B737 flight crew reported severe turbulence and loss of control in cruise flight.
Synopsis
B737 flight crew reported severe turbulence and loss of control in cruise flight.
Narrative
While briefing the new arrival and discussing divert options due to persisting thunderstorms around the ZZZZ airport; the aircraft experienced a rapid onset of severe turbulence without warning. The aircraft; with autopilot and autothrottle engaged; rapidly rolled left then right and started a 2000 fpm climb. The turbulence intensified to severe levels; and I made the required 'Flight Attendants be seated immediately' announcement over the PA system; while simultaneously disengaged the autopilot and smoothly arrested the rate of climb as we passed through 38;300 feet. The aircraft then rapidly transitioned to ~1000-1500 feet per minute rate of descent with equally rapid uncommanded left and right rolls. While actively manipulating the aircraft's control column to keep the wings level and avoiding G-loading the aircraft; we descended to ~37;700 feet before climbing and stabilizing our flight path at 38;000 feet. Throughout the event the aircraft did not exceed normal operating airspeed or g-load limits. A severe turbulence maintenance logbook entry was made.Contributing Factors:Rapid onset of severe turbulence without warningUnknown proximity to thunderstorms. The radar was properly tuned; but did not paint any returns nor did ATC provide any advisories.The aircraft was in a region with no internet service so our electronic flight bag's weather resources had no connectivity.
Second reporter narrative
Numerous thunderstorms in the area around ZZZZ. ATC provided reroute and radar vectors to join new arrival from the south. Seatbelt sign was on and Flight Attendants had been given command to prepare cabin for landing early in anticipation of potential turbulence in descent. Aircraft encountered unexpected turbulence in clear air while being vectored and issued holding instructions. Flight Attendants in aft galley fell down while completing final items. No turbulence reports received from preceding aircraft and radar picture was clear.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.