N225MLRobinson Helicopter R44 · 2007

On August 3, 2024, about 1415 central daylight time, a Robinson R44 helicopter, N225ML, sustained substantial damage when it was involved in an accident near Bryant, Iowa. The pilot was not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 137 aerial application flight.

Before departure, the helicopter was loaded with about 7 gallons of 100 low lead fuel and about 45 gallons of mixed liquid product to apply to a corn field. After takeoff from a load truck, the pilot noticed a drop in rotor rpm. The pilot followed an area of terrain that sloped downward in an attempt to gain airspeed. The pilot attempted to increase rotor rpm but was unsuccessful. The pilot flared the helicopter while attempting to land; however, the helicopter impacted an area of rising terrain and came to rest on its left side. The pilot was able to egress from the helicopter without further incident.

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. The inspector found no clear indication of a pre-impact malfunction or failure with the helicopter that would have precluded normal operation.

According to maintenance records, the last annual inspection was completed on June 15, 2024. On August 1, 2024, 2 days before the accident, a new governor motor was installed. The helicopter had operated for about 12 hours since the installation of the new governor motor.

The governor system, consisting of 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 a protective tubing installed and the wires were improperly routed through the points compartment. Although the wires were improperly routed, no damage was found to the wires and the magneto functioned normally when tested. No failures or malfunctions with the governor system were found.

The closest weather reporting facility to the accident site was from Clinton Municipal Airport (CWI), Clinton, Iowa, located 8 miles south of the accident site. The CWI automated weather observation station at the time of the accident recorded wind from 230 degrees at 4 knots, 10 statute miles visibility, clear sky conditions, a temperature of 30°C, dew point temperature of 22°C, and a barometric pressure of 29.97 inches of mercury. The airport elevation was 707 ft mean sea level (msl). Density altitude was calculated to be 2,883 ft msl.

According to the carburetor ice probability chart, the atmospheric conditions at the time of the accident 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 recorded the engine’s cylinder head temperature and exhaust gas temperature. A review of the data found no explanation for the loss of engine power.