# NTSB FTW89LA031: MBB BO-105, N2785B, South Marsh 113, December 5, 1988

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: December 5, 1988, 14:06 local (20:06 UTC)
- Place: South Marsh 113
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor, 3 uninjured
- Status: Completed, report January 16, 1990
- Report: Approved by Office Director
- NTSB case key (mKey): 22821
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW89LA031
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/22821/pdf
- Page: https://openairdocs.org/ntsb/FTW89LA031

## Probable cause

FAILURE AND SEPARATION OF ONE OF THE TAIL ROTOR BLADES FOR UNDETERMINED REASONS. THR RESULTING IMBALANCE AND VIBRATION CAUSED THE SEPARATION OF THE 90 DEGREE GEARBOX AND A PORTION OF THE VERTICAL PYLON WHICH NECESSITATED THE EMERGENCY AUTOROTATION TO THE WATER.

## Sequence of events

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

- Airframe/component/system failure/malfunction, climb - to cruise
  - rotor system,tail rotor blade - failure,total (cause)
  - rotor system,tail rotor blade - separation (cause)
  - rotor drive system,tail rotor gearbox(90 deg) - vibration
  - rotor drive system,tail rotor gearbox(90 deg) - separation
- Forced landing, descent - emergency
  - autorotation

## Analysis

AS THE HELICOPTER WAS CLIMBING THRU ABOUT 500 FT, THE PLT HEARD A LOUD NOISE, FELT A SEVERE VIBRATION & SAW DEBRIS FALLING IN FRONT OF THE ACFT. HE BEGAN AN AUTOROTATION & DEPLOYED THE EMERGENCY FLOATS BEFORE LANDING ON WATER IN THE GULF OF MEXICO. THE HELICOPTER REMAINED AFLOAT & THE OCCUPANTS DEPLOYED & ENTERED A RAFT FROM WHICH THEY WERE PICKED UP ABOUT 1 HR LATER. AN INVESTIGATION REVEALED THAT ONE OF THE TAIL ROTOR BLADES HAD SEPARATED & STRUCK A MAIN ROTOR BLADE. THE RESULTING IMBALANCE CAUSED THE GEARBOX TO SEPARATE & FALL IN THE WATER. THE 90 DEG GEARBOX, TAIL ROTOR HUB AND TAIL ROTOR BLADES WERE NOT RECOVERED FROM THE GULF OF MEXICO.

## Aircraft

- Registration: [N2785B](https://openairdocs.org/deregistered/N2785B-1996-01-26), registration cancelled 1996-01-26, S/N S636 (OpenAirDocs)
- Reported make and model: MBB BO-105
- Registry model: [Messerschmitt-Boelkow-Blohm BO-105S](https://openairdocs.org/model/messerschmitt-boelkow-blohm-bo-105s) (registry code 5626006) (OpenAirDocs)
- Category: Helicopter
- Serial number: 636
- Airframe hours: 1751
- Engines: ALLISON 250-C20B 420 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Part 135
- Operator: Air Logistics
- Registered owner: Mdfc Equipment Leasing
- Airworthiness certificate: Standard, Normal
- Last inspection: AAIP, October 28, 1988, 49 hours before
- Departed: SMI7, SOUTH MARSH 7, GM
- Destination: PTN, PATTERSON, LA
- Flight plan: Company VFR

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 46; airline transport, flight instructor; airplane ratings: single-engine land; instrument ratings: airplane, helicopter; medical: valid medical--no waivers/lim.; seat: right; flight hours: 8,826 total, 406 in this make and model, 8,425 as pilot in command, 62 in the last 90 days, 27 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 20° at 7 knots
- Visibility: 7 statute miles
- Lowest ceiling: none
- Temperature: 64 °F, dew point 37 °F
- Altimeter: 30.00 inHg

## Other investigations on N2785B (1)

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.

- [NTSB FTW89FA093](https://openairdocs.org/ntsb/FTW89FA093), May 7, 1989: MBB BO-105S (N2785B), W Cameron Blk, destroyed, 1 fatal. Probable cause: THE PARTIAL ELECTRICAL FAILURE OF THE MICRO-SWITCH FOR THE OUTBOARD LATERAL GUIDE ASSEMBLY, AND THE INCORRECT GUARD INSTALLED ON THE HYDRAULIC TEST SWITCH, RESULTING IN A TOTAL HYDRAULIC FAILURE.…

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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