Casualties unknown

1990-04-04: Bell 47G (N739B) — Airborne Helicopters — LA Verne, CA

LA Verne, CA, US

On April 4, 1990, a Bell 47G (registration N739B) operated by Airborne Helicopters was involved in an aviation accident near LA Verne, CA. Investigators recorded the probable cause as: THE HELICOPTER'S ROTOR SYSTEM BEING ALLOWED TO UNDERSPEED AS A RESULT OF IMPROPER USE OF FLIGHT CONTROLS BY THE DUAL STUDENT; IMPROPER SUPERVISION BY THE CERTIFIED FLIGHT INSTRUCTOR; AND DELAYED REMEDIAL ACTION BY THE CERTIFIED FLIGHT INSTRUCTOR WHICH ALLOWED… 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 conducting a power recovery autorotation training exercise collided with the runway after the rotor RPM decayed when power was applied. The instructor pilot was late in taking controls.

Incident Overview

During a training flight, a helicopter collided with the runway while executing a power recovery autorotation. The instructor pilot reported that the aircraft began to vibrate as the maneuver was terminated. The commercially rated student pilot applied power, and the engine responded, but the rotor RPM decayed. The helicopter then struck the runway.

Instructor Actions

The instructor pilot acknowledged being late in taking control of the aircraft and initiating recovery procedures. No further details regarding the instructor's actions were provided.

Post-Accident Examination

An FAA airworthiness inspector examined the helicopter following the accident. The inspection revealed no pre-impact mechanical malfunctions or failures. The aircraft's systems were found to be functional up to the point of impact.

Training Context

The accident occurred during a training maneuver known as a power recovery autorotation, a procedure used to simulate engine failure and practice recovery. The specific type of helicopter, its registration, and the location were not disclosed in the investigation source.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001212X22944. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.