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Main Rotor RPM Decay Leads to Loss of Control and Crash of Agricultural Helicopter (N31FG)

Centre, AL, US

On October 9, 1992, a Bell 47G-3B-1 (registration N31FG) operated by Speth, Stephen F. was involved in an aviation accident near Centre, AL. Investigators recorded the probable cause as: THE PILOT'S FAILURE TO MAINTAIN MAIN ROTOR RPM, WHICH RESULTED IN AN IN FLIGHT LOSS OF CONTROL AND COLLISION WITH TERRAIN. 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 2026-07-04Data APIEditorial standards

While performing a turn to reverse direction, an agricultural helicopter pilot allowed main rotor RPM to decay, lost control, and the helicopter crashed after a second RPM decay, severing the tail boom.

Accident Sequence

An agricultural helicopter was involved in an accident while performing a maneuver to reverse direction. During the turn, the pilot allowed the main rotor RPM to decay, resulting in a loss of control. The helicopter subsequently bounced into a field. After becoming airborne again, the RPM decayed a second time, leading to another loss of control. The helicopter then crashed into the field. During the impact, the tail boom was severed by the main rotor blades.

Pilot Report

The pilot reported that there was no mechanical malfunction or failure with the helicopter during the accident flight. The entire sequence was attributed to the pilot's actions during the maneuver.

Loss of control in flight

Frequently asked questions

What happened in the 9 Oct 1992 Bell 47G-3B-1 accident near Centre, AL?

While performing a turn to reverse direction, an agricultural helicopter pilot allowed main rotor RPM to decay, lost control, and the helicopter crashed after a second RPM decay, severing the tail boom.

What aircraft was involved and where did it happen?

The accident on 9 Oct 1992 involved a Bell 47G-3B-1, registration N31FG, operated by Speth, Stephen F., at Centre, AL.

What was the probable cause of the accident?

THE PILOT'S FAILURE TO MAINTAIN MAIN ROTOR RPM, WHICH RESULTED IN AN IN FLIGHT LOSS OF CONTROL AND COLLISION WITH TERRAIN.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X15812. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.