What happened
During the initial climb phase of flight, the upper cowling on the right engine separated from the aircraft structure. The detached component traveled rearward along the fuselage and impacted the window located at the right rearmost passenger seat. Fortunately, this specific seat was unoccupied at the time of the incident. Following the separation, the pilot took immediate action to secure the affected engine. After ensuring the aircraft was under control, the pilot executed an uneventful landing without further complications.
The investigation
A mechanical examination was conducted to determine the root cause of the structural failure. Inspectors focused on the attachment points and guide mechanisms for the cowling panels. The analysis revealed significant wear within the lower cowling guide pin holes. This excessive wear compromised the integrity of the fastening system, allowing the upper cowling to detach under aerodynamic loads during climb.
Findings
The primary factor contributing to this event was mechanical degradation. Specifically, excessive wear in the lower cowling guide pin holes prevented the cowling from remaining secured. The pilot's decision to secure the engine and land safely mitigated any potential safety risks associated with the detached component.