SEA93LA105 · Kaman HH-43F
Woody Contracting Kaman HH-43F · Accident: airframe, component or system failure while maneuvering
Event
- NTSB case
- SEA93LA105
- 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
- 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-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
- N846D
- Operator
- Woody Contracting
- Onboard fatalities
- Unknown
- Route
- From not recordedTo 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
- 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
- Destroyed
Cause areas
- Faa(organization) › Inadequate certification/approval
- Rotor drive system, main gearbox/transmission › Fatigue
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE CONVERTED MILITARY HELICOPTER WAS IN A HOVER LIFTING AN EXTERNAL LOAD OF LOGS WHEN THE MAIN ROTOR PYLONS SEPARATED IN FLIGHT, RESULTING IN AN UNCONTROLLED INVERTED DESCENT INTO THE GROUND. ON-SCENE EXAMINATION REVEALED THAT THE TRANSMISSION ROTOR INPUT GEAR SHAFT, P/N K774515-5F, HAD FRACTURED. SAFETY BOARD METALLURGICAL EXAMINATION SHOWED THAT THE FRACTURE WAS CHARACTERISTIC OF FATIGUE FAILURE, AND INDICATED REPETITIVE HIGH LOADS. THE FAA TYPE-CERTIFICATE, BASED ON MILITARY CONFIGURATION, LISTS THE APPROVED ENGINE AS 1100 SHP, AND THE EXTERNAL LOAD LIMIT AS 2,300 LBS. THE FAA HAD APPROVED INSTALLATION OF A 1400 SHP ENGINE, AND OPERATIONS WITH AN INCREASED EXTERNAL LOAD LIMIT OF 4,000 LBS.
Probable cause
FATIGUE FAILURE OF THE ROTOR TRANSMISSION DRIVE SYSTEM, RESULTING FROM THE IMPROPER CERTIFICATION/APPROVAL OF THE AIRCRAFT MODIFICATION BY THE FEDERAL AVIATION ADMINISTRATION.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA93LA105
- Event ID
- 20001211X12472
- Case number
- SEA93LA105
- 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: 3c0a26991ce4bcb6c388eb6dc44440622ca024c521e22b3e99fc942081f15718; retrieved 2026-09-21T00:33:55.144Z.