NTSB Identification: LAX02GA209.
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Accident occurred Tuesday, June 25, 2002 in Ontario, CA
Probable Cause Approval Date: 06/08/2005
Aircraft: McDonnell Douglas 369E, registration: N40NT
Injuries: 2 Serious.
: NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this public aircraft accident report.
The helicopter landed hard during an autorotation following a catastrophic engine failure in the takeoff initial climb. The engine lost all power during the initial climb out on a test flight following the completion of a 100-hour inspection. The pilot initiated an autorotative descent. While he maneuvered to avoid automobile traffic and power lines, the main rotor rpm decayed. The helicopter touched down hard on a street and was destroyed by an intense fuel-fed ground fire. The accident occurred during the first flight following maintenance performed by the on-board passenger, a mechanic employed by the operator. The helicopter's airframe was examined and no evidence of preimpact anomalies were found. Upon splitting the engine's case halves, all of the compressor blades on stages 1 through 6 were found either damaged or missing. A piece of a wire tie wrap was noted adhering to one of the case halves in the 6th stage area. Additionally, metallic debris was found in the outer combustion case (OCC). The metallurgical examination of the OCC debris revealed it was composed of an aluminum-magnesium-silicon alloy, which was foreign to components used in the engine. Wire tie wraps, similar to the tie wrap found in the engine, were also found in the accident site debris field. Similar wire tie wraps were additionally observed in storage at the operator's maintenance facility. The air intake to the engine's compressor is enclosed in a plenum chamber on the top of the helicopter. Prior to the accident, the mechanic had been observed performing maintenance in this area.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The mechanic's improper maintenance procedures (FOD prevention) during a 100-hour inspection, which resulted in foreign object damage (FOD) to the compressor section and catastrophic engine failure. Factors were the presence of vehicles and power lines partially obstructing the forced landing site that necessitated the pilot's use of rotor system energy to avoid, which resulted in a hard landing. Full narrative available
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