What happened
On April 6, 1996, an AS 350 B2 helicopter, registration PP-EPM, operated by the Military Police of Minas Gerais, was performing a flight check for a flight instructor qualification. The flight involved two missions; while the first proceeded normally, the second mission involved training for emergency procedures, specifically a simulated hydraulic failure.
During the maneuver, the hydraulic system was intentionally deactivated. As the aircraft approached a hover, the pilot experienced unusually heavy flight controls. The pilot did not communicate these difficulties to the checker (the instructor on board). While attempting to maintain control during the hover, the pilot applied power, which led to a loss of control. The aircraft entered a 360-degree spin with the tail low to the ground, eventually striking the terrain with the main rotor at a 30-degree angle. The impact caused severe damage to the engine, transmission, rotors, and airframe.
The investigation
CENIPA investigators examined the flight profiles, the crew's training backgrounds, and the aircraft's maintenance history. The investigation focused on the lack of specific training for the pilot regarding left-seat operations and instructor qualification. Investigators also looked into the ergonomic differences between the left and right pilot controls, noting that the left-side collective grip is smoother and thinner, which may have been harder to manipulate without gloves in the high temperatures. While hydraulic component tests performed on a test bench showed normal operation, the investigation noted that no analysis of hydraulic fluid contamination had been conducted following the accident.
Findings
- Deficient Crew Resource Management (CRM): The pilot failed to communicate the abnormal control heaviness to the checker, and the checker failed to intervene or maintain active communication.
- Inadequate Training: The pilot had not received specific instruction for left-seat operations or instructor-level training, and the organization lacked a formal program for instructor formation.
- Operational Planning: The flight profile involved a hover maneuver that, while possible, increased risk compared to the manufacturer-recommended running landing approach.
- Psychological Factors: The pilot experienced high levels of anxiety due to the pressure of the qualification check, which contributed to complacency and poor decision-making.
- Human Factors: The pilot was not wearing flight gloves, which, combined with high temperatures and sweat, may have hindered control of the smooth left-side collective grip.