WPR24LA070 · Air Tractor Inc AT-502A
Blair Ground Services Air Tractor Inc AT-502A · Accident: loss of engine power (total) during initial climb
From Lemoore, CA (private airstrip) to Sequoia Field (D86)
Event
- NTSB case
- WPR24LA070
- 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 Inc AT-502A
- 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
- N6126U
- Operator
- Blair Ground Services
- Onboard fatalities
- Unknown
- Route
- From Lemoore, CA (private airstrip)To Sequoia Field (D86), Visalia, CA
- Aircraft age
- About 29 years (built 1995)
- 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 91: General Aviation
- 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
- 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
- Substantial
Cause areas
- Aircraft › Aircraft power plant
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot was repositioning an empty agricultural airplane for fertilizer application. During takeoff, the airplane failed to develop full power. At about 200 feet above ground level (agl) the engine rolled back to near idle. The pilot’s attempt to vary the power lever inputs did not affect engine power output, and he initiated a forced landing into a grove of small pistachio trees and soft dirt. Postaccident examination of the engine and follow-up bench testing of the engine compressor bleed-off valve (BOV) revealed an abnormal amount of air leaking around the piston. Disassembly of the BOV revealed a piston ring set was stuck within the piston groove, consistent with an abnormal air leak and irregular function. Abrasive and adhesive wear was observed on the piston rings and piston groove. The wear was likely due to environmental contaminants or twisting in the BOV’s metal piston ring profile. Based on the condition of the BOV’s rings, the BOV likely did not fully close during the accident flight, which resulted in a partial loss engine power during takeoff.
Probable cause
A partial loss of engine power due to the malfunction of the engine compressor bleed-off valve.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR24LA070
- Event ID
- 20240110193638
- Case number
- WPR24LA070
- 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, cause areas. 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: 86aa537ded6d9108612c413759c8f5d0698f14ff5537023873248f17ad8c1181; retrieved 2026-09-16T18:25:45.779Z.