WPR20LA247 · Bell OH58A
A Farmer Service Bell OH58A · Accident: loss of engine power (total) while maneuvering
From Imperial County Airport (IPL) to Imperial County Airport (IPL)
Event
- NTSB case
- WPR20LA247
- 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
Bell OH58A
- Aircraft type
- Bell OH58
- 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
- N901XV
- Operator
- A Farmer Service
- Onboard fatalities
- Unknown
- Route
- From Imperial County Airport (IPL), Imperial, CATo Imperial County Airport (IPL), Imperial, CA
- 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 · 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
- Substantial
Cause areas
- Aircraft › Aircraft power plant
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot was performing agricultural operations in the helicopter. He made a normal takeoff and completed three passes over the field being sprayed. As he approached wires, the pilot maneuvered the helicopter into a climb and prepared to make a fourth pass. As he was completing a left turn back to the field, the engine experienced a total loss of power. He performed an autorotation, and during the touchdown, the helicopter collided with haystacks.
Postaccident examination of the engine revealed extensive damage to the aft end of the compressor, the spur adapter gearshaft, and the compressor splined adapter. A material analysis revealed that the compressor splined adapter had failed in fatigue. The failure decoupled the turbine section from the compressor section resulting in the loss of engine power.
The compressor splined adapter failed due to a misalignment of the engine's centerline shafting components that resulted from two separate improper maintenance actions. The first improper maintenance action was the installation of an incorrect number of shims at the interface between the rear compressor diffuser and the accessory gearbox.
The second improper maintenance action was the installation of an incorrect compressor splined adapter; the impeller had been machined to fit a larger diameter (-3) compressor splined adapter: however, a smaller diameter (-1) adapter was installed.
Probable cause
The total loss of engine power due to the decoupling of the engine's turbine and compressor sections, which resulted from improper maintenance.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR20LA247
- Event ID
- 20200731X20050
- Case number
- WPR20LA247
- 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: local date, investigation status, cause areas. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2020-07-31.
- API snapshot SHA-256: e6bc1dc303ef721edfbeb13440e92c6fcbee651dcec237d3a2bcc3db4215a1e4; retrieved 2026-09-16T12:19:29.533Z.