What happened
On December 3, 2021, a Robinson R44 II helicopter, registration PR-IUG, was performing an agricultural spraying mission over a cornfield at Fazenda Jacarundá, in Santo Antônio do Amparo, Minas Gerais. The aircraft was operated by Flygreen Aero Agrícola Serviços Aéreos Especializados.
Shortly after departing for its fourth flight of the day, the aircraft began to experience lateral vibrations and an immediate loss of engine power while the pilot was maneuvering to position for the application. Due to the low altitude, the pilot was unable to return to the takeoff site or find an alternative safe landing area. The pilot attempted an autorotation procedure, but the helicopter impacted the ground and overturned to the right. The pilot sustained minor injuries, while the aircraft suffered substantial damage.
The investigation
CENIPA investigators examined the Lycoming IO-540-AE1A5 engine to determine the cause of the power loss. While the ignition system and spark plugs appeared functional, testing revealed significantly low compression in cylinder 5. Upon disassembly, investigators found corrosion and carbon deposits on the exhaust valve seat and head.
Further inspection of the fuel system revealed oxidation within the fuel distributor and the lower chamber of the fuel pump. Crucially, a contaminant liquid was found in both the fuel pump and the servojector. Laboratory analysis of this liquid confirmed the presence of water, proving that the fuel had been contaminated.
Findings
- The engine failure was caused by fuel contamination with water.
- The aircraft was within its maximum takeoff weight and balance limits during the flight.
- The pilot was properly licensed, qualified, and met all medical requirements.
- Although the aircraft's airworthiness certificate was valid, the engine and airframe logbooks were not up to date.
- The operator's refueling logistics had previously involved reports of fuel with unusual coloration, which were noted by personnel but not investigated.
- Management planning and supervision failed to implement corrective actions to identify the source of the contamination or prevent its use in flight operations.