What happened
On November 24, 1997, an AS-365N1 helicopter, registration PP-ELB, was undergoing a maintenance ground run at the Heliponto da Lagoa in Rio de Janeiro, Brazil. The operation was intended to verify the blade balance following the replacement of frequency adapters on the main rotor hubs.
During the startup of engine number one, as the engine accelerated from 40% to 70% NG, the aircraft's struts began to extend, and the helicopter gained lift. The aircraft then initiated a left longitudinal roll. Upon noticing the lateral tilt, the pilot immediately shut down the engine. However, due to inertia, the helicopter continued its leftward movement, eventually tilting sideways and causing the main rotor blades to strike the ground. The impact resulted in widespread severe damage, rendering the main rotor blades and the horizontal stabilizer unrecoverable. No injuries were reported among the pilot or the three mechanics present outside the aircraft.
The investigation
CENIPA investigators examined the aircraft's maintenance history, the pilot's experience, and performed flight tests using a similar aircraft. The investigation revealed that the pilot had only 43 hours of experience in this specific aircraft type. While the pilot's licenses and medical certificates were valid, the investigation noted that the pilot had performed a test flight in the same aircraft just one week prior, which had identified abnormal vibrations.
Tests conducted with a similar helicopter established that if the collective is unlocked and positioned at +2.5 units, the aircraft tends to extend its struts and roll to the left during engine acceleration. The investigation also found that the collective lever was found in the unlocked position following the accident. Furthermore, the investigation highlighted organizational issues within the Coordenadoria Geral de Operações Aéreas (CGOA), noting a lack of unified organizational culture and standardized procedures due to the integration of various different state agencies.
Findings
- Failure to verify the collective lock: Evidence suggests the pilot failed to perform the pre-flight checklist, specifically neglecting to verify that the collective was in the locked position.
- Improper emergency response: Instead of applying right cyclic and lowering the collective to stabilize the aircraft, the pilot performed an engine shutdown, which allowed the roll to continue.
- Inadequate supervision: The mission was authorized for a pilot with limited experience in the specific aircraft type, despite more experienced pilots being available.
- Organizational deficiencies: A lack of standardized procedures and a fragmented organizational culture contributed to the occurrence of errors in both decision-making and execution.
Safety action
CENIPA issued the following recommendations to the Coordenadoria Geral de Operações Aérea (CGOA):
- Establish defined criteria for the recruitment, selection, training, and development of human resources.
- Establish specific criteria for conducting maintenance test flights.
- Develop an Aircraft Accident Prevention Program (PPAA) to define procedures and responsibilities for aeronautical emergencies at the Heliponto da Lagoa.