ASN Wikibase Occurrence # 145041
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| Date: | Saturday 14 April 2012 |
| Time: | 02:55 |
| Type: |  Bell 407 |
| Owner/operator: | Med-trans Corp |
| Registration: | N509MT |
| MSN: | 53281 |
| Year of manufacture: | 1998 |
| Total airframe hrs: | 7379 hours |
| Engine model: | Rolls-Royce 250-C47B |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | near Aberdeen, SD -
 United States of America
|
| Phase: | En route |
| Nature: | Ferry/positioning |
| Departure airport: | Aberdeen, SD (KABR) |
| Aberdeen, SD (SD54) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The pilot reported that, shortly after departure, the helicopter yawed left and that he heard a “loud howling/grinding sound” emanating from the upper area of the helicopter. He subsequently reduced power and performed a minimum power descent to an open area. During the landing, the helicopter touched down hard. A postimpact examination of the engine found that two third-stage turbine wheel blades had cracked and separated due to high-cycle fatigue at the trailing edge during operation of one or more natural frequencies of the wheel. Four additional blades displayed fatigue cracks. Metallurgy examinations revealed that the blades had no evidence of material anomalies and met the material hardness and composition specifications. The observed high-cycle fatigue initiation and propagation characteristics were consistent with operating in a condition conducive to vibration. The engine manufacturer plans to release design changes that will increase the operating speed natural frequency margin and improve the vibration margin.
Probable Cause: The fatigue failure of two turbine engine blades due to vibration.
Accident investigation:
 |
|
Sources:
NTSB
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=509MT
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 14-Apr-2012 12:13 | gerard57 | Added |
| 14-Apr-2012 20:44 | Geno | Updated [Time, Aircraft type, Registration, Cn, Operator, Location, Destination airport, Source, Narrative] |
| 17-Apr-2012 09:15 | Geno | Updated [Registration, Cn, Operator, Source] |
| 04-May-2012 23:30 | Geno | Updated [Time, Operator, Departure airport, Source] |
| 28-Jul-2013 16:30 | TB | Updated [Operator, Location, Source, Narrative] |
| 31-Aug-2014 18:23 | Aerossurance | Updated [Narrative] |
| 21-Dec-2016 19:28 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 27-Nov-2017 20:37 | ASN Update Bot | Updated [Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative] |
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