# NTSB LAX86MA309: Aerospatiale AS-355F-1, N57967, Morgan City, LA, July 18, 1986

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Major investigation · Final report
- Date: July 18, 1986, 07:55 local (12:55 UTC)
- Place: Morgan City, LA
- Coordinates: 29.730255, -91.130798 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=29.7303&lon=-91.1308&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report February 12, 1988
- Report: Approved by Office Director
- NTSB case key (mKey): 25285
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX86MA309
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/25285/pdf
- Page: https://openairdocs.org/ntsb/LAX86MA309

## Sequence of events

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

- Airframe/component/system failure/malfunction, approach - vfr pattern - final approach
  - fuselage,attachment - failure,partial
  - reason for occurrence undetermined (cause)
  - fuselage,attachment - fatigue
  - fuselage,attachment - failure,total
- Loss of control - on ground/water, landing - flare/touchdown
  - miscellaneous - vibration

## Analysis

THE PLT FLEW TO A NEARBY ARPT TO PRACTICE TAKEOFFS & LNDGS. HE RPRTD THAT AFTER 3 LNDGS 'OUT OF A HOVER,' HE RETURNED TO THE DEPARTURE HELIPORT & LNDD AGAIN FROM A HOVER. DRG TOUCHDOWN, THE HELICOPTER BGN TO ROCK FM SIDE TO SIDE & ENTEREDGROUND RESONANCE. THE PLT RPRTD HE LOWERED THE COLLECTIVE PITCH TO THE BOTTOM STOP, BUT STATED THE SIDEWARD BOUNCING FM SKID TO SKID WORSENED. HE REACHED FOR THE OVERHEAD THROTTLES, BUT WAS BEING FLAILED ABOUT THE COCKPIT & COULD NOT HOLD ONTO THEM. SUBSEQUENTLY, THE HELICOPTER WAS EXTENSIVELY DAMAGED. WITNESSES VERIFIED THE SIDE TO SIDE BOUNCING & RPRTD HEARING A LOUD METALLIC SOUND BEFORE THE HELICOPTER TOUCHED DOWN. A POST-CRASH EXAM REVEALED THE L FRONT, L REAR & RGT REAR SUPPORT TUBES (GEARBOX BARS) WERE BUCKLED IN A 'D' SHAPE & FRACTURED AT MIDSPAN. METALLURGICAL EXAM OF THE FRACTUREAREAS DISCLOSED EVIDENCE OF HIGH STRESS, LOW AMPLITUDE FATIGUE. NO HISTORY OF HARD LNDGS OR MAINTAINANCE/MANUFACTURING DISCREPANCIES WERE FND CONCERNING THE GEARBOX BARS; L FRONT BAR HAD 1522 HRS OF SVC, REAR BARS HAD 3396 HRS OF SVC.

## Aircraft

- Registration: [N57967](https://openairdocs.org/deregistered/N57967-1988-11-30), registration cancelled 1988-11-30, S/N 5169 (OpenAirDocs)
- Reported make and model: AEROSPATIALE AS-355F-1
- Registry model: [Aerospatiale AS 355F1](https://openairdocs.org/model/aerospatiale-as-355f1) (registry code 8680810) (OpenAirDocs)
- Category: Helicopter
- Serial number: 5169
- Airframe hours: 3397
- Engines: ALLISON 250-C20F 250 horsepower turbo shaft
- Damage: Destroyed
- Flight: Instructional, Part 91
- Operator: Mobil Oil Corp.
- Registered owner: Petrolueum Helicopters Inc
- Airworthiness certificate: Standard, Normal
- Last inspection: Continuous airworthiness, July 11, 1986, 20 hours before
- Airport: Mobil Oil Heliport

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 52; commercial, airline transport, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane, helicopter; medical: class 1, valid medical--no waivers/lim.; seat: right; flight hours: 16,500 total, 15 in this make and model, 16,400 as pilot in command, 320 in the last 90 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 81 °F

## 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 19860718034609A](https://openairdocs.org/incident/19860718034609A), Jul 18, 1986: Aerosp AS355F1, Morgan City, LA, Destroyed. The helicopter disintegrated from ground resonance on landing. 3 gearbox support bars showed fatigue fractures.

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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