On August 1, 1984, a Bell 47G-5A (registration N4099G) was involved in an aviation accident near Winterhaven, CA. Investigators recorded the probable cause as: The pilot inadvertently allowed the rotor RPM to decay. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
After loading with 60 gallons of pesticide, a pilot began takeoff. The aircraft became airborne, traveled about 300 feet, then rotor RPM decayed, causing descent. The left skid dug into soft soil, pitching the aircraft forward; it came to rest upright.
Accident Details
The accident occurred during a takeoff attempt. According to the pilot, the aircraft was loaded with 60 gallons of pesticide before takeoff was initiated. The aircraft became airborne and traveled approximately 300 feet when the pilot inadvertently allowed the rotor RPM to decay, causing the aircraft to descend.
Impact Sequence
Prior to impact, the pilot attempted to regain rotor RPM but was unsuccessful. The left skid dug into soft soil, causing the aircraft to pitch forward. The aircraft then came to rest in an upright position.
Findings
The investigation determined that the pilot inadvertently allowed the rotor RPM to decay during the takeoff climb. The aircraft's left skid contacting soft soil contributed to the forward pitch upon impact.
Probable cause
The pilot inadvertently allowed the rotor RPM to decay.