# NTSB LAX86MA268: Aerospatiale AS-355F-1, N5796T, Galveston, TX, June 18, 1986

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Major investigation · Final report
- Date: June 18, 1986, 09:55 local (15:55 UTC)
- Place: Galveston, TX
- Coordinates: 29.300592, -94.789642 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=29.3006&lon=-94.7896&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report May 27, 1988
- Report: Approved by Office Director
- NTSB case key (mKey): 25283
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX86MA268
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/25283/pdf
- Page: https://openairdocs.org/ntsb/LAX86MA268

## Sequence of events

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

- Miscellaneous/other, approach
  - fuselage - vibration
  - planned approach - continued
- Airframe/component/system failure/malfunction, landing
  - reason for occurrence undetermined (cause)
  - fuselage,attachment - fatigue
  - rotor system,main rotor hub flapping hinge/stop(s) - failure,total

## Analysis

THE PLT RPRTD THAT WHILE APCHG AN OIL DRILLING PLATFORM FOR A LNDG, HE OBSERVED THE MAIN ROTOR BLADES GO OUT OF TRACK ABOUT 8 TO 10 INCHES. HE ALSO RPRTD THE HELICOPTER DEVELOPED A 1:1 VERTICAL VIBRATION. DRG THE LNDG, THE HELICOPTER ENTERED INTO GROUND RESONANCE & THE PLT IMMEDIATELY SHUT DOWN BOTH ENGINES. AN EXAM OF THE HELICOPTER REVEALED THE LEFT FORWARD TRANSMISSION SUPPORT BAR (TSB) WAS BUCKLED & CRACKED AT MIDSPAN. A METALLURGICAL EXAM OF THE FRACTURE AREA ON THE TSB REVEALED EXTENSIVE, LOW CYCLE, HIGH AMPLITUDE, FATIGUE CRACKING. THERE WAS EVIDENCE THAT THE PROPAGATION TIME OFTHE FATIGUE OCCURRED OVR ABOUT 5 HRS OF OPN. THE INV DID NOT REVEAL WHEN THE ORIGINAL BUCKLING OF THE TSB OCCURRED. NO HISTORY OF A PREV HARD LNDG OR GND REASONANCE WAS FND. ALSO, THE RED ARM OF THE STARFLEX HAD FAILED; AN EXAM INDCD IT HAD RUPTURED EITHER UNDER STATIC LOADS, OR VERY RAPIDLY UNDER HI DYNAMIC LOADS. WHEN TESTED, EXTN & RETRACTION TIMES OF LNDG GEAR DAMPERS WERE 8.34 TO 10.38 SEC; AFTER ACDNT, TIME LMTS ESTABLISHED AT 6 TO 13 SEC, PREVIOUSLY 11.1 TO 13.1 SEC

## Aircraft

- Registration: [N5796T](https://openairdocs.org/deregistered/N5796T-2010-12-07), registration cancelled 2010-12-07, S/N 5166 (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: 5166
- Airframe hours: 3500
- Engines: ALLISON 250-C20F 450 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Positioning, Part 91
- Registered owner: Petroleum Helicopters, Inc.
- Airworthiness certificate: Standard, Normal
- Last inspection: Continuous airworthiness, June 5, 1986, 20 hours before
- Departed: HIGH ISLAND 571, TX
- Airport: High Island 571 Platform

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 40; commercial; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 7,790 total, 33 in this make and model, 7,757 as pilot in command, 87 in the last 90 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 300° at 3 knots
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 82 °F, dew point 70 °F
- Altimeter: 30.00 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 19860618087109A](https://openairdocs.org/incident/19860618087109A), Jun 18, 1986: Aerosp AS355F1, High Island, TX, Substantial damage. The helicopter experienced ground resonance while landing on an oil rig. Transmission support tube fatigue cracked.

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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