Date: 202102
Local time of day: 1801-2400
Location: ZKC.ARTCC, KS
Flight conditions: IMC
Weather elements / visibility: Turbulence
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZKC
ATC / advisory: Center ZKC
Reporter organization: Air Carrier
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Detector: Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Clearance; Flight Crew Regained Aircraft Control; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Contributing factors: Weather; Airspace Structure; Procedure
Primary problem: Weather

Narrative: The flight was cruising at 35;000 ft. (FL350) in Instrument Meteorological Conditions (IMC). The flight attendants had been briefed earlier about turbulence along the route of flight. When the turbulence became constant moderate; the flight attendants were informed via the public address (PA) system to 'take their seats.' The flight was deviating around weather and needed a left deviation and attempted request a deviation from ATC; however; due to frequency congestion this was causing a delay in deviation. The Captain executed the deviation out of safety (emergency authority) and had the First Officer announce the deviation to ATC; not long after the deviation severe turbulence was encountered lasting approximately one minute. The aircraft was out of control with large airspeed; attitude; and altitude deviations. The severe turbulence caused a 500 foot altitude deviation (35;500 ft.) which triggered a TCAS alert. All automation disconnected in the turbulence and the Captain assumed manual flight control. The second aircraft was acquired visually; and the Captain manually maneuvered to regain control; avoid the aircraft; and return to 35;000 ft. Once clear of the turbulence; the auto-throttles and autopilot were re-engaged; and ATC informed about the location and magnitude of the severe turbulence. The First Officer was tasked to check on the status of the flight attendants and passengers. There were no flight attendant or passenger injuries. Both during flight and upon landing; Maintenance Control; Dispatch; and Operations was kept informed of the severe turbulence encounter along with crew and passenger status. A combination of active weather with turbulence across much of the central United States; high workload environment; saturated ATC frequencies.One cannot control the weather; gather as much information as possible about the route and possible threats along the way.




Synopsis: Air carrier pilot reported severe turbulence encounter during cruise and ATC communication problem that resulted in altitude excursion; track deviation and conflict with other aircraft.