SEA96LA219 · Kaman HH-43 B/F
Skyline Helicopters Kaman HH-43 B/F · Accident: airframe, component or system failure en route
From MT to an unrecorded destination
Event
- NTSB case
- SEA96LA219
- 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
- 0 · all aircraft and ground
- Ground fatalities
- 0
- 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 HH-43 B/F
- Aircraft type
- Kaman HH-43
- 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
- N4069R
- Operator
- Skyline Helicopters
- Onboard fatalities
- Unknown
- Route
- From MTTo 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 91: General Aviation
- 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
- En route · cruise
- 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, freewheeling sprag unit › Failure
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot reported that while in cruise flight, the internal autorotation cockpit gauge needles split, and the helicopter lost altitude. The rotor rpm was decreasing, and the pilot initiated an autorotation. During the descent, the pilot noted that the N1 gauge indicated that the engine was running, but there was no power to the rotor. The helicopter landed hard, which drove the landing gear through the belly and separated the tail boom. A postaccident investigation revealed that bearings in the one-way freewheeling sprag clutch had failed. The one-way clutch was not a time-retireable item, and determining total time of the assembly from the maintenance records was not possible.
Probable cause
failure of the freewheeling sprag unit bearings for undetermined reasons.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA96LA219
- Event ID
- 20001208X06818
- Case number
- SEA96LA219
- 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. 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: 305b3295c52a508bb3f1d875828c452cf7db637b1c8e7190f84846fcb0fefc94; retrieved 2026-09-21T21:34:58.937Z.