Bell 206 N61KH accident near Greenville, Illinois

Probable cause

The mechanic’s failure to inspect and clean the entire fuel nozzle assembly in accordance with the engine maintenance manual, which resulted in fuel starvation and a partial loss of engine power, an autorotation, and a hard landing.

NTSB analysis

The pilot of the aerial application helicopter completed operations for the day and stopped to refuel on the way back to the operator’s facility. After refueling and during the initial climb, the pilot reported that he was unable to maintain main rotor rpm. The pilot initiated a 180° autorotation and landed hard on a grass area near a hangar. During the landing, the right-side skid collapsed, the tail boom separated, and the helicopter came to rest upright. The helicopter sustained substantial damage to the fuselage, the tail boom, and the tail rotor system.

Examination of the engine revealed that the fuel nozzle inlet screen was contaminated and partially blocked with a buildup of debris. The fuel nozzle assembly had been inspected, as part of the required 150-hour inspection interval, 25.9 hours before the accident.

The director of maintenance (DOM) for the operator was interviewed for additional details on how the inspection had been performed. The DOM reported that he had cleaned the fuel nozzle, but not the fuel nozzle inlet screen. When asked specifically about the fuel nozzle inlet screen cleaning, the DOM reported that he, “has not had a chance to get to that yet.” A review of the engine maintenance records showed that the DOM had signed his initials indicating that the fuel nozzle assembly was inspected and cleaned at the required 150-hour inspection interval.

The partially blocked fuel nozzle inlet screen with debris likely restricted fuel flow to the engine. The DOM’s failure to clean the entire fuel nozzle assembly, including the fuel nozzle inlet screen, likely resulted in a partial loss of engine power, an autorotation, and a hard landing. Based on the available evidence, it is likely the DOM did not clean the fuel nozzle inlet screen for undetermined reasons.

Text from the NTSB. Open the NTSB docket for CEN23LA025 for the full record.