Accident Details
A pilot performing an aerial application flight in a skid-equipped helicopter reported that the aircraft was within 100 pounds of its maximum gross weight at the time of the accident. While heading south, the pilot executed a left turn to the west. During the turn, the helicopter began to settle with power. The pilot observed low rotor revolutions per minute (RPM) and the helicopter subsequently touched down on soft dirt and rolled over.
Damage
The accident resulted in substantial damage to both rotor drive systems, the fuselage, and the tailboom.
Pilot Statement
In an interview with the National Transportation Safety Board investigator-in-charge, the pilot stated that the helicopter was approximately 20 feet above ground level when the low rotor RPM horn activated and the airspeed was about 20 knots. The pilot recalled that when making the left turn, the helicopter was operating with a tailwind. Additionally, the pilot noted that the hopper design was not approved by the Federal Aviation Administration for jettison.
Mechanical Status
The pilot reported that there were no preaccident mechanical malfunctions or failures with the helicopter that would have precluded normal operation.
Reference Information
The Federal Aviation Administration (FAA) Helicopter Flying Handbook (FAA-8083-21A) discusses factors affecting helicopter performance. According to the handbook, turns increase the load factor, which increases the power required to maintain altitude. Left pedal turns demand additional power from the engine to produce anti-torque from the tail rotor. If the engine cannot supply sufficient power under the prevailing conditions, the helicopter may be unable to sustain altitude. The handbook also notes that strong crosswinds and tailwinds may require more tail rotor thrust, absorbing engine power otherwise available for lift. Weight is another factor; if excess power is not available in certain conditions, a helicopter may descend or need to decelerate to maintain altitude.