# NTSB FTW91FA155: Bell 412, N3909F, Garden Banks, August 26, 1991

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Field investigation · Final report
- Date: August 26, 1991, 07:15 local (12:15 UTC)
- Place: Garden Banks
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal, 4 serious, 1 minor, 7 uninjured
- Status: Completed, report September 14, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 23277
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW91FA155
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/23277/pdf
- Page: https://openairdocs.org/ntsb/FTW91FA155

## Probable cause

OVERHEATING AND SUBSEQUENT FAILURE OF THE NUMBER ONE TAIL ROTOR HANGER BEARING FOR AN UNDETERINED REASON, AND FAILURE OF THE TAIL ROTOR DRIVE SHAFT.

## Sequence of events

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

- Airframe/component/system failure/malfunction, approach
  - rotor drive system,tail rotor drive shaft bearing - overtemperature (cause)
  - reason for occurrence undetermined (cause)
  - rotor drive system,tail rotor drive shaft bearing - failure,total (cause)
  - rotor drive system,tail rotor drive shaft - failure,total (cause)
- Loss of control - in flight, approach
  - directional control - not possible
- Forced landing, descent - emergency
  - autorotation - attempted, pilot in command
- Roll over, landing
  - misc rotorcraft,emergency floatation gear - overload

## Analysis

THE HELICOPTER WAS ON FINAL APCH TO AN OIL RIG IN THE GULF OF MEXICO, WHEN TAIL ROTOR AUTHORITY & DRCTNL CTL WERE LOST. AS THE CREW BEGAN AN AUTOROTATION TO THE WATER, THE HELICOPTER SPUN OUT OF CTL TO THE RGT. IT MADE 2 TO 3 REVOLUTIONS & IMPACTED THE WATER. THE RGT FLOATATION GEAR DEPLOYED, BUT THE LEFT FLOATATION GEAR DIDN'T DEPLOY, BECAUSE THE PNEUMATIC LINES WERE PULLED APART DRG IMPACT. SUBSEQUENLTY, THE HELICOPTER ROLLED OVER DRG TOUCHDOWN IN THE WATER. THE CREW & 10 OF 11 PSGRS ESCAPED THRU THE EMERG WINDOWS. THE OTR PSGR REMAINED IN HIS SEAT (INCAPACITATED FM INJURIES) & DROWNED. AN INVESTIGATION REVEALED THE #1 HANGER BEARING HAD OVERHEATED & DISINTEGRATED AT AN EXTREMELY HIGH TEMPERATURE. SUBSEQUENTLY, THE TAIL ROTOR DRIVE SHAFT FAILED.

## Aircraft

- Registration: [N3909F](https://openairdocs.org/deregistered/N3909F-2013-04-08), registration cancelled 2013-04-08, S/N 33015, built 1981 (OpenAirDocs)
- Reported make and model: BELL 412
- Registry model: [Bell 412](https://openairdocs.org/model/bell-412) (registry code 1182202) (OpenAirDocs)
- Registry engine: [Pratt & Whitney Canada PT6T-3](https://openairdocs.org/engine/pratt-whitney-canada-pt6t-3) (registry code 52102, turbo-shaft) (OpenAirDocs)
- Category: Helicopter
- Serial number: 33015
- Airframe hours: 10337
- Engines: P&W PT6T-3B 1600 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Part 135
- Operator: Petroleum Helicopters
- Registered owner: Robert D. Armstong
- Airworthiness certificate: Standard, Transport
- Last inspection: Continuous airworthiness, June 13, 1991, 192 hours before
- Departed: NONE, SHIP SHOLE 248, GM
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 44; airline transport, commercial; instrument ratings: helicopter; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 12,400 total, 2,145 in this make and model, 8,633 as pilot in command, 89 in the last 90 days, 34 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 70° at 3 knots
- Visibility: 10 statute miles
- Lowest ceiling: 5,000 ft broken
- 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 19910826036769A](https://openairdocs.org/incident/19910826036769A), Aug 26, 1991: Bell 412, Gardenbanks Blk, LA, Substantial damage, 1 fatal. Tail rotor drive shaft hanger bearing failed. Spun into water and rolled on landing. Improper bearing cleaning.

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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