# Accident 19980323004139A: Bell 205A1, Los Angeles, CA, March 23, 1998

- Type: FAA accident report (Accident/Incident Data System), as reported
- Date: March 23, 1998, 07:40 local time
- Place: Los Angeles, CA
- Damage: Destroyed
- Phase of flight: Normal Cruise
- Operating rules: General operating rules (Part 91)
- Location: 34.0994° N, 118.3190° W: From the FAA, an estimate near the named town, within about 3 miles
- Nearby events: https://openairdocs.org/map.md?lat=34.0994&lon=-118.3190&mi=10
- Aircraft: N90230, a cancelled registration (https://openairdocs.org/deregistered/N90230-2007-03-12) (OpenAirDocs)
- Registry model: Bell 205A-1 (registry code 1181414, https://openairdocs.org/model/bell-205a-1) (OpenAirDocs)
- Registry engine: Lycoming T-53 series (registry code 41552, https://openairdocs.org/engine/lycoming-t-53-series) (OpenAirDocs)
- Reported make and model: BELL 205A1
- Reported engine: LYC T5313B
- People aboard: 4
- Fatal injuries: 4
- Pilot flight hours: 1,570 total, 219 in this make and model, 21 in the last 90 days
- NTSB investigation: [NTSB LAX98GA127](https://openairdocs.org/ntsb/LAX98GA127) (OpenAirDocs)
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/19980323004139A

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

LOST TAIL ROTOR GEAR BOX AND TAIL ROTOR ENROUTE. CRASH LANDED IN AUTOROTATION. FOUND FATIGUE CRACKING PROBLEM. (.4) 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 FATIQUE 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 DEFORMATIONRESULTING 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 ALLOWD 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.

## The NTSB's investigation of this event (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB LAX98GA127](https://openairdocs.org/ntsb/LAX98GA127), Mar 23, 1998: Bell 205A-1 (N90230), Los Angeles, CA, destroyed, 4 fatal. 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…

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record.

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