Widebody Transport
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Workload
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action; General Maintenance Action
Weather
During cruise at FL360; approximate location was DEN 304 radial/120 NM; we experienced Severe to Extreme turbulence.  Airspeed initially increased by 25 kts with simultaneous severe turbulence and an approximate 300 FT increase in altitude and a rapid roll to about 20 degrees of bank.  The autopilot disconnected on its own and the airspeed then decayed rapidly by approximately 40 kts to about 20 kts below desired indicated airspeed at which point it may have momentarily entered the lower foot.  I immediately pushed the throttles forward to regain airspeed and hand flew the aircraft while the Captain called ATC for an immediate descent.  We descended to FL340 and regained our desired airspeed in the descent. We exited the severe turbulence about FL350 and once we leveled at FL340 I re-engaged the autopilot. There were no personal injuries. The Captain notified maintenance via ACARS and made an [logbook] entry.
A wide body freight aircraft flight crew reported severe clear air turbulence with a 40 KT airspeed fluctuation; a rapid climb and roll. The crew descended from FL380 and into smooth air at FL340.