ENG20LA046 · Thrush S2R-H80
Custom Ag and Air Thrush S2R-H80 · Incident: loss of engine power (total) while maneuvering
From Donalsonville Municipal Airport (17J) to an unrecorded destination
Event
- NTSB case
- ENG20LA046
- 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
- Incident
- 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
Thrush S2R-H80
- Aircraft type
- Thrush S2
- Category
- Airplane
- 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
- N6216K
- Operator
- Custom Ag and Air
- Onboard fatalities
- Unknown
- Route
- From Donalsonville Municipal Airport (17J), Donalsonville, GATo not recorded
- Aircraft age
- About 4 years (built 2016)
- 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 · low-altitude flying
- Defining eventThe 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
- Loss of engine power (total)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Minor
Cause areas
No findings designated as a cause are recorded in the NTSB data yet.
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
The incident engine suffered a release of low-energy power turbine blade debris due to a power turbine overspeed event. One or more hex nuts that secure the torque meter support within the reduction gearbox came loose and backed off from its threaded stud. A loose nut then became wedged between the mating teeth of the stage 2 planetary gears and crown wheel and the sudden torque shock caused teeth to fracture on one stage 1 planetary gear. Once these teeth fractured, mis-meshing between the stage 1 planetary gears and the sun gear occurred resulting in the 360° fracture and liberation of the sun gear teeth. The reduction gearbox then became decoupled from the power turbine, allowing for overspeed to occur
Probable cause
A total loss of engine power due to a loose torque meter attachment nut in the reduction gearbox that jammed the planetary gearset causing the power turbine shaft to separate from the power turbine disk, resulting in the power turbine overspeeding and shedding blades that penetrated the compressor turbine case.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ENG20LA046
- Event ID
- 20201001102067
- Case number
- ENG20LA046
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
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: 8e30e40b042f2fe66f944cba40a14d1e19df4894de1da74814285414bb94d72c; retrieved 2026-09-16T13:09:17.203Z.