Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Distraction; Other / Unknown; Physiological - Other; Workload
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control
Weather
During the approach we were cleared direct down to 8000 feet from 12000 feet. During the descent Autopilot was engaged and following LNAV and VS we were encountering continuous light to moderate turbulence throughout the descent. As we passed through approximately 12000 feet and beginning to slow; we experienced severe turbulence mixed with continuous moderate [turbulence]. When we initially encountered the severe turbulence; the Autopilot disengaged; the aircraft was changing altitude and air speeds abruptly with several hundred feet of altitude change and at least plus or minus 20 to 30 knots airspeed changes. The Captain was thrown hard enough to hit the overhead panel with his head and we received a report one of our Flight Attendants had been hurt and several passengers had hit their heads. I as the Pilot Flying took manual control of the aircraft and flew the remainder of the descent and approach. The aircraft was extremely hard to control throughout most of the descent and approach as we continued to encounter continuous turbulence; strong crosswinds and wind shear. During the ensuing descent and approach the aircraft was extremely hard to control as we continued to experience moderate to severe turbulence; strong crosswind and wind shear throughout the approach. Once established inbound and cleared for the approach we were pushed several degrees off course and had some airspeed fluctuations of plus or minus 20 knots. We quickly discussed missed approach but prior to reaching 1000 feet we had regained the course; were on glide path and stabilized (properly configured) to continue the approach. We continued the approach while receiving some lower wind shear of plus or minus 10 knots down to approximately the 500 foot call. At 500 feet we were still stabilized and continued the approach to landing without further issue. Throughout the approach and landing; we had airspeed; altitude variations and heading deviations that were extremely hard to control due to the turbulence and wind shear events we were experiencing. I do not believe at any point we had any exceedances or violations; however; it was a very task saturated environment. There were no reports of the severity of the turbulence ahead of us and it was a very unexpected event.This was an example of good Crew Resource Management as the Captain and I maintained good communication throughout the event and helped to cross monitor the aircraft systems and instruments. As the pilot flying; I was entirely focused with aircraft control and the Captain doing the pilot monitoring was ensuring all the descent and approach tasks were completed. We kept good crew communication with what was happening with aircraft control and situational awareness. A recommendation is for pilots to ensure they continue to practice hand flying skills for situations like this. The autopilot was unusable; and I was thankful I constantly practice hand flying the airplane. It helped me with confidence to control the airplane to the best of my ability in a situation where the aircraft is being tossed around by turbulence.
Pilot reported encountering a loss of control due to severe turbulence and wind shear on descent and approach into SEA.