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The Center for Research and Prevention of Aeronautical Accidents (CENIPA) from Brazil published the final report of the investigation into the tragic flight accident 2283 from Voepass Linhas Aéreas, It happened 9 august 2024.
The document concludes that a combination of adverse weather conditions due to severe freezing, Intermittent failures in the aircraft's pneumatic de-icing system and operational decisions under organizational pressure triggered a loss of control in flight (LOC-I) and the subsequent impact on a residential area of Vinhedo, Saint Paul. The sinister, that took the lives of the 62 people on board, marked the definitive milestone that led to the stoppage of operations and the final closure of the Brazilian regional airline.
Final Voepass ATR Accident Report 72
The 9 august 2024, a ATR 72-500 from Voepass Linhas Aéreas suffered a loss of aerodynamic lift while cruising at flight level FL170 en route to San Pablo. The aircraft experienced severe ice buildup on the airfoils., which dramatically increased aerodynamic drag and reduced flight speed. After disconnection of the autopilot and activation of the cockpit alarms, The plane entered an irreversible loss of control that evolved into a flat spin (flat spin), impacting the land within a residential complex in the municipality of Vinhedo.
- Date and time: 9 august 2024, approximately at 16:22 UTC (13:22 local time).
- Location: Municipality of Vinhedo, Estado de San Pablo (SP), Brazil.
- Operator: Voepass Linhas Aéreas.
- Aircraft: ATR 72-212A (ATR 72-500).
- Serial number: MSN 908.
- Registration: PS-VPB.
- Damage to the aircraft: Destrucción total por impacto e incendio subsiguiente.
- Victims: 62 deceased (58 passengers and 4 crew).
Operation summary
La aeronave despegó del Aeropuerto Regional de Cascavel (CAC/SBCA) at 14:58 UTC con destino al Aeropuerto Internacional de San Pablo-Guarulhos (GRU/SBGR), cumpliendo el vuelo regular 2283. El despacho y la planificación previa del vuelo preveían la presencia de condiciones meteorológicas propicias para la formación de hielo en la ruta prevista sobre el estado de San Pablo. Durante el ascenso y la fase de crucero a 17,000 pies (FL170), la tripulación encendió los sistemas térmicos de protección contra hielo (Anti-Ice). Nevertheless, a medida que la aeronave ingresaba en la zona crítica de congelamiento meteorológico, el sistema neumático de deshielo de las alas y estabilizadores (Airframe De-Icing) had intermittent malfunctions, reducing the aircraft's ability to dislodge layers of ice accumulated on the leading edges.
Research findings
The final report drawn up by CENIPA highlights that the triggering factor was severe aerodynamic degradation caused by excessive ice accumulation on the wings and horizontal stabilizer., combined with the lack of effectiveness of the De-Icing system. Among the main conclusions presented in the report are the following::
- Defrost system inoperability: Flight data recordings (FDR) and cabin audio (CVR) confirmed multiple attempts by the crew to activate the Airframe De-Icing system, which was disconnected recurrently due to fluctuations in the pneumatic bleed pressure of the engines.
- Situational awareness and speed management: Despite visual and audible warnings from the aircraft performance monitoring system (APM), The crew maintained altitude at FL170 while airspeed continued to progressively decrease., exceeding the safety margins established for flight in severe ice conditions.
- Loss of control and flat spin: When approaching the critical speed, loss protection system (Stall Protection System) activated lever vibrator (Stick Shaker) and the lever pusher (Stick Pusher). Sudden autopilot disconnection, added to the aerodynamic asymmetry produced by the ice, caused an abrupt roll and subsequent entry into a flat spin without sufficient altitude margin for recovery.
- Organizational factors and supervision: The investigation pointed out management deficiencies in the airline regarding the maintenance of deferred, monitoring operational safety and training crews for early recognition and avoidance of extreme icing conditions. These findings motivated inspection actions by the National Civil Aviation Agency. (ANAC) of Brazil that led to the suspension of operations and the subsequent definitive closure of Voepass.
Summary of the crew's performance during the cruise phase
During the cruising phase 17,000 pies (FL170), the flight crew 2283 from Voepass faced a progressive degradation of weather conditions and aircraft performance. Cockpit voice recorder records (CVR) and flight data (FDR) revealed a lack of effective monitoring of basic flight parameters, as the indicated speed (IAS), as the plane entered the severe icing zone.
As ice accumulated on the structure, performance degradation warning system (Performance Loss) issued audible and visual warnings in the cabin. Nevertheless, The pilots did not adjust engine power or initiate a pre-emptive descent to warmer altitudes to emerge from the icing layer., keeping the autopilot engaged in altitude mode (ALL fashion). This condition led the automatic system to gradually increase the angle of attack (pitch up) to sustain the 17,000 pies, sacrificing airspeed to compensate for the additional weight and drag generated by ice.
Start of emergency and loss of control
The emergency was triggered when the aircraft's speed fell below the minimum maneuvering limit in icy conditions.. Loss protection system (Stall Protection System) activated joystick vibration (stick shaker) to warn pilots about the proximity of aerodynamic collapse. Immediately after, the autopilot automatically disconnected when it could not maintain the required flight parameters.
By taking manual control of the aircraft, the pilots' reaction was disorderly and contrary to standard stall recovery procedures (stall recovery). Instead of reducing the angle of attack by pushing the stick forward (pitch down) and apply maximum power, the crew carried out erratic control commands that aggravated the aerodynamic condition. The asymmetry in lift caused by the irregular accumulation of ice on the wings caused the ATR 72 perform an abrupt and uncontrollable roll, entering a deep stall that resulted in a flat spin (flat spin). During the dizzying descent, The high rotation rate and lack of effective airflow over the control surfaces prevented any attempted maneuvering before impact..
You can read the entire investigation and report, in English, In this link: https://sistema.cenipa.fab.mil.br/cenipa/paginas/relatorios/rf/en/RF_PS-VPB_09_08_2024_Eng.PUB..pdf
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