Air carrier flight crew reported temporary loss of aircraft control due to encountering Clear Air Turbulence during climbout.
Synopsis
Air carrier flight crew reported temporary loss of aircraft control due to encountering Clear Air Turbulence during climbout.
Narrative
In VFR conditions and briefed FA (Flight Attendant) on turbulence procedures prior to departure since we just landed in ROC. Once we departed climbing past 18;000 it was smooth with light turbulence at this point. Clear sky's ahead I called the FA to update her on the turbulence procedures saying 'Appears the weather system moved ahead and can do service if she felt comfortable.' As soon as we got off the phone with each other it hit like a brick wall. Immediate roll to the right and airspeed fluctuations. We were in a climb upon entering turbulence but the VSI went down to 1000 feet per minute + descent. Forcing aircraft to descend while SPS Advanced message appeared on EICAS. I told FO (First Officer) to slow the aircraft down to 250 kts. I didn't say anything to ATC at first but once we started to lose altitude that's when I said we are in sever turbulence. They gave us a higher altitude and we got the aircraft back in a positive climb. I checked back with FA to make sure she and everyone was okay. Told me everyone was fine and no injuries. Sent message to Dispatch about severe turbulence encounter and would be making Maintenance write up.Cause: 180 kt. jet steam. Clear air turbulence with zero visual cues.Suggestion: Better reporting for clear air turbulence.
Second reporter narrative
While operating in VFR conditions at FL190 in a climb; the aircraft encountered an unexpected area of severe clear air turbulence. The turbulence resulted in significant airspeed fluctuations and an altitude deviation of approximately +1;000 feet. During the encounter; the aircraft experienced a rapid uncommanded roll to the right; and the SPS (Stall Protection System) Advance annunciation appeared on EICAS. The Captain had me immediately slow to 250 kts. As a result of the turbulence; I struck my head on the map light; which caused minor bruising and a headache. No loss of consciousness occurred. The turbulence event lasted approximately two minutes; after which the aircraft stabilized and turbulence continued but was light to moderate. No prior indications of turbulence were observed; and no convective activity was visible in the area at the time of the encounter.Cause: The event was caused by an unforecasted encounter with severe clear air turbulence at cruise altitude. Atmospheric conditions in the area were conducive to CAT; however; there were no visual cues; convective activity; or prior indications from available weather information or PIREPs to suggest turbulence of this severity.Suggestion: Consider increased emphasis on the use of seatbelts and shoulder harnesses at cruise altitudes; particularly when operating near known jet stream boundaries or in areas conducive to clear air turbulence. Encourage prompt reporting of clear air turbulence encounters via PIREPs to improve situational awareness for following crews
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.