What aircraft was involved and where did it happen?

The accident on 2001-02-23 involved a aircraft, registration PTYUM, at SÃO GONÇALO, RJ, BR.

What was the probable cause of the accident?

The engine power loss was likely caused by contaminated fuel containing water or a systemic FADEC failure, compounded by the pilot's failure to follow manual procedures and the violation of minimum altitude requirements.

Engine Power Loss Leads to Hard Landing in Bell 407

A Bell 407 helicopter experienced engine power loss and FADEC failure during a low-altitude flight in São Gonçalo, Brazil, resulting in a heavy impact and pilot injury.

What happened

On February 23, 2001, a Bell 407 helicopter, registration PT-YUM, was conducting a sightseeing flight over the São Gonçalo region in Rio de Janeiro. The aircraft was carrying the local mayor, the secretary of public works, and the municipal security chief. While flying over a densely populated area at an altitude of approximately 350 feet, the aircraft experienced a sudden loss of engine power. This was accompanied by the activation of "FADEC DEGRADE" and "FADEC FAIL" warning lights on the instrument panel.

Due to the low altitude, the pilot immediately initiated an autorotation procedure to attempt an emergency landing in a nearby clearing. The resulting impact with the uneven terrain was extremely violent, with an estimated deceleration of approximately 10G. The landing caused significant damage to the aircraft's skids and upper structure. The pilot sustained a spinal injury, while the three passengers remained uninjured.

The investigation

The CENIPA investigation focused on the cause of the engine power loss and the pilot's emergency response. Technical examinations of the Allison 250-C47B engine components, specifically the Electronic Control Unit (ECU) and the Hydromechanical Unit (HMU), did not reveal isolated mechanical or electronic failures. However, incident recorder data showed turbine speed fluctuations ten seconds prior to the failure, which affected fuel control and triggered the FADEC system to revert to manual mode.

Investigators also analyzed the fuel quality and found that the fuel sample contained visible water at the bottom of the container, meaning the fuel did not meet required regulatory standards. Additionally, the investigation examined the pilot's flight altitude and adherence to established emergency procedures.

Findings

The primary contributing factor was improper judgment regarding emergency procedures; the pilot failed to press the FADEC MODE circuit breaker to confirm the transfer to manual control as prescribed by the manual.
The pilot's flight altitude of 350 feet violated air traffic regulations (ICA 100-4), which require a minimum of 500 feet over populated areas. This low altitude left insufficient time to execute all necessary autorotation procedures.
There was evidence of flight indiscipline regarding altitude minimums.
The presence of water in the fuel was a significant factor, and a lack of effective supervision during the refueling process may have allowed contaminated fuel to be used.
The engine failure may have been caused by a systemic issue within the FADEC system (such as wiring, environmental contamination, or electromagnetic interference) that could not be detected through isolated component testing.