ASN Wikibase Occurrence # 133817
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| Date: | Wednesday 20 May 1998 |
| Time: | 05:00 LT |
| Type: |  McDonnell Douglas MD 520N |
| Owner/operator: | Windward Aviation Inc. |
| Registration: | N112HD |
| MSN: | LN008 |
| Year of manufacture: | 1992 |
| Total airframe hrs: | 3861 hours |
| Engine model: | Allison 250-C20R |
| Fatalities: | Fatalities: 0 / Occupants: 5 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | Lanai City, Lanai, HI -
 United States of America
|
| Phase: | En route |
| Nature: | Unknown |
| Departure airport: | Maui, HI (OGG) |
| Lanai City, HI (LNY) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The engine chip light illuminated during cruise and about 10 seconds later the engine out light flickered and then fully illuminated. As the pilot was performing an autorotation he and his passengers heard a loud bang, the helicopter landed on uneven terrain, and subsequently rolled over onto its side. A postcrash fire consumed the helicopter. The third turbine wheel was not located. The fourth turbine wheel was found remote from the helicopter with missing airfoils. In the 5 months prior to the accident, the power turbine had been removed for inspection and repaired several times due to one instance of an N2 lockup and chipped drive splines, and several instances of engine chip light illuminations with high temperatures and turbine rub. In each case, the plugs were removed, inspected per the manufacturer's maintenance manuals, and the oil system flushed. The day before the accident the engine chip light illuminated and the operator found a pasty substance on the chip detector. The chip detector was inspected in accordance with the manufacturer's maintenance manuals and the helicopter was then returned to service. Postaccident disassembly of the engine revealed an oil starvation failure of the No. 5 bearing and a subsequent failure of the No. 3 bearing due to a transfer of the axial loads normally carried by the No. 5 bearing. After the loss of the No. 5 bearing, there was an uncontained overspeed failure of the power turbine rotor to loss of power turbine gear train tooth engagement. Metal debris was encased on the tip of one of the chip detectors. The oil delivery tube that supplies oil to the No. 5 bearing was not recovered and was assumed to have been consumed in the postimpact fire.
Probable Cause: An oil starvation failure of the number 5 bearing for undetermined reasons.
Accident investigation:
 |
|
Sources:
NTSB LAX98LA166
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 27-Feb-2013 13:06 | TB | Updated [Aircraft type, Location, Source, Narrative] |
| 21-Dec-2016 19:26 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 07-Apr-2024 12:18 | ASN Update Bot | Updated [Time, Other fatalities, Departure airport, Destination airport, Source, Narrative, Category, Accident report] |
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