Engine Bearing Failure Leads to Bell 407 Emergency Landing and Severe Damage

Casualties unknown • nahe Hofgeismar, DE

A sudden loss of engine power caused by a bearing failure forced a Bell 407 into an emergency landing in a field near Hofgeismar, resulting in significant aircraft damage.

What happened

On June 26, 2016, a Bell 407 helicopter was performing a ferry flight from Assen, Netherlands, to Ingolstadt-Manching, Germany, with a planned refueling stop at Kassel-Calden. While flying near Hofgeismar, the pilot experienced torque fluctuations in the controls and a drop in the main rotor speed (Nr) to approximately 94%.

In response to the power loss, the pilot initiated an autorotation and selected a suitable field for an emergency landing. During the approach, the pilot successfully cleared an overhead power line. However, as the helicopter slid across a sloping field with high vegetation, the deceleration caused the aircraft to pitch forward. To prevent a forward tip-over, the pilot applied aft cyclic input, which caused the main rotor to strike the tail boom. The impact resulted in severe damage to the aircraft, including damage to the rotor head, the separation of the tail boom, and the loss of the tail rotor and vertical fins.

The pilot, who was highly experienced with over 5,00 and hours of total flight time, exited the aircraft uninjured. After the aircraft came to a stop, the pilot noted the engine was still running at reduced power and manually shut it down.

The investigation

The BFU investigation focused on the engine's Rolls-Royce M250-C47B turboshaft. While the engine's electronic control unit (ECU) did not record any hard faults or parameter exceedances—likely due to the pilot's rapid response—investigators found a damaged N2 speed sensor.

Upon disassembly of the engine, investigators identified significant damage to the No. 5 bearing. The investigation included a detailed analysis by the engine manufacturer in the United States. Findings revealed that the No. 5 bearing separator and several holding rings had fractured. Metal shavings were also discovered in the engine's chip detectors and oil filter.

Probable cause

The accident was caused by a failure of the No. 5 bearing in the engine, which led to a sudden loss of power and necessitated an emergency landing. The subsequent impact of the main rotor with the tail boom was caused by the pilot's attempt to prevent a forward tip-over during the landing roll through high vegetation.

Frequently asked questions

What happened in the 2016-06-26 Bell Helicopter Textron Bell 407 accident near nahe Hofgeismar, DE?

A sudden loss of engine power caused by a bearing failure forced a Bell 407 into an emergency landing in a field near Hofgeismar, resulting in significant aircraft damage.

What aircraft was involved and where did it happen?

The accident on 2016-06-26 involved a Bell Helicopter Textron Bell 407, at nahe Hofgeismar, DE.

What was the probable cause of the accident?

The accident was caused by a failure of the No. 5 bearing in the engine, which led to a sudden loss of power and necessitated an emergency landing. The subsequent impact of the main rotor with the tail boom was caused by the pilot's attempt to prevent a forward tip-over during the landing roll through high vegetation.

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