What happened
On January 10, 2010, an AS-350B3 helicopter, registration PP-MAW, was preparing for a flight from Campo de Marte Airport (SBMT) to the UNICID helipad in São Paulo. During the engine acceleration phase from idle to flight power, the pilot encountered significant difficulties in controlling the aircraft, reporting intense vibrations and oscillatory movements.
As the rotor RPM surged, the aircraft entered a state of ground resonance. In an attempt to stabilize the helicopter, the pilot lifted the aircraft into a hover within the ground effect. However, the vibrations persisted, leading the pilot to close the power lever and execute an autorotative landing. While the pilot escaped the aircraft uninjured, the helicopter sustained severe damage, rendering it economically unrepairable.
The investigation
CENIPA's investigation focused on the sequence of engine startup and the pilot's handling of the sudden RPM surge. Investigators examined the operator's organizational structure, noting that the company operated under a shared-ownership model (fractional ownership) that bypassed the more stringent certification requirements of RBAC 135.
The investigation also reviewed the pilot's recent training history, finding that while the pilot was experienced in helicopters generally, they had very limited experience specifically with the AS-350B3 model, having flown the type only 12.5 hours prior to the accident. Furthermore, investigators looked into the company's management of flight training and supervision, as well as the lack of standardized checklists and procedures during the startup sequence.
Findings
- Incorrect startup procedures: The pilot failed to follow the correct sequence of procedures for the AS-350B3, which directly caused the rotor RPM surge.
- Failure to use checklists: The pilot neglected to use the required checklists during the startup phase.
- Insufficient training: The flight instruction provided was non-standardized and lacked the continuity necessary to ensure the pilot could safely operate the specific aircraft type.
- Limited type experience: The pilot had very little flight time in the AS-350B3, and recent operations in different aircraft types hindered the retention of critical knowledge.
- Inadequate management supervision: The operator lacked structured training programs, defined roles, and effective oversight of pilot training and checklist compliance.