What happened
On August 21, 2013, an EC120B helicopter, registration PR-IVE, was conducting a local maintenance flight near Campo de Marte Aerodrome in São Paulo, Brazil. While flying at approximately 1,200 feet above the ground, the pilot observed the low engine oil pressure light illuminate.
Following the engine failure, the pilot declared an emergency and initiated an autorotation procedure to land on the right side of the Marginal Tietê. During the flare maneuver, the tail of the aircraft collided with a concrete wall, causing the tail cone to rupture and resulting in substantial damage to the main rotor blades and the airframe. Despite the impact, the two occupants on board escaped without injury.
The investigation
CENIPA investigators and representatives from the French BEA examined the Arrius 2F engine to determine the cause of the oil pressure drop. The investigation focused on the lubrication system and the internal components of the engine modules.
Technical analysis revealed that the reduction gear train of the Reduction Gearbox Module (M01) had seized. Upon inspecting the lubrication system, investigators found a significant amount of metallic particles within the magnetic plugs and the crankcase. While the oil pump and filters appeared functional, the examination of the Gas Generator and Power Turbine (M02) showed evidence of extreme thermal distress. Specifically, the front bearing roller tracks exhibited discoloration and deformation, and the rear bearing showed signs of friction and carbonization. Furthermore, the centrifugal compressor cover showed evidence of overtemperature caused by contact with the impeller blades.
Findings
- The engine experienced a rupture of the lubricating oil film, leading to extreme overtemperature (reaching 1,034°C).
- The loss of lubrication caused the deterioration of the gas generator bearings, which subsequently led to the seizing of the gas generator and the reduction gear train.
- The engine failure in flight was the direct cause of the emergency landing.
- The collision with the concrete wall during the flare was the cause of the tail cone rupture.
- Maintenance records for the airframe and engine were noted to be outdated.
- The exact root cause of the initial loss of oil pressure could not be definitively identified, though maintenance services performed on the aircraft could not be excluded as a contributing factor.