# NTSB LAX92LA349: Hiller UH12-E, Saloy Conver, N9753C, Arvin, CA, August 15, 1992

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: August 15, 1992, 06:15 local (13:15 UTC)
- Place: Arvin, CA
- Coordinates: 35.250354, -118.909187 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=35.2504&lon=-118.9092&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report July 29, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27731
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX92LA349
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27731/pdf
- Page: https://openairdocs.org/ntsb/LAX92LA349

## Probable cause

THE FAILURE OF THE TENSION TORSION BAR PIN DUE TO FATIGUE.  CONTRIBUTING TO THIS ACCIDENT WAS THAT IT WAS NOT POSSIBLE FOR THE PILOT TO FLARE THE HELICOPTER ON LANDING.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, maneuvering - turn to reverse direction
  - rotor system,main rotor blade retaining pin/bolt - fractured (cause)
  - rotor system,main rotor blade retaining pin/bolt - fatigue (cause)
- Forced landing, descent - emergency
  - autorotation - performed, pilot in command
- Hard landing, landing - flare/touchdown
  - flare - not possible, pilot in command (contributing factor)

## Analysis

THE PILOT WAS CONDUCTING AN AERIAL APPLICATION FLIGHT.  WHILE EXECUTING THE PROCEDURE TURNAROUND, THE MAIN ROTOR BLADE TENSION TORSION PIN FAILED DUE TO FATIGUE.  THIS PART HAS A LIFE LIMIT OF 643 HOURS.  THE FAILED PIN ACCRUED 641.5 HOURS.  THE PILOT WAS ABLE TO EXECUTE AN AUTOROTATION, BUT WAS UNABLE TO FLARE WHICH RESULTED IN A HARD LANDING.

## Aircraft

- Registration: [N9753C](https://openairdocs.org/deregistered/N9753C-2013-05-30), registration cancelled 2013-05-30, S/N 2340, built 1965 (OpenAirDocs)
- Reported make and model: HILLER UH12-E, SALOY CONVER (UH12-E, SA)
- Registry model: [Hiller UH-12E](https://openairdocs.org/model/hiller-uh-12e) (registry code 4360122) (OpenAirDocs)
- Registry engine: [Lycoming VO-540 series](https://openairdocs.org/engine/lycoming-vo-540-series) (registry code 41534, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 2340
- Airframe hours: 6352
- Engines: ALLISON 250-C20B 420 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: San Joaquin Helicopters, Inc.
- Registered owner: San Joaquin Helicopters, Inc.
- Airworthiness certificate: Special, Restricted (Special)
- Last inspection: Annual, April 1, 1992, 323 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 38; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: center; flight hours: 7,890 total, 3,502 in this make and model, 7,721 as pilot in command, 238 in the last 90 days, 89 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 35 statute miles
- Lowest ceiling: none
- Temperature: 81 °F, dew point 63 °F
- Altimeter: 29.00 inHg

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19920815031449A](https://openairdocs.org/incident/19920815031449A), Aug 15, 1992: Hiller UH12E, Arvin, CA, Substantial damage. Rotor system failed during spray run. Severe oscillation and vibration prior impact. Rotor blade torsion pin failed

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.

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