What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
The aircraft was cruising at FL380 with a speed of m 0.84 approximately 160 NM nne of new orleans on a south-westerly track. The f/o and s/o were at the controls, while the captain was resting in the overhead crew rest (ocr). The crew had been informed by dispatch about an area with showers over the state of Mississippi. No turbulence reports had been received at the time. The fasten seatbelt sign was not switched on.
The crew observed weather radar returns of cumulonimbus clouds (cbs) left and right of track, but based on the weather radar image the aircraft would stay clear of these cbs when maintaining their current track. No turbulence had been experienced so FAR. When flying abeam the cbs the aircraft encountered sudden severe turbulence for approximately 10 seconds. The cruise speed of m 0.84 was already equal to turbulence penetration speed and was not adjusted. The crew noticed a 20 KTS drop in indicated airspeed and alternating positive and negative vertical accelerations (g-forces).
On the navigation display, green weather radar reflections were displayed and the crew decided to turn left 10 degrees to exit the area of green radar reflections after which the turbulence ceased. Eicas messages smoke rest upr dr 4 and cargo heat bulk were displayed during the turbulence encounter, but disappeared after the event. Because of the sudden onset and short duration of the turbulence, the command ?cabin crew take your seats? Had not been given. A report to ATC was made that severe turbulence had been encountered
As the FAA filed it
THE AIRCRAFT WAS CRUISING AT FL380 WITH A SPEED OF M 0.84 APPROXIMATELY 160 NM NNE OF NEW ORLEANS ON A SOUTH-WESTERLY TRACK. THE F/O AND S/O WERE AT THE CONTROLS, WHILE THE CAPTAIN WAS RESTING IN THE OVERHEAD CREW REST (OCR). THE CREW HAD BEEN INFORMED BY DISPATCH ABOUT AN AREA WITH SHOWERS OVER THE STATE OF MISSISSIPPI. NO TURBULENCE REPORTS HAD BEEN RECEIVED AT THE TIME. THE FASTEN SEATBELT SIGN WAS NOT SWITCHED ON.
THE CREW OBSERVED WEATHER RADAR RETURNS OF CUMULONIMBUS CLOUDS (CBS) LEFT AND RIGHT OF TRACK, BUT BASED ON THE WEATHER RADAR IMAGE THE AIRCRAFT WOULD STAY CLEAR OF THESE CBS WHEN MAINTAINING THEIR CURRENT TRACK. NO TURBULENCE HAD BEEN EXPERIENCED SO FAR. WHEN FLYING ABEAM THE CBS THE AIRCRAFT ENCOUNTERED SUDDEN SEVERE TURBULENCE FOR APPROXIMATELY 10 SECONDS. THE CRUISE SPEED OF M 0.84 WAS ALREADY EQUAL TO TURBULENCE PENETRATION SPEED AND WAS NOT ADJUSTED. THE CREW NOTICED A 20 KTS DROP IN INDICATED AIRSPEED AND ALTERNATING POSITIVE AND NEGATIVE VERTICAL ACCELERATIONS (G-FORCES).
ON THE NAVIGATION DISPLAY, GREEN WEATHER RADAR REFLECTIONS WERE DISPLAYED AND THE CREW DECIDED TO TURN LEFT 10 DEGREES TO EXIT THE AREA OF GREEN RADAR REFLECTIONS AFTER WHICH THE TURBULENCE CEASED. EICAS MESSAGES SMOKE REST UPR DR 4 AND CARGO HEAT BULK WERE DISPLAYED DURING THE TURBULENCE ENCOUNTER, BUT DISAPPEARED AFTER THE EVENT. BECAUSE OF THE SUDDEN ONSET AND SHORT DURATION OF THE TURBULENCE, THE COMMAND ?CABIN CREW TAKE YOUR SEATS? HAD NOT BEEN GIVEN. A REPORT TO ATC WAS MADE THAT SEVERE TURBULENCE HAD BEEN ENCOUNTERED