Preliminary report for the initially reported “turbulence fatality” from earlier this month just released. Turns out, nothing to do with turbulence and a lot more going on than was initially believed (shocker).
“The flight crew reported that around 6,000 ft, they observed multiple EICAS caution messages. The crew recalled EICAS messages of ‘AP STAB TRIM FAIL’ [autopilot stabilizer trim failure] ‘MACH TRIM FAIL’ and ‘AP HOLDING NOSE DOWN’. Neither crewmember could recall exactly what order the EICAS messages were presented. They also reported that additional EICAS messages may have been annunciated.
The PIC asked the SIC to refer to the quick reference handbook. The SIC, via an electronic flight bag (iPad), located the quick reference card and the ‘PRI STAB TRIM FAIL’ [Primary Stabilizer Trim Failure] checklist. The SIC visually showed the PIC the checklist, and they both agreed to execute the checklist. The first action on the checklist was to move the stabilizer trim switch (‘STAB TRIM’), located on the center console, from ‘PRI’ (Primary) to ‘OFF.’ The SIC read the checklist item aloud and he subsequently moved the switch to off.
As soon as the switch position was moved, the airplane abruptly pitched up. The PIC reported that his left hand was on the flight controls and his right hand was guarding the right side of the flight controls. He immediately with both hands regained control of the airplane in what he estimated to be a few seconds after the airplane’s pitch oscillated up and down. During the oscillations, the PIC instructed the SIC to move the stabilizer trim switch back to the primary position, which the SIC accomplished.
…
The airplane immediately pitched up to about 11° and reached a vertical acceleration of about +3.8g. The airplane subsequently entered a negative vertical acceleration to about -2.3g. The airplane pitched up again to about 20° and a vertical acceleration of +4.2g was recorded. The stall protection stick pusher activated during this pitch up; subsequently, vertical acceleration lowered to about +2.2g which was followed by a cutout of FDR data.”
All of this occurring after an initial aborted takeoff due to a pitot cover-induced airspeed disagree, followed by a takeoff with unpopulated v-speeds. Plenty more happening on the ground as well. Certainly a lot going on here…
