Air carrier flight crew reported temporary loss of aircraft control during cruise due to encountering severe turbulence in ZMA airspace.
Synopsis
Air carrier flight crew reported temporary loss of aircraft control during cruise due to encountering severe turbulence in ZMA airspace.
Narrative
We got vectored several times to deviate from thunderstorms. Initially our flight release had us going over the East coast on our way to Miami. ATC instructed us to fly towards the West coast because according to them there was a better chance to stay away from the bad weather. During the entire flight our weather radars were sweeping the weather ahead of us and we noticed nothing was depicting while at flight level 330 while in IMC and no precipitation. While at flight level 330 we experienced a sudden severe turbulence followed by a loss of altitude and constant changes in airspeed. I put my left hand on the thrust levers to assure we had the necessary power to keep constant airspeed and to maintain altitude. During the encounter we lost about 400 feet of altitude and it lasted a few seconds after the initial upset.Cause: Flying around adverse weather and being vectored by ATC to avoid thunderstorms.Suggestions: Always keep the weather radar while convective weather around a big area. Captain and me had our weather radars active in order to be able to plan and take on time decisions on better and safe routing for our flight.
Second reporter narrative
CA was PF and FO was PM. On preflight; the FO and I agreed that the filed routing looked best to proceed down the Florida east coast and join the ZZZZZ arrival into MIA. Flight attendant were told to remain seated for the duration of the flight; due to thunderstorms over central and northern Florida.On departure from ZZZ; we were vectored southeast and given right deviation to avoid weather/thunderstorms. Our plan [was to] deviate southeast of weather cells and then proceed direct to ZZZZZ; continuing to follow the filed flight plan route. ATC advised us that MIA center needed us to turn South to GAWKS and join the FROGZ arrival. We queried ATC and voiced our concerns about the west coast weather. ATC acknowledged our concerns and said this routing was needed for MIA Center. We were given right deviations to avoid weather north of GAWKS; which showed heavy convective activity from visible lightning and red/yellow indications from the radar. The next controller gave right deviations and clearance to proceed direct to KLEET when able. At this point; we were level at FL330; cruising at M0.76; and clear of the convective weather. We saw a small (approximately 5 miles in diameter); isolated; green cell that was southeast of our position on the radar depiction. Nothing worse than light and occasional moderate turbulence was experienced. ATC advised us that arriving aircraft had only reported light to moderate turbulence. We continued to stay on right deviations to clear the small isolated green cell just out of caution. I tilted my radar down to confirm the cell was painting correctly on the radar (approximately -0.5 to get the clearest reading without ground clutter at approximately 25 nm) and advised the FO that we should be able to turn direct the KLEET after the flight path showed south of the cell. At this point; the FO had his radar tilted up at approximately +2.0. I told the FO to reduce the tilt in order to view the light precipitation cell. We proceeded direct to KLEET after the dashed direct to line showed us well clear of the small cell. There was no depiction of any precip on our flight path direct to KLEET. The small isolated green cell was at least 10 nm north of our position. Current conditions were IMC but no visible precipitation and no more visible lightning; occasional light to moderate chop. After a few minutes of turning direct to KLEET we experienced severe turbulence. The airspeed became erratic by rapidly decreasing and trending a large decrease. The plane violently began to climb (approximately 100-200 ft) then rapidly descend. The FO took manual control of the throttles trying best to maintain M0.76. The aircraft was unable to maintain altitude and became stable at 32;600 FT. The FO began the climb back to FL330 and I advised ATC that we experienced severe turbulence. I immediately called the flight attendants to insure there were no injuries. I advised ATC that there were no injuries; no aircraft damage and no precip at the time of the severe turbulence. We continued the flight to MIA since there were no injuries or noticeable damage to the aircraft.Cause: Severe weather over Florida and an unexpected arrival change into MIA.It may have been a more conservative option to stay on the full arrival and not accept a clearance direct to KLEET. However; other aircraft were ahead of us on the arrival and there was no indication of threats/turbulence/precip going direct to KLEET.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.