On December 1, 1986, a Bell UH-1B (registration N2770N) was involved in an aviation accident near Calipatria, CA. Investigators recorded the probable cause as: Loss of rotor RPM during initial climb, resulting in loss of directional control and collision with terrain; the reason for the power loss was undetermined. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter experienced a loss of rotor RPM during the initial climb of an aerial application flight, leading to a controlled flight into terrain after the pilot attempted a corrective turn.
What happened
During the initial climb phase at the start of an aerial application mission, the aircraft encountered a sudden drop in rotor RPM. In response to this mechanical anomaly, the pilot initiated a climbing 180-degree right turn intended to reverse direction. The pilot attempted to compensate for the power loss by raising the collective pitch; however, the aircraft subsequently lost directional control. The helicopter collided with the terrain approximately 100 yards from the initial lift-off point.
The investigation
Investigative efforts were unable to determine the specific mechanical or operational reason for the power loss that precipitated the incident. No definitive cause for the rotor RPM drop was identified during the examination of available data.
Findings
The sequence of events indicates that the pilot's attempt to reverse direction while managing a power deficit resulted in a loss of control. The proximity to the takeoff point suggests the aircraft did not gain sufficient altitude to recover from the maneuver.
Probable cause
Loss of rotor RPM during initial climb, resulting in loss of directional control and collision with terrain; the reason for the power loss was undetermined.