# NTSB LAX92LA175: Hughes 369C, N8311F, Pacific Ocean (Pacific Ocean), April 10, 1992

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: April 9, 1992, 17:00 local (Apr 10, 1992, 00:00 UTC)
- Place: Pacific Ocean (Pacific Ocean)
- Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 2 minor
- Status: Completed, report May 26, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 27597
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX92LA175
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/27597/pdf
- Page: https://openairdocs.org/ntsb/LAX92LA175

## Probable cause

AN UNDETERMINED FAILURE IN THE ROTOR SYSTEM.

## Sequence of events

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

- Airframe/component/system failure/malfunction, landing - flare/touchdown
  - rotor system - undetermined (cause)
  - rotor system - separation

## Analysis

THE HELICOPTER WAS COMPLETING AN AERIAL OBSERVATION FLIGHT (FISH SPOTTING) OVER THE PACIFIC OCEAN NEAR THE ISLAND OF CANTON AND WAS LANDING ON THE SHIP'S HELIPAD.  WHEN THE SKIDS TOUCHED DOWN, THE ROTOR MAST ASSEMBLY SEPARATED FROM THE ROTOR MAST BASE CAUSING THE HELICOPTER TO TURN TO THE LEFT 90 DEGREES.  THE ROTOR MAST ASSEMBLY AND ALL ITS COMPONENTS FELL INTO THE OCEAN AND WERE NOT RECOVERED.  THE HELICOPTER SUSTAINED SUBSTANTIAL DAMAGE.  THE PILOT REPORTED THAT THE HELICOPTER DID NOT EXPERIENCE ANY ABNORMAL CYCLIC MOVEMENTS OR ANY UNUSUAL VIBRATIONS BEFORE THE OCCURRENCE.  THE HELICOPTER HAD ACCRUED 328.5 HOURS SINCE THE LAST ANNUAL INSPECTION.  A 300-HOUR AND A 100-HOUR INSPECTION HAD RECENTLY BEEN COMPLETED.  METALLURGICAL EXAMINATION OF THE ROTOR MAST BASE FRACTURE SURFACES REVEALED OVERLOAD CHARACTERISTICS WITH SOME POST FRACTURE MECHANICAL SMEARING AND DAMAGE.  NO EVIDENCE OF ANY CORROSION OR FATIGUE WAS FOUND.  THE HARDNESS MEASUREMENTS COMPLIED WITH THE MATERIAL SPECIFICATIONS.

## Aircraft

- Registration: N8311F (not matched to a registry record)
- Reported make and model: HUGHES 369C
- Category: Helicopter
- Serial number: 460806S
- Airframe hours: 11013
- Engines: ALLISON 250-C20 425 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Aerial observation, Part 91
- Operator: Voyager, Inc
- Registered owner: Voyager, Inc
- Airworthiness certificate: Standard, Normal
- Last inspection: 100 hour, April 1, 1992, 42 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; commercial; medical: class 2, valid medical--no waivers/lim.; seat: left

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 20 statute miles
- Lowest ceiling: none

## 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 19920409010029A](https://openairdocs.org/incident/19920409010029A), Apr 9, 1992: Hughes 369C, Pacific Ocean, HI, Substantial damage. At touchdown on helipad the entire rotor system separated from helicopter with a loud bang. Rotor mast 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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