WPR23LA313 · Bell OH-58A
Blair Helicopter Service Bell OH-58A · Accident: mast bumping while maneuvering
From Stratford, CA to an unrecorded destination
Event
- NTSB case
- WPR23LA313
- 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-58A
- 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
- N861CC
- Operator
- Blair Helicopter Service
- Onboard fatalities
- Unknown
- Route
- From Stratford, CATo not recorded
- Aircraft age
- About 10 years (built 2013)
- 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
- Mast bumping
- 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 oper/perf/capability
- Aircraft › Aircraft propeller/rotor
- Personnel issues › Action/decision
- Personnel issues › Task performance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot was conducting an aerial application flight and initiated a climbing left turn to return to the field. The helicopter’s low rotor rpm warning light illuminated, and the pilot heard the low rotor audio tone in his headset. The pilot lowered the collective to attempt to regain engine and rotor speed while maneuvering to avoid a drainage culvert. While the pilot was maneuvering, tThe tailboom separated, the right skid contacted the culvert, and the helicopter rolled over onto its right side. T; the helicopter sustained substantial damage to the fuselage and the tail rotor had separated from the tailboom. Examination of the helicopter, including the transmission and hydraulic systems, revealed no preaccident mechanical malfunctions or failures that would have precluded normal operation. The tailboom was completely separated just aft of the horizontal stabilizers, severing the tail rotor and gear box. Witness marks from the main rotor blades were observed on the tail rotor driveshaft cover, aft of the horizontal stabilizers. A test run of the engine revealed no anomalies. The helicopter was loaded about 21 pounds below its maximum gross weight and operated in a high-temperature environment. Performance calculations based on the pilot’s estimates of environmental conditions and the helicopter’s weight revealed 5 minute maximum power availability of about 92% torque. It is likely that while trying to maintain the climbing left turn, which required increased lift due to the increased load factor, the pilot demanded more power than the engine could produce and overpitched the main rotor blades. The resulting low rotor speed led to a reduction of lift and stiffness and lag in the flight control response, which the pilot interpreted as a hydraulics failure. It is likely that while the pilot maneuvered to avoid the culvert, the low rotor speed allowed the main rotor blades to flap down and sever the tailboom. At the same time, the main rotor hub teetered downward and fractured the mast, consistent with mast bumping, which separated the main rotor system from the transmission.
Probable cause
The pilot’s overpitching of the main rotor blades while maneuvering at low altitude in a high-temperature environment at high gross weight, which resulted in a reduction of engine and rotor speed, excessive main rotor blade flapping, mast bumping, and impact with terrain.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR23LA313
- Event ID
- 20230814192867
- Case number
- WPR23LA313
- 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: aebf35cbfa35557dec8b5c3bef20eae20af6f36fccfb6cb2f7890f2a9c01ce66; retrieved 2026-09-16T18:00:05.288Z.