WPR18LA140 · Bell OH 58C
Bell OH 58C · Accident: loss of engine power (partial) while maneuvering
From PRIV · Somerton, AZ to PRIV · Somerton, AZ
Event
- NTSB case
- WPR18LA140
- 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 OH 58C
- Aircraft type
- Bell OH-58
- 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
- N82857
- Operator
- Tri Rotor Spray & Chemical
- Onboard fatalities
- Unknown
- Route
- From PRIV · Somerton, AZTo PRIV · Somerton, AZ
- Aircraft age
- About 48 years (built 1970)
- 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 (partial)
- 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
- Personnel issues › Task performance
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 helicopter was performing an aerial application flight in dark night conditions when he felt a vibration. The pilot pulled back on the cyclic control to stop the helicopter's forward movement and maintained this position for the remainder of the flight. Seconds later, the helicopter had descended to 40 ft above ground level (agl), and the low rotor rpm light indication illuminated, accompanied by multiple other warning lights. The helicopter continued to descend and impacted terrain upright. The main rotor blades severed the tail boom, the left skid dug into the ground, and the helicopter rolled over and came to rest on its right side. Examination of the helicopter revealed no anomalies with the flight control system. The engine inspection revealed thermal damage to the combustion liner and 1st stage gas turbine producer vanes, consistent with an irregular spray pattern from the fuel nozzle due to carbon buildup. Although the helicopter's weight at the time of the accident exceeded its published maximum gross weight by 100 lbs, whether this contributed to the helicopter's inability to maintain altitude following the loss of engine power was not determined. The engine logbook indicated that the fuel nozzles were inspected in accordance with the manufacturer's 100-hour inspection checklist about two years before the accident. Although a 100-hour inspection was completed about 4 months before the accident, the maintenance log entry did not specify the work completed, and whether the fuel nozzles were inspected at this time could not be determined; however, the carbon buildup on the fuel nozzles suggested long-term accumulation, and it is likely that maintenance personnel either omitted this inspection item or did not adequately inspect the fuel nozzles. Given the carbon accumulation of the fuel nozzle and signatures of irregular fuel spray, it is likely that the helicopter experienced a partial loss of engine power, which resulted in the subsequent descent into terrain.
Probable cause
A partial loss of engine power during an aerial application flight due to thermal damage to the 1st stage gas producer turbine nozzle and an irregular fuel spray pattern due to carbon buildup of the fuel nozzle. Contributing to the accident was maintenance personnel's inadequate inspection of the fuel nozzle.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR18LA140
- Event ID
- 20180512X11203
- Case number
- WPR18LA140
- 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, coordinates. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2018-05-12.
- API snapshot SHA-256: ecb84f0b9ea73c9b7b774cd6df4a09c38363b54e1fe003156dc4825f855ec9e6; retrieved 2026-09-16T07:09:40.733Z.