SEA02LA161 · Air Tractor AT-502B
Air Tractor AT-502B · Accident: total loss of engine power (mechanical failure) during initial climb
From Rigby Airport (U56) to an unrecorded destination
Event
- NTSB case
- SEA02LA161
- 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
Air Tractor AT-502B
- Aircraft type
- Air Tractor AT-502
- 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
- N6146G
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Rigby Airport (U56), Rigby, IDTo 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
- Initial climb
- 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
- Substantial
Cause areas
- Turbine assembly, turbine blade › Separation
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 of the Air Tractor AT-502B had reported observing no abnormalities during engine start and the subsequent application of power during takeoff. Climbing through 100 feet he heard a loud "bang," observed sparks and flames exiting the engine exhaust ports and transitioned to a power off forced landing. As the aircraft was rolling out it encountered a ditch and the main landing gear separated. Post-crash examination of the engine revealed extensive damage to the blades of the compressor turbine disk and erosive burning damage to the vanes of the vane ring situated immediately upstream of the compressor turbine disk. The 22 year old Pratt & Whitney PT6A-34 turboshaft engine had a total of 7,070 hours since new and had undergone an undocumented overhaul 5,820 hours previously to the accident. The last hot section inspection referenced in the engine log occurred 2,871 hours previous to the accident and the last logged inspection was a 100-hour inspection 324 hours and eight months previous to the accident.
Probable cause
The failure of one or more compressor turbine blades resulting in a shutdown of the engine during initial climb resulting in a forced landing. Contributing factors were the eroded condition of the compressor turbine guide vane nozzles and the ditch which the aircraft encountered during the landing rollout.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA02LA161
- Event ID
- 20020904X01517
- Case number
- SEA02LA161
- 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: dd821fbee5b58df144ad72932f85d0c6d52a63b14b02cb2bb71abeaa15d62e89; retrieved 2026-09-21T19:38:02.157Z.