Incident Description
On 27 May 2002, at 07:30 UTC, a Schweizer S 269C helicopter, registration I-GUAN, operated by Elisystem s.r.l., was engaged in aerial work over Caresana, Vercelli province, Italy. The flight involved the spreading of substances for anti-larval treatment of rice fields. While flying at an altitude of approximately 6 meters in translational flight, the pilot perceived strong vibrations emanating from the tail rotor. As a precautionary measure, the pilot decided to perform an off-field landing. After landing, an inspection revealed a fracture of the tip cap on one of the tail rotor blades.
Aircraft and Crew Information
The Schweizer S 269C is a single-engine helicopter with a maximum takeoff weight of 930 kg. Its length is 9.40 m, height 2.66 m, and main rotor diameter 8.18 m. The aircraft was owned and operated by Elisystem s.r.l. based in Rivanazzano, Pavia.
The pilot, a 30-year-old Italian male, held a valid commercial helicopter pilot license and a valid medical certificate. He had accumulated 628 total flight hours, with approximately 616 hours on the S 269C type. In the preceding 30 days, he had flown 38 hours and 43 minutes, with 18 hours and 40 minutes in the last 7 days, and no flight time in the last 24 hours.
Weather Conditions
At the time of the incident, weather conditions were reported as visibility greater than 10 km, no wind, and 6/8 cloud cover.
Analysis
A detailed analysis conducted on the affected tail rotor blade indicated that the breakage of the tip cap was likely caused by the detachment of resin fillets securing the basal tip during operation. Centrifugal force would have projected the loose resin material toward the blade tip, resulting in the fracture of the cap. Additionally, the blade showed evidence of strong deformation, predominantly elastic, characterized by fracture and partial detachment of paint along the entire trailing edge and partial laminate rupture. This deformation was attributed to a significant stress applied in a posterior-anterior direction, likely resulting from an impact. The investigation could not determine whether the impact occurred prior to or after the detachment of the resin fillets.
Probable Cause
The investigation concluded that the detachment of the tail rotor blade tip was due to a technical factor, probably caused by a strong stress.