What happened
On January 17, 2020, an Airbus Helicopters EC135 T3, registration PR-EBS, was conducting a police operation from Fortaleza to Sobral, Brazil. The aircraft was carrying two pilots and five police officers. During the climb to FL 065, while traversing a cloud layer, the commander engaged the autopilot coupled with the Global Navigation System (GNS). This caused the aircraft to execute a 60-degree left turn to intercept the newly programmed route.
Upon noticing the turn while in IMC, the commander manually intervened by overriding the autopilot. This intervention increased the left bank angle and induced a nose-down attitude. The maneuver caused the aircraft to exceed its Never Exceed Speed (VNE) and subsequently led to the rotor RPM exceeding safe limits after the pilot lowered the collective to recover. The crew managed to stabilize the aircraft at approximately 1,000 feet and continued the flight to the destination without further incident. There were no injuries and no damage to the aircraft.
The investigation
CENIPA investigators analyzed data from the aircraft's Flight Data Continuous Recording (FDCR) and the "Vision 1000" cockpit camera. The investigation established that the aircraft was operating within weight and balance limits and that all required certifications were valid.
Investigators found that the commander had taken over the task of updating the flight route in the GNS after a delay by the co-pilot. This action diverted the commander's attention from flight monitoring. The investigation also noted that the aircraft's Standard Operating Procedures (SOP) were undergoing updates at the time and lacked specific instructions regarding the division of tasks between pilots during flight operations.
Findings
- Spatial disorientation: The commander's ability to perceive and interpret flight stimuli was compromised, likely due to a lack of external visual references while flying through clouds.
- Ineffective Crew Resource Management (CRM): The commander's decision to manage the navigation system personally diverted attention from primary flight duties.
- Inadequate task delegation: The lack of defined procedures for task sharing between the pilot flying and the pilot monitoring contributed to the loss of situational awareness.
- Manual control errors: The pilot's manual override of the autopilot intensified the bank angle and induced the nose-down attitude that led to the overspeed.