Accident: Astana E190 at Alverca on Nov 11th 2018, severe control problems
On May 31st 2019 the GPIAA changed the classification of the occurrence from serious incident to accident. The GPIAA released their preliminary report and provided preliminary findings:
The left and right aileron surfaces control the rolling (lateral) movements of the aircraft with the actuation of the two control yokes or with the autopilot controls. The ailerons are assisted by the flight mode spoilers (roll spoilers).
The aileron control system is actuated by rotation of either the pilot or co-pilot aileron control yokes which are mechanically connected to each other and that through the cable circuit, the torque tubes and the quadrants, transmit these movement to the Power Control Unit - PCU which moves the aileron surface.
The PCUs are mechanically controlled through the cable system and are hydraulically powered.
The data collection during the initial investigation phase included a detailed examination of the aircraft flight controls and an incorrect ailerons control cable system installation was confirmed on both semiwings.
By introducing the modification iaw Service Bulletin 190-57-0038 during the maintenance activities, there was no longer the cable routing and separation around rib21, making it harder to understand the maintenance instructions, with recognized opportunities for improvement in the maintenance actions interpretation.
The message “FLT CTRL NO DISPATCH” was generated during the maintenance activities, which in turn originated additional troubleshooting activities by the maintenance service provider, supported by the aircraft manufacturer. These activities, which lasted for 11 days, did not identify the ailerons' cables reversal, nor was this correlated to the "FLT CTRL NO DISPATCH" message.
From the investigation process carried out so far, it also resulted in the identification of deviations to the internal procedures by the maintenance service provider, which led to the error not being detected in the various safety barriers designed by the regulators, aeronautical maintenance industry and within the maintenance service provider implemented system.
The ailerons incorrect operation caused by the control cables reversal, was not identified in the aircraft operational checks (flight controls check) by the operator crew.
The GPIAA reported the damage:
From the preliminary analysis to the condition of the aircraft after the event flight, significant structural damage in both semi-wing, fuselage and flight control surfaces was verified, which led the GPIAAF to change the initial classification of serious incident to accident, following ICAO Annex 13 recommendations.
The aircraft was returned to the operator on Jan 21st 2019, who is currently evaluating the aircraft and deciding about further action. The investigation has completed the collection of facts and is now engaging in analysis and drafting the final report.