ASN Wikibase Occurrence # 296616
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| Date: | Monday 16 September 2002 |
| Time: | 20:35 LT |
| Type: |  Hughes 369D |
| Owner/operator: | Headwest Sky Operations, Inc. |
| Registration: | N500EK |
| MSN: | 1190610D |
| Year of manufacture: | 1979 |
| Total airframe hrs: | 2323 hours |
| Engine model: | Allison 250-C20B |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | O'Neill, Nebraska -
 United States of America
|
| Phase: | Unknown |
| Nature: | Private |
| Departure airport: | Fort Dodge Airport, IA (FOD/KFOD) |
| Ainsworth Airport, NE (ANW/KANW) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The helicopter was substantially damaged during a forced landing following a complete loss of engine power during cruise flight at night. The pilot stated that during the flight, the engine failed, the emergency annunciator lights illuminated, and he felt a yaw due to the loss of full torque. He executed an autorotation to a bean field. The pilot stated that it was very dark and that depth perception was difficult and he flared too soon and "ran out of lift at about 10-12 feet above the ground." The helicopter subsequently impacted the ground. The main rotor blades sheared off the front right upper portion of the cabin and the tailboom. Examination of the engine at the accident site revealed that the N1 rotor system would not rotate. Subsequent examination revealed that the first stage turbine wheel had all of the blades broken off 0.2 to 0.4 inch above the rim at the leading edge and 0.1 to 0.15 inch above the rim at the trailing edge. Scanning electron microscope examination of the fractures revealed no fatigue progression. The fracture surface was oxidized and the macroscopic features were interdendritic, indicating that separation occurred in overload. A metallographic section of one of the blades was made. This section showed a loss of metal as a result of hot corrosion. Distinct spherical particles were observed ahead of the corrosion front, consistent with sulfadation. The chemistry of the spherical particles was found to be rich in sulfur. Examination of the second stage turbine wheel also showed features consistent with hot corrosion damage. Further examination of the submitted items showed that the microstructure, hardness and chemistry conformed to the engineering drawing requirements.
Probable Cause: A loss of engine power due to turbine blade separation as a result of hot corrosion damage to the turbine blades. Contributing to the accident was the pilot misjudging the flare at the completion of the autorotation resulting in a hard landing. The dark night was a factor.
Accident investigation:
 |
|
Sources:
NTSB CHI02LA285
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 14-Oct-2022 08:40 | ASN Update Bot | Added |
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