Bell 407 N407HC accident near Columbia, Maryland

Probable cause

The short circuit failure of a tantalum capacitor, internal to the engine’s electronic control unit, resulting in an uncommanded shutdown of the engine in flight.

NTSB analysis

During a routine police patrol flight, while about 600 feet above the ground, the helicopter suddenly yawed to the left and the red "ENGINE OUT" warning light illuminated. The engine lost all power and the pilot performed an autorotation landing on a nearby football field. While avoiding obstacles, the helicopter landed hard, resulting in substantial damage to the airframe. A postaccident examination of the engine revealed no damage or obvious reason for the loss of power.

The engine's electronic control unit (ECU) was removed and was shipped to the manufacturer's facility for evaluation and testing. The examination of the ECU revealed that the engine was operating normally until an unexpected activation of the full authority digital electronic control overspeed protection system fuel reduction solenoid, which is internal to the ECU, resulting in an uncommanded in-flight engine shutdown. A subsequent ECU functional review confirmed that a short circuit failure of a tantalum capacitor was the source of the ECU malfunction. After the accident, Bell Helicopter issued an Alert Service Bulletin and Rolls-Royce issued an accompanying Commercial Engine Bulletin that included the installation of an overspeed adapter to reduce the likelihood of a false overspeed activation.

Text from the NTSB. Open the NTSB docket for ERA13TA261 for the full record.