SEA06LA162 · Kaman HH-43F
Horizon Helicopters Kaman HH-43F · Accident: total loss of engine power (mechanical failure) while maneuvering
From Metaline Falls, WA to Metaline Falls, WA
Event
- NTSB case
- SEA06LA162
- 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 HH-43F
- 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
- N559D
- Operator
- Horizon Helicopters
- Onboard fatalities
- Unknown
- Route
- From Metaline Falls, WATo Metaline Falls, WA
- 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
- Total loss of engine power (mechanical failure)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Rotor drive system, engine to transmission drive › Failure
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
The pilot was about to release a load of logs onto a log pile from an altitude between 150 to 200 feet when ground crewmen heard an explosion, then observed the helicopter descend in a nose down attitude before impacting the log deck. An examination of the accident site by an FAA inspector revealed that all major portions of the helicopter were accounted for. A subsequent examination of the wreckage revealed a failure of the transmission's left-hand cross-shaft internal spline, which resulted in the loss of gearbox timing and subsequent in-flight blade contact and separation. Maintenance records revealed that the helicopter's transmission was overhauled on May 1, 2006; the time between the overhaul and the accident was 409.4 hours. An examination of the fractured transmission center housing was caused by two fatigue cracks, which were probably caused by severe cyclic stresses that resulted from repeated loading and unloading of logs.
Probable cause
The failure of the left-hand cross-shaft input internal spline while the helicopter was in a hover, which resulted in the loss of gear box timing, in-flight blade contact and separation, and the subsequent loss of control and impact with a log deck.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA06LA162
- Event ID
- 20060824X01238
- Case number
- SEA06LA162
- 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: ef851e678e2f5f5caafe7b57fe345098aae486936fea05ab8ca9ffbfd7b4c145; retrieved 2026-09-20T17:05:17.447Z.