What happened
On June 13, 2019, at approximately 12:02 LMT, a Guimbal Cabri G2 helicopter was performing an approach to the landing pad at Dęblin (EPDE) airport. During this maneuver, the pilot noticed that the right control stick had restricted movement, specifically being unable to move from the neutral position toward the left. Simultaneously, the left control stick moved spontaneously toward the front and left positions. This movement caused the helicopter to tilt slightly to the left, but the pilot was able to complete a safe landing with no injuries and no damage to the aircraft.
The investigation
The investigation, conducted by the operator's ACSL commission, focused on the flight control system. During a subsequent inspection of the control mechanisms, a maintenance mechanic discovered that the nut securing the left control stick had become loose or unscrewed. Following the discovery, the Continuing Airworthiness Management Organization (CAMO) issued specific maintenance instructions. After these instructions were implemented, a test flight was conducted, which confirmed that the control system was functioning normally.
Findings
- The primary cause of the incident was the loosening of the nut securing the left control stick.
- The mechanical failure resulted in restricted movement of the right stick and uncommanded movement of the left stick.
Safety action
Following the incident, the operator performed inspections of the control system attachments on all Guimbal Cabri G2 helicopters in their fleet. To prevent recurrence, the nuts were marked with a color-coding agent to allow for easy visual inspection of any movement. Additionally, the operator conducted training for all flight and maintenance personnel regarding the importance of verifying the security of control system fasteners during routine operations.