Casualties unknown

1990-07-31: Bell 47G3B1 (N4990H) — Coon Rapids, MN

Coon Rapids, MN, US

On July 31, 1990, a Bell 47G3B1 (registration N4990H) was involved in an aviation accident near Coon Rapids, MN. Investigators recorded the probable cause as: The pilot's failure to maintain adequate fuel supply, which led to engine power loss and a subsequent hard landing during an attempted autorotation. 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 1781061362Data APIEditorial standards

A helicopter suffered total engine failure in flight, leading to a hard landing after the pilot attempted an autorotation with insufficient altitude.

What happened

The aircraft was operating in normal cruise flight when it experienced a complete loss of engine power. In response to the emergency, the pilot initiated an autorotational descent to land. However, the pilot misjudged the timing and height of the flare maneuver during the final phase of the landing. This error resulted in a hard impact with the ground, causing substantial damage to the airframe.

The investigation

Following the accident, investigators examined the helicopter's systems and fuel state. The inspection revealed that there was only unusable fuel remaining in the tanks at the time of the incident. To verify the mechanical integrity of the powerplant, fuel was added to the tanks after recovery. Upon refueling, the engine operated normally, confirming that the failure was not due to a mechanical malfunction but rather a lack of available fuel.

Findings

The primary factor contributing to the accident was the depletion of usable fuel during flight. The subsequent hard landing and substantial damage were direct consequences of the pilot's inability to execute a safe autorotation due to insufficient altitude or misjudgment of the flare point.

Probable cause

The pilot's failure to maintain adequate fuel supply, which led to engine power loss and a subsequent hard landing during an attempted autorotation.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001212X23621. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.