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| Date: | Friday 10 May 1974 |
| Time: | |
| Type: |  Sikorsky S-61N |
| Owner/operator: | KLM Noordzee Helicopters |
| Registration: | PH-NZC |
| MSN: | 61465 |
| Year of manufacture: | 1969 |
| Fatalities: | Fatalities: 6 / Occupants: 6 |
| Other fatalities: | 0 |
| Aircraft damage: | Destroyed |
| Category: | Accident |
| Location: | North Sea NE of Friesland -
 Netherlands
|
| Phase: | En route |
| Nature: | Offshore |
| Departure airport: | Amsterdam/Schiphol |
| Chaparral oil rig via Texel | |
| Investigating agency: | RvdL |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
During flight outbound to the oil rig "Chaparral" in the Dutch sector of the North Sea, one of the rotor blades failed halfway along its spar due to fatigue originating at a corrosion pit. The failed blade caused rotor disc imbalance, causing the helicopter to encounter excessive vibrations. These vibrations are likely to have caused an on-board fire. The helicopter became uncontrollable and crashed in the North Sea.
Twelve prior spar cracking cases had occurred. Metallurgical investigation by NLR suggested the OEM's "fatigue design methods were highly unconservative" as actual crack propagation after potential detectability by a pre-flight BIM test was rapid.
Accident investigation:
 |
|
Sources:
http://www.hdekker.info/Nieuwe%20map/1974.htm#10.05.1974
https://books.google.co.uk/books/about/Significance_of_a_Rotor_Blade_Failure_fo.html?id=rhe4HAAACAAJ&redir_esc=y
http://www.sciencedirect.com/science/article/pii/S1350630712002725
Location
Images:
Carson Helicopters, Perkasie Heliport, PA
Media:
…their boneyard, a valuable source of repurposed parts, contain relics with stories. Way too many to list. But here are two. The remains of Sikorsky S-61N PH-NZC- flying to a North Sea oil rig, one rotor blade failed due to corrosion. All 6 crew lost May 1974. 3/5 pic.twitter.com/f3ehAQqti4
— GEOAvia (@bclemens) August 14, 2023
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 21-Jan-2008 10:00 | ASN archive | Added |
| 19-Dec-2009 08:56 | TB | Updated |
| 26-Apr-2011 15:54 | TB | Updated [Time, Phase, Nature, Departure airport, Destination airport, Source, Narrative, ] |
| 26-Apr-2011 16:01 | TB | Updated [Destination airport, Narrative, ] |
| 09-Aug-2014 18:36 | Aerossurance | Updated [Nature, Destination airport, Source, Narrative, ] |
| 15-Oct-2015 17:42 | jevage | Updated [Narrative, ] |
| 09-Apr-2016 13:56 | tipekusair | Updated [Photo, ] |
| 11-Aug-2017 11:46 | Aerossurance | Updated [Source, Narrative, ] |
| 19-Jun-2022 04:36 | Ron Averes | Updated [Location, ] |
| 14-Aug-2023 09:44 | Aerossurance | Updated |
| 27-Sep-2025 08:22 | ASN | Updated [Source, Embed code, Category, Accident report, ] |
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