WPR21FA300 · Robinson Helicopter Co R66
Robinson Helicopter Co R66 · Accident: abrupt maneuver en route
From Willows Glenn County Airport (KWLW) to Williams, CA
Event
- NTSB case
- WPR21FA300
- 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
- 4 · 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
Robinson Helicopter Co R66
- Aircraft type
- Robinson R66
- 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
- N7000J
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Willows Glenn County Airport (KWLW), Willows, CATo Williams, CA
- Aircraft age
- About 8 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 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
- En route · cruise
- 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
- Abrupt maneuver
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Aircraft › Aircraft oper/perf/capability
- Aircraft › Aircraft propeller/rotor
- 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 was conducting a personal flight during daytime visual flight rules conditions with three passengers aboard. A witness who was driving on a nearby highway observed the helicopter flying on an easterly heading about 50 to 100 ft above ground level. The witness stated that the helicopter was initially straight and level but had suddenly made a sharp left turn. The witness briefly lost sight of the helicopter due to trees; when he reestablished visual contact, he observed the helicopter descend and impact terrain.
Postaccident examination of the helicopter revealed no evidence of any pre-existing mechanical malfunction that would have precluded normal operation. The forward left and right control tube attachment bolts at the nonrotating swashplate were not located at the accident site or within the recovered wreckage. The flight control bolts most likely separated during the accident sequence as a result of an overstress fracture. No evidence of preexisting loosening of the attachment nuts, such as substantial thread imprints in the lug bores, was observed. This damage was consistent with the blade grips contacting the mast, commonly referred to as mast bumping, which occurs due to excessive flapping motion of rotor blades (specifically, up-and-down motion of the blade tips). It is likely that, during the flight, the pilot made an abrupt flight control input that resulted in a main rotor blade contacting the tailboom and a subsequent in-flight breakup. The reason for the pilot’s abrupt control inputs could not be determined.
Probable cause
The pilot’s abrupt flight control input that led to mast bumping and a subsequent in-flight breakup.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR21FA300
- Event ID
- 20210801103602
- Case number
- WPR21FA300
- 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, coordinates, 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: 7b8ed009d85760477db6198b2de93f6e19a38567f08c2c24e9aa1f2e51ff3d0d; retrieved 2026-09-15T07:32:40.697Z.