LAX98GA127 · Bell 205A-1
Los Angeles City Fire Dept Bell 205A-1 · Accident: rotor failure/malfunction en route
From Los Angeles, CA to Los Angeles, CA
Narrative check · The NTSB narrative appears to contradict this record's flight rules. Values are shown as recorded, not corrected; compare with the narrative.
Event
- NTSB case
- LAX98GA127
- 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
- 0
- 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 205A-1
- Aircraft type
- Bell 205
- 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
- N90230
- Operator
- Los Angeles City Fire Dept
- Onboard fatalities
- Unknown
- Route
- From Los Angeles, CATo Los Angeles, 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
- Public Aircraft Narrative disagrees
- 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
- First occurrenceThe 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
- Rotor failure/malfunction
- 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
- Rotor system, tail rotor › Bent
- Rotor system, tail rotor › Fatigue
- Rotor system, tail rotor › Separation
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
During an air ambulance flight in the public-use helicopter, the tail rotor and gearbox separated from the helicopter. The pilot autorotated to a forced landing. During the descent over mountainous terrain, the helicopter collided with trees and impacted hard terrain on its left side which crushed inward. The operator's policy required all crewmembers to wear helmets during flight. Helmets were not provided for the two paramedics. During the crash sequence, the passenger seat stanchions and tubing buckled, which resulted in multiple lap belt anchor point separations and the catapulting of crewmembers into the overhead cockpit panel. Safety Board survival factors documentation in conjunction with helmet crashworthiness analysis revealed helicopter impact forces were within human tolerance. The lack of and/or inadequate strength helmets and the lap belt anchor point failures allowed crewmembers' excursions resulting in head trauma. The tail rotor component separations in flight resulted from a fatigue crack originating in the surface of the yoke onto which the tail rotor blades had been attached. In 1996, Bell issued an Alert Service Bulletin (ASB) number 205-96-68, which was designed to measure yoke deformation resulting from adverse in-flight or ground handling operations which imposed excessive bending loads. The test protocol was found problematic in its accuracy due to technical errors in the bulletin and a lack of clarity. City mechanics failed to adhere to all of the ASB's requirements. The bent yoke fractured at a total time in service of approximately 4,113 hours, about 117 hours after its inspection for evidence of deformation. The yoke's stainless steel composition and requisite metallurgical properties were confirmed by the Safety Board. An x-ray diffraction examination of the yoke revealed reduced compressive residual stress in the fracture origin region which allowed operational loads to initiate and propagate the fatigue crack. This significant reduction of the residual stress was likely due to excessive flexure (bending) of the yoke. The initiating event which overstressed and bent the yoke was not identified.
Probable cause
An excessive bending load applied to the tail rotor blade assembly of an undetermined origin which produced a fatigue crack, the separation of the assembly, and a forced landing. Factors were the lack of suitable terrain to perform a forced landing, the manufacturer's unclear maintenance bulletin instruction and procedures which facilitated the operator's inadequate inspection for the yoke's straightness, and the inadequacy of restraint systems and protective equipment.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX98GA127
- Event ID
- 20001211X09703
- Case number
- LAX98GA127
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (5)
- 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. 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: 17622dcb3e040effd353f2203b45814f7f2406074e240ecd39508d2b7e3c0603; retrieved 2026-09-20T22:38:53.528Z.
- Corrected after a review of the NTSB narrative, which states these values explicitly: operation. The narrative states "During an air ambulance flight in the public-use helicopter"; the operator was the Los Angeles City Fire Department, so the flight was a public aircraft operation, not Part 91 general aviation.