What happened
On September 14, 2015, an Embraert 170 was performing an approach to landing at LFPG when the autopilot unexpectedly disconnected at an altitude of approximately 1,400 feet. Following the disconnection, the crew experienced difficulties manually controlling the aircraft's pitch. Despite these challenges, the approach was continued and the aircraft landed safely. Following the flight, the crew recorded the event in the technical log and filed an Air Safety Report (ASR).
The investigation
The investigation examined flight data recorder parameters and recent maintenance history. Analysis of the flight data revealed that opposing forces were acting on the control columns during the approach. Such symptoms are characteristic of a physical obstruction preventing the free movement of the controls. The investigation also noted that the aircraft had undergone altitude-related repairs on September 7, 2015, and had experienced a separate autopilot disconnection during a flight on September 10, 2015. During a pre-flight walk-around, the crew had also noted unusual clicking sounds on the right side of the elevator movement.
Crucially, investigators discovered that on the day prior to the incident, the pilot's seat cushion had been replaced due to an insecure attachment.
Findings
- The primary cause of the autopilot disconnection was increased forces on the control columns caused by the improperly secured pilot seat cushion, which obstructed the movement of the controls.
- The crew reported that while the elevator trim functioned correctly, the physical force required on both control columns was approximately three times higher than normal.
- Maintenance records were reviewed to ensure all recent servicing, including the seat cushion replacement and previous altitude-related repairs, were performed according to documentation.