ASN Wikibase Occurrence # 39234
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| Date: | Saturday 13 July 1996 |
| Time: | 13:25 |
| Type: |  Sikorsky CH-54A (S-64A) |
| Owner/operator: | Silver Bay Logging Company |
| Registration: | N541SB |
| MSN: | 64-035 |
| Year of manufacture: | 1968 |
| Total airframe hrs: | 4362 hours |
| Engine model: | P&W JFTD12A-4A |
| Fatalities: | Fatalities: 1 / Occupants: 2 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | 16 mls NNE of Ketchikan, AK -
 United States of America
|
| Phase: | Manoeuvring (airshow, firefighting, ag.ops.) |
| Nature: | External load operation |
| Departure airport: | Shelter Cove, AK |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
On July 13, 1996, about 1325 Alaska daylight time, a Sikorsky CH-54A helicopter, N541SB, crashed during aero logging operations, about 16 miles north-northeast of Ketchikan, Alaska. The helicopter was being operated as a visual flight rules (VFR) local area flight under Title 14 CFR Part 133 when the accident occurred. The helicopter, registered to and operated by Silver Bay Logging Company, Juneau, Alaska, was destroyed. The certificated commercial pilot received serious injuries. The copilot, holder of a commercial helicopter certificate, received fatal injuries. Visual meteorological conditions prevailed. The flight originated at a nearby logging camp about 1308.
The pilot & copilot were on an external load, aero logging operation in a military surplus helicopter, lifting an estimated load of 18,000 lbs. Ground personnel heard a popping sound, then saw the tailrotor begin to slow down as the helicopter began to yaw/spin. It descended to sloping terrain in an area of cut logs. Postcrash exam of the tailrotor drive shaft revealed a separation at the number 5 bearing position. The shaft separation exhibited evidence of high heat & melting of adjoining shaft surfaces. The bearing & its housing were not recovered. The bearing had accrued 505 hrs of service, & was 1 of 2 bearing model numbers that were in use. The bearing was manufactured in 1991, & was purchased by the operator from surplus military supplies. The supplier (of the bearing to the operator) had performed an exterior exam of the bearing & marked 'relubed 10/95' on the bearing box. Exam of the remaining tailrotor drive shaft bearings revealed evidence of low grease fill, water & glycol contamination, & wear patterns consistent with misalignment. In civilian service, the bearing was an 'on condition' part. The operator established a service life of 1,000 hours for aero logging operations. A shelf life for the bearing was not established. The manufacturer indicated the bearing should support a 5 year shelf life. Other operators of the accident helicopter in aero logging reported similar examples of low grease fill & bearing contamination from water in both available models of bearing.
Probable Cause: Failure of the number 5 tailrotor bearing. A factor relating to the accident was: the uneven/steep sloping terrain, where the pilot was forced to land. Possible factors were: inadequate handling/labeling of the 'relubed' bearing by intermediate supplyier(s), and/or insufficient shelf life/service limits for military surplus parts.
Accident investigation:
 |
|
Sources:
1. http://www3.ntsb.gov/aviationquery/brief.aspx?ev_id=20001208X06129&key=1
Ex CH-54A Tarhe 68-18433 US Army
Images:
Photo: NTSB
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Oct-2008 10:30 | ASN archive | Added |
| 24-Dec-2009 12:20 | TB | Updated [Cn, Operator, Other fatalities, Location, Source] |
| 26-Dec-2009 07:33 | TB | Updated [Aircraft type] |
| 19-Mar-2011 09:36 | TB | Updated [Time, Location, Source] |
| 21-Dec-2016 19:23 | ASN Update Bot | Updated [Time, Damage, Category, Investigating agency] |
| 18-Oct-2022 18:36 | Captain Adam | Updated [Operator, Narrative, Accident report, Photo] |
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