed window open to Mach .76. As we leveled; we experienced a brief period of smooth air. However; as the approached KD45A; we experienced a wave that began a climb rate at one point exceeding 1;000 FPM. Soon after the aircraft would reverse the climb trend and rapidly descend to 29;800 ft. The Captain and I were lifted from our seats along with loose items in the flight deck tossed. The autopilot never disconnected; however; speed was varying plus or minus 20 knots. At one point I had to extend full speedbrakes to prevent overspeed. The turbulence last 20 second and then we soon were out of the wave. Our A F/A then called us to explain what they had seen and heard. From there discussion lasting at least an hour were held between the Flight Crew; the Flight Attendants; Dispatch; and medical services. Several Passengers were thrown from their seats with some hitting the ceiling. None wanted immediate medical attention; however; two did ask for ice. Out of an abundance of caution we had medical personnel meet one Passenger who was suffering with a headache. No further severe turbulence was felt however it took time to collect all loose items that were thrown.Suggestions: In this case we had asked for ride reports along with a supposed better altitude. The event was freak and unexpected.
Second reporter narrative
We experienced an isolated incident of severe CAT (Category) during Flight XXX BNA-ZZZ. Approaching the Rockies; DEN Center reported moderate mountain wave and turbulence ahead at our altitude FL340. We warned the Flight Attendants to take their seats and to expect turbulence for the next hour. The F/As made a PA to the Passengers; and we verified the seatbelt sign was on. ATC reported better rides below FL320; so we requested FL300 which we found mostly smooth with occasional light mountain wave and turbulence. The PF slowed to turbulence penetration speed. Approximately 50 miles east of KD45A; our airspeed slowed then increased rapidly; and we experienced a sudden abrupt drop in altitude of at least -200 ft. VMO/MMO was not exceeded; and the autopilot remained engaged. The aircraft returned to FL300 and 280 knots. We reported the incident to ATC and Dispatch. The F/As reported no injuries to themselves and none of the Passengers requested help. We told the F/As to remain seated and made a PA to the Passengers. We experienced only light mountain wave and turbulence following this severe isolated incident. Later; several Passengers reported losing their seats or bumping themselves on the ceiling or other Passengers. None requested immediate medical attention. The F/As reported some minor interior damage to the aircraft. The Dispatcher contacted us; and we spoke with medical services. They gave us the ok to continue. Medical personnel met the flight to check; then released one of the Passengers.Suggestions: Coordinate a different route to avoid the area of mountain wave and turbulence completely understanding this is not always possible.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.