Casualties unknown

Hard Landing During Autorotation After Engine Power Loss in Agricultural Helicopter (N43921)

Stockton, CA, US

On August 27, 1990, a Texas Helicopter M47A WASP (registration N43921) was involved in an aviation accident near Stockton, CA. Investigators recorded the probable cause as: The right magneto contact points failed. 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 2026-06-10Data APIEditorial standards

An agricultural helicopter experienced a sudden loss of power shortly after takeoff. The pilot initiated an autorotation but misjudged the flare, resulting in a hard landing and substantial damage. Investigation found failure of the right magneto contact points.

Incident Overview

An agricultural helicopter was involved in an accident during a spraying flight. The pilot had previously landed the helicopter to reload chemicals for another application. Shortly after departing the load site, the pilot heard a loud sound emanating from the engine area, followed by a sudden loss of power and vibration.

Emergency Response

In response to the power loss, the pilot immediately executed an autorotation to an open area. During the descent, the pilot misjudged the flare altitude, leading to a hard landing. The hard landing resulted in substantial damage to the helicopter.

Investigation Findings

A subsequent investigation revealed that the right magneto contact points had failed. This failure was identified as the cause of the engine power loss. No other contributing factors were noted in the source material.

Conclusion

The accident occurred due to a mechanical failure of the magneto, leading to an emergency maneuver that ended in a hard landing. The pilot's actions were in accordance with standard procedures, but the flare misjudgment contributed to the severity of the impact.

Probable cause

The right magneto contact points failed.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001212X24030. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.