Accident Overview
On 21 September 2024, at approximately 11:57 am local time, a Bell 206B helicopter (registration N206BH) took off from the roof of a house in Cacique, Monción, Santiago Rodríguez, Dominican Republic. The flight was conducted under visual flight rules (VFR) with a planned destination of La Caya, carrying two occupants: a pilot and a passenger. During the initial climb, the engine suffered a complete loss of power. The pilot reported hearing a loud bang followed immediately by the power loss. With no engine power, the pilot executed an autorotational descent, landing on a cliff characteristic of the local terrain. Upon touchdown, the helicopter impacted the ground and rolled down the hillside, turning over several times before coming to rest inverted in dense vegetation. The pilot observed a small fire in the engine exhaust duct, which he extinguished with the onboard fire extinguisher. Both occupants evacuated the aircraft without injuries.
Aircraft and Engine Details
The helicopter involved was a Bell 206B, serial number 4179, manufactured in 1991. It was powered by a single Rolls-Royce 250-C20J turboshaft engine (serial number CAE270558). The aircraft had accumulated 2,647.4 total flight hours, with the same hours on the engine. The last inspection was conducted on 7 March 2023. The helicopter was equipped for five seats and used Jet-A1 fuel. The owner/operator was listed as private.
Investigation Findings
The engine was inspected at the accident site while still installed. Checks included engine mounts, exhaust collector oil, hardware torque, air control tubes, engine compartment, power turbine (N2), fourth-stage power turbine blades, compressor (N1), rotational witnesses, control continuity, and fuel control unit (FCU) and power turbine governor (PTC). The fuel supply line to the injector contained approximately one teaspoon of clean, clear fuel with no visible particles or water. A fuel sample from the airframe fuel filter was clean and showed no water traces; the filter contained a small amount of unidentified soft material. The injector face showed normal carbon soot with no anomalies. However, upon disassembly, the injector filter was found completely covered by a semi-transparent gel-like substance. No evidence of mechanical failure or malfunction was found in the engine. All indications point to fuel contamination, which resulted in the formation of a semi-transparent gel that restricted fuel flow through the injector filter, ultimately causing a loss of engine power due to fuel starvation.
Probable Cause
The probable cause of the accident was fuel contamination leading to the formation of a semi-transparent gel that blocked the injector filter, restricting fuel flow and resulting in a total loss of engine power.