Accident Narrative
On August 3, 2024, at about 1415 central daylight time, a Robinson R44 helicopter, registration N225ML, sustained substantial damage during an accident near Bryant, Iowa. The helicopter was being operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight. The pilot, the sole occupant, was not injured.
Before departure, the helicopter was loaded with approximately 7 gallons of 100 low lead fuel and about 45 gallons of mixed liquid product intended for application on a corn field. After takeoff from a load truck, the pilot noticed a drop in rotor rpm. The pilot followed terrain that sloped downward in an attempt to gain airspeed. Despite efforts to increase rotor rpm, the pilot was unsuccessful. The pilot flared the helicopter while attempting to land, but the helicopter impacted rising terrain and came to rest on its left side. The pilot was able to egress without further incident.
Aircraft Damage and Examination
The helicopter sustained substantial damage to the fuselage, main rotor system, tail cone, and tail rotor system. An inspector from the Federal Aviation Administration examined the helicopter and engine and found no clear indication of a pre-impact malfunction or failure that would have precluded normal operation.
Maintenance and Component Testing
According to maintenance records, the last annual inspection was completed on June 15, 2024. On August 1, 2024, two days before the accident, a new governor motor was installed. The helicopter had operated for about 12 hours since the installation. The governor system, including the governor controller, governor motor, and the engine’s right magneto, were shipped to the airframe manufacturer for testing. The components were attached to a test bench. The magneto was tested at various speeds with no anomalies noted. The tachometer wires in the magneto had protective tubing installed but were found to be improperly routed through the points compartment. However, no damage was found to the wires, and the magneto functioned normally when tested. No failures or malfunctions with the governor system were found.
Weather Conditions and Engine Data
The closest weather reporting facility was Clinton Municipal Airport (CWI), Clinton, Iowa, located 8 miles south of the accident site. At the time of the accident, the automated weather observation station recorded wind from 230 degrees at 4 knots, visibility 10 statute miles, clear sky conditions, temperature 30°C, dew point 22°C, and barometric pressure 29.97 inches of mercury. The airport elevation was 707 feet mean sea level, and the calculated density altitude was 2,883 feet msl. According to the carburetor ice probability chart, atmospheric conditions were conducive to serious icing at glide power; however, the reported loss of engine power occurred while at takeoff power. A device capable of recording engine data captured cylinder head temperature and exhaust gas temperature. A review of the data found no explanation for the loss of engine power.