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Helicopter Rotor RPM Loss During Aerial Application Climb (N2770N)

Calipatria, CA, US

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.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-20Data APIEditorial standards

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.

Frequently asked questions

What happened in the 1 Dec 1986 Bell UH-1B accident near Calipatria, CA?

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 aircraft was involved and where did it happen?

The accident on 1 Dec 1986 involved a Bell UH-1B, registration N2770N, at Calipatria, CA.

What was the probable cause of the accident?

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.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001213X35372. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.