ATL96LA129 · Bell 47G-4A (SOLOY) 47G-4A (SO
Bell 47G-4A (SOLOY) 47G-4A (SO · Accident: airframe, component or system failure while maneuvering
From No airport to an unrecorded destination
Event
- NTSB case
- ATL96LA129
- 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
Bell 47G-4A (SOLOY) 47G-4A (SO
- Aircraft type
- Bell 47
- 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
- N23PH
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From No airportTo 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
- Airframe, component or system failure
- Also codedOther events the NTSB coded in the sequence, such as a wire strike after a loss of power. Flight Findings uses them for its kinds of event. Glossary
- Tree(s)
- 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
- Company maintenance personnel › Maintenance, lubrication, not performed
- Rotor drive system, tail rotor drive shaft coupling › Seized
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
During an aerial application operation, the pilot was making east and west swath runs. He reported that he had dispensed about half of his load, when he noted a vibration in the tail rotor pedals during a turn-around maneuver. He conducted three more swath runs with the vibration becoming progressively worse during each turn-around. Subsequently, during the fourth turn-around, the tail rotor drive was lost when the tail rotor drive shaft aft universal joint failed. Examination of the universal joint revealed a lack of lubricant, and the tail rotor drive shaft was discolored blue. There was no log book entry to indicate that the universal joint had been lubricated in the 150 plus hours of operation since the last inspection. The manufacturer's recommended maintenance practices included lubrication of the universal joint after each 50 hours of operation.
Probable cause
failure of the aft universal joint of the tail rotor drive shaft, due to inadequate lubrication by company maintenance personnel. A factor relating to the accident was the pilot's delay in discontinuing the flight after noting a progressively worse tail rotor drive vibration.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ATL96LA129
- Event ID
- 20001208X06680
- Case number
- ATL96LA129
- 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: 44ff73ad50269b396065400b26c11fd1eb8b2c63459993322b60fee014da1176; retrieved 2026-09-21T21:35:19.109Z.