What happened
During pre-take-off checks at Fortnum aerodrome, the flight crew of VH-NYA, a Cessna 208B Caravan, experienced a propeller strike. Following established operator procedures to protect propellers from stone damage, the crew had parked the aircraft over conveyor belt matting on the apron. The aircraft was positioned such that the left propeller disc was located directly above the intersection of two conveyor belts. As the engine was operated, the airflow generated at the propeller tips created enough lifting force to displace the matting. Because the corner nails of the inner belt were not sufficiently secure, the edge of the belt was pulled into the propeller arc. This resulted in one propeller blade being sheared off near the hub and damage to a second blade. The loss of the blade caused severe engine vibration, leading to further damage to the aircraft.
The investigation
The investigation examined the condition of the apron surface and the procedures used by the operator. While the operator had used this matting for approximately three years without incident, the investigation found that the aerodrome's risk assessment and a recent consultant audit had failed to identify the matting as a potential hazard. This oversight was likely due to a lack of formal specifications, installation instructions, or maintenance requirements for this non-standard apron surface. While the aerodrome reporting officer and previous flight crews had not noticed any issues with the matting, the investigation noted that if other aircraft had used the same alignment, the security of the belts might have progressively degraded over time. On this specific occasion, the crew did not inspect the matting prior to the engine start.
Findings
- The primary cause of the incident was the conveyor belt matting being drawn into the propeller arc due to airflow-induced lifting forces.
- The corner nails securing the inner belt were inadequate to prevent displacement.
- The use of non-standard conveyor belt matting lacked specific installation, material, or inspection protocols.
- Previous risk assessments and audits failed to recognize the matting as a propeller strike hazard.