WPR18LA242 · Bell 212
Bell 212 · Accident: flight control system malfunction/failure on approach
From Bald Mountain Helibase, CA to Donnell Fire, CA
Event
- NTSB case
- WPR18LA242
- 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
- Government
- 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 212
- Aircraft type
- Bell 212
- 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
- N512TA
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Bald Mountain Helibase, CATo Donnell Fire, CA
- Aircraft age
- About 41 years (built 1977)
- 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
- Public Aircraft
- 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
- Approach
- 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
- Flight control system malfunction/failure
- 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 propeller/rotor
- Aircraft › Aircraft systems
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot was conducting water bucket operations when he heard a one-per-revolution whispering sound emanating from the helicopter. He elected to return to the helibase and accepted the Air Attack controller’s offer to escort him back. While en route to the helibase, at an airspeed about 60 knots, the whispering sound evolved into a vibration that progressively worsened. The pilot then elected to land as soon as possible at a nearby location. Upon arrival to the precautionary landing site, the vibration momentarily stopped and was followed by a loud bang, an aggressive vertical vibration, and a loss of control. The helicopter impacted steep mountainous terrain and rolled once onto its left side. The occupants of the escort helicopter observed the accident helicopter nose over about 20° to 30°, followed by a 360° flat turn before it impacted the terrain. Examination of the wreckage revealed that multiple components of the main rotor control system had failed along with a span-wise failure of one of the main rotor blades. The drive link associated with the failed rotor blade had failed in overload at its lower lug and swashplate trunnion bearing. The outer race of the trunnion bearing exhibited brinelling consistent with axial movement of the inner section of the bearing. The inner section of the trunnion bearing separated from the rotating swashplate along with the lower lug of the drive link. Gouges and impact marks found on the arms of the non-rotating swashplate were likely made from the lower lug of the drive link as the inner section of the trunnion bearing began to pull out of the outer race. Contact of the lower lug with one of the arms of the non-rotating swashplate likely resulted in the overload failure of the drive link. These liberated components were not recovered. The in-flight failure of the swashplate drive link resulted in the loss of control of the associated main rotor blade. The uncontrolled blade, free to move out of track with the other controlled blade, resulted in at least a partial loss of control of the main rotor system. The associated vibrations from the out-of-track rotors likely resulted in the failure of the swashplate support and the total loss of control of the helicopter.
Probable cause
An in-flight failure of the trunnion bearing and subsequent failure of the drive link and swashplate support, which resulted in the loss of helicopter control.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR18LA242
- Event ID
- 20180827X83714
- Case number
- WPR18LA242
- 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: fc2f4016fff353f96c3e0506d0d72b0cd017f3f1813c0f0bd256afc115f88bf1; retrieved 2026-09-16T08:10:05.393Z.