SEA03LA125 · Sikorsky UH-19D
Sikorsky UH-19D · Accident: partial loss of engine power (mechanical failure) while maneuvering
From La Grande/Union County Airport (LGD) to an unrecorded destination
Event
- NTSB case
- SEA03LA125
- 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
- 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
Sikorsky UH-19D
- Aircraft type
- Sikorsky UH-19
- 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
- N37799
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From La Grande/Union County Airport (LGD), La Grande, ORTo 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 137: Agricultural
- 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 · aerial application
- 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
- Partial 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, clutch assembly › Cross/stripped threaded
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
During an aerial application flight, the pilot reported that during a turn he heard and felt three or four "clunking sounds in the airframe." The pilot continued the pedal turn to the left and then straightened out to approach a field. Rotor rpm was deteriorating as he attempted to auto rotate to the field. The pilot stated that he had "no auto-rotating capability" and landed hard in the field. The helicopter bounced once then touched down again coming to rest on its left side. A post-crash fire consumed the wreckage. On site inspection of the wreckage found that the free wheeling side of the clutch assembly and the main drive shaft assembly nut were disconnected. The items were sent to the NTSB materials laboratory for further inspection. The specialist reported that the drive from the main rotor gearbox to the clutch was severed when the bearing support separated from the drive housing. The threads on the bearing support displayed a shearing off of the crown of the forward full form thread. The flanks of the threads to the rear of the sheared thread displayed no indications of contact by the mating thread on the drive housing. Mechanical damage to the threads on the drive housing was limited to the first two rearmost threads. The flanks of the threads forward of the damaged threads displayed no indications of contact by the mating thread on the bearing support. Deformation of the rear ends of the splines forward of the threads and of the two rearmost threads indicate that it was not fully engaged with the drive housing.
Probable cause
The cross threading and separation of the clutch assembly while maneuvering which resulted in a loss of engine power followed by a hard landing. An inadequate maintenance overhaul was a factor.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA03LA125
- Event ID
- 20030714X01097
- Case number
- SEA03LA125
- 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: e5a2950f101113691e6cb6a672ae2a681ac7f6c094253d3a80319d41c8a496ed; retrieved 2026-09-22T09:03:36.250Z.