SEA04LA019 · Kaman K-600
Kaman K-600 · Accident: airframe, component or system failure while maneuvering
From Priest Lake, ID to an unrecorded destination
Event
- NTSB case
- SEA04LA019
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 1 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Kaman K-600
- Aircraft type
- Kaman K-600
- Category
- Helicopter
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N286M
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Priest Lake, IDTo not recorded
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 133: Rotorcraft Ext. Load
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Maneuvering · hover out of ground effect
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Airframe, component or system failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Rotor drive system, main rotor mast(drive shaft) › Fatigue
- Rotor drive system, main rotor mast(drive shaft) › Fractured
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
While ascending in a hover to take the slack out of a long-line, the Part 137 logging helicopter experienced the complete failure of its right main rotor mast (shaft). An NTSB metallurgical inspection determined that the mast had failed due to the propagation of a fatigue crack that originated on the inside surface of an opening in the shaft wall (L-crank slot). The fatigue crack originated in two shallow corrosion pits (0.0033 and 0.0029 of an inch wide) on the inner surface of the L-crank slot. Although the shaft had been overhauled/inspected approximately 1,000 hours prior to the accident (1,200 hour interval), the Military Technical Order that regulates the overhaul of this mast does not address a specific inspection for corrosion, nor how to address any corrosion that is detected.
Probable cause
The total failure of the helicopter's right main rotor shaft while in an ascending hover due to the propagation of a fatigue crack that initiated in a corrosion pit on the surface of a slot in the wall of the subject shaft. Factors include accumulation of corrosion on the surface of the shaft.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA04LA019
- Event ID
- 20031212X02029
- Case number
- SEA04LA019
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 2802d9a5603caf5af322426896e4924b2ef16adffd6f9172caabefc69ddb8a29; retrieved 2026-09-20T18:46:59.700Z.