What happened
The pilot was conducting a low-level photographic survey of valleys located within mountainous terrain. During this operation, the aircraft entered a narrow valley characterized by steeply rising terrain directly ahead. As the aircraft began to climb sharply, the pilot realized that an excessive rate of climb would be required to clear the obstacles in the path.
In response to this situation, the pilot attempted to execute a steep turn-around while the aircraft was still climbing. This maneuver resulted in a decay of rotor revolutions per minute (RPM). Consequently, the aircraft lost sufficient lift and settled directly into the surrounding trees and brush.
The investigation
The investigation focused on the sequence of events leading to the impact. Key findings included the pilot's decision to attempt a steep turn-around during a sharp climb in confined terrain. The mechanical examination noted the decay of rotor RPM, which was critical to the loss of control and subsequent descent into the vegetation.
Findings
The primary factors contributing to the accident were the operational environment and the pilot's maneuver choice. Flying in mountainous terrain with steeply rising ground limits available options for recovery. The decision to perform a steep turn-around while climbing sharply in a narrow valley created an aerodynamic situation where rotor RPM could not be maintained. This led directly to the aircraft settling into the trees and brush.
Safety message
Pilots conducting low-level operations in mountainous terrain must carefully assess available climb gradients and obstacle clearance margins. Attempting steep turns or maneuvers that require excessive power or result in high descent rates can quickly lead to loss of control, particularly when rotor RPM is critical for maintaining lift.