What happened
On May 8, 2013, an HB-350B helicopter, registration PT-HML, was performing a scheduled panoramic flight service near Rio de Janeiro. The flight, operated by Helisul Air Taxi Ltd., carried one pilot and five passengers. The aircraft departed from the Morro da Urca helipad for a brief seven-minute excursion.
During the final approach to the Morro da Urca helipad, the aircraft experienced a sudden loss of lift and a significant increase in the rate of descent. The pilot attempted to compensate by increasing power via the collective; however, the aircraft continued to sink and entered a downward turn to the left. The helicopter eventually struck a forested area approximately eight meters short of the helipad. Despite the substantial damage to the main rotor, tail cone, and tail rotor, all six occupants escaped the accident unharmed.
The investigation
CENIPA investigators examined the flight path, meteorological data, and the aircraft's mechanical state. The investigation established that the aircraft was within weight and balance limits and that the pilot was fully qualified with a valid medical certificate. While the airframe and engine logbook records were noted as not being updated, no mechanical failures were identified as the primary cause.
Investigators analyzed the approach trajectory, which was required to be parallel to the Sugar Loaf cable car lines due to a regulatory agreement (TAC) intended to avoid overflight of the Urca district. The investigation also looked into the wind conditions, noting that the pilot relied on meteorological data from Santos Dumont Aerodrome (SBRJ), which differed from the actual conditions at the helipad due to the distance and local obstacles.
Findings
- Vortex Stall: The approach with an excessive rate of descent may have initiated a vortex stall of the main rotor blades. The pilot's attempt to recover by increasing collective likely aggravated the situation by further increasing the angle of attack.
- Meteorological Uncertainty: The lack of accurate, real-time wind direction and intensity information at the Morro da Urca helipad meant the pilot was operating based on distant data, which may have resulted in a tailwind approach, contributing to the vortex stall condition.
- Operational Pressure: Managerial decisions and regulatory constraints (the TAC) may have diverted the pilot's attention from critical performance and meteorological factors toward the necessity of maintaining a specific approach path to avoid neighborhood overflight restrictions.
- Infrastructure Limitations: Local wind indicators were potentially unreliable due to interference from nearby antennas, preventing the pilot from accurately assessing the wind at the landing site.