What happened
On February 19, 2009, a McDonnell Douglas Helicopter 600N, registration N608BP, experienced an engine failure while in cruise flight near San Clemente, California. The helicopter, operated by United States Customs and Border Protection, had departed from Long Beach Airport (Daugherty Field) for Brown Field Municipal Airport in San Diego.
Approximately 30 minutes into the flight, at an altitude of 1,500 feet mean sea level, an 'ECU Degrade' light illuminated on the control panel. The pilot in the right seat took control of the aircraft. Shortly thereafter, the occupants heard an explosion from the rear of the helicopter, followed by multiple warning lights and the sight of flames emitting from the rear.
The pilot initiated an autorotation to land in a parking lot but diverted to an adjacent beach to avoid power lines and the San Onofre Nuclear Generating Station. The helicopter landed hard, semi-submerged in the surf zone. During the landing, a main rotor blade struck and severed the tail boom, and the lower fuselage and skids sustained crush damage. The accident resulted in 2 serious injuries and 1 minor injury; there were no fatalities.
The investigation
Investigators examined the Engine Control Unit (ECU), which revealed various faults, including overspeed, temperature, and FADEC system hard faults.
An examination of the Rolls-Royce 250-C47M engine revealed metallic chips and flakes in the chip detectors. The gas generator and power turbine drive trains could not be rotated manually. Disassembly of the engine showed that the number two bearing retainer ring had dislodged, and much of the bearing's separator cage was missing. Thermal damage was present throughout the entire gas path, affecting turbine blades, wheels, nozzles, and vanes.
Metallurgical analysis of the number two bearing showed extrusion deformation on the inner and outer ring shoulders, which indicated ball excursion. The remaining fragments of the bearing cage exhibited fracture features consistent with fatigue. The engine's logbooks showed the number two bearing had been replaced in 2002 but was not replaced during the engine's 2005 overhaul.