O que mostra o relatório preliminar do acidente etíope B737 MAX? [fechadas]

No breve resumo, o relatório preliminar (PDF da página 33 disponível aqui) fornece esses detalhes:

Shortly after takeoff, the Angle of Attack sensor recorded value became erroneous and the left stick shaker activated and remained active until near the end of the flight. In addition, the airspeed and altitude values from the left air data system began deviating from the corresponding right side values.

Entre as poucas descobertas iniciais, o relatório preliminar tem as seguintes:

• Shortly after liftoff, the value of the left angle of attack sensor deviated from the right one and reached 74.5 degrees while the right angle of attack sensor value was 15.3 degrees; then after, the [left] stick shaker activated and remained active until near the end of the flight.

• After the autopilot disengaged, the [Flight Data Recorder] recorded an automatic aircraft nose down (AND) trim command four times without pilot’s input. As a result, three motions of the stabilizer trim were recorded. The FDR data also indicated that the crew utilized the electric manual trim to counter the automatic AND input.

Na seção que fornece detalhes derivados do Gravador de dados de voo e Gravador de voz do cockpit, os seguintes itens estão incluídos:

• At 05:40:00 shortly after the autopilot disengaged, the FDR recorded an automatic aircraft nose down (AND) activated for 9.0 seconds and pitch trim moved from 4.60 to 2.1 units. The climb was arrested and the aircraft descended slightly.
• At 05:40:03 Ground Proximity Warning System (GPWS) “DON’T SINK” alerts occurred.
• The column moved aft and a positive climb was re-established during the automatic AND motion.
• At 05:40:12, approximately three seconds after AND stabilizer motion ends, electric trim (from pilot activated switches on the yoke) in the Aircraft nose up (ANU) direction is recorded on the DFDR and the stabilizer moved in the ANU direction to 2.4 units.

Uma segunda sequência semelhante (aparar nariz automático para baixo, “NÃO SINK” do GPWS e aparar nariz elétrico comandado por piloto) ocorreu de 05: 40: 20 a 05: 40: 28.

O diagrama abaixo, de um apêndice do relatório, mostra os dados relacionados ao arremesso da aeronave do FDR desde o primeiro nariz automático até o final da gravação. (O tempo avança da esquerda para a direita.)

• At 05:40:35, the First-Officer called out “stab trim cut-out” two times. Captain agreed and FirstOfficer confirmed stab trim cut-out.

• At 05:40:41, approximately five seconds after the end of the ANU stabilizer motion, a third instance of AND automatic trim command occurred without any corresponding motion of the stabilizer, which is consistent with the stabilizer trim cutout switches were in the "cutout" position.

• From 05:40:42 to 05:43:11 (about two and a half minutes), the stabilizer position gradually moved in the AND direction from 2.3 units to 2.1 units. During this time, aft force was applied to the control columns which remained aft of neutral position. The left indicated airspeed increased from approximately 305 kt to approximately 340 kt (VMO). The right indicated airspeed was approximately 20-25 kt higher than the left.

• At 05:41:46, the Captain asked the First-Officer if the trim is functional. The First-Officer has replied that the trim was not working and asked if he could try it manually. The Captain told him to try.
• At 05:41:54, the First-Officer replied that it is not working.
• At 05:43:11, about 32 seconds before the end of the recording, at approximately 13,400 ft, two momentary manual electric trim inputs are recorded in the ANU direction. The stabilizer moved in the ANU direction from 2.1 units to 2.3 units.
• At 05:43:20, approximately five seconds after the last manual electric trim input, an AND automatic trim command occurred and the stabilizer moved in the AND direction from 2.3 to 1.0 unit in approximately 5 seconds. The aircraft began pitching nose down. Additional simultaneous aft column force was applied, but the nose down pitch continues, eventually reaching 40° nose down. The stabilizer position varied between 1.1 and 0.8 units for the remainder of the recording.
• The left Indicated Airspeed increased, eventually reaching approximately 458 kts and the right Indicated Airspeed reached 500 kts at the end of the recording.

Os eventos "nariz de aeronave automático para baixo" mencionados acima podem ser atribuídos ao MCAS (Sistema de Aumento de Características de Manobras), sobre o qual a Boeing só começou a informar os pilotos no final de novembro, o 2018.