# NTSB FTW95LA303: Bell 206B, N57536, West Cameron, July 17, 1995 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: July 17, 1995, 10:35 local (15:35 UTC) - Place: West Cameron - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report November 30, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 19503 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW95LA303 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/19503/pdf - Page: https://openairdocs.org/ntsb/FTW95LA303 ## Probable cause THE DISCONNECT OF THE TAIL ROTOR DRIVE SYSTEM FOR UNDETERMINED REASONS. FACTORS WERE THE PILOT'S INABILITY TO MAINTAIN DIRECTIONAL CONTROL, AND THE LACK OF SUITABLE TERRAIN FOR THE FORCED LANDING. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Rotor failure/malfunction, cruise - rotor drive system,tail rotor drive shaft coupling - disconnected (cause) - miscellaneous,bolt/nut/fastener/clamp/spring - separation - reason for occurrence undetermined (cause) - Forced landing, emergency descent/landing - autorotation - performed, pilot in command - Roll over, landing - flare/touchdown - directional control - not possible, pilot in command (contributing factor) - terrain condition - none suitable (contributing factor) - terrain condition - water ## Analysis WHILE IN LEVEL FLIGHT AT AN ALTITUDE OF 500 TO 700 FEET THE PILOT FELT A HIGH FREQUENCY VIBRATION IN THE TAIL ROTOR ANTI TORQUE PEDALS. SUBSEQUENTLY, A LOW PITCH 'HUM' AND A 'SHUDDERING VIBRATION' WAS FELT, 'FOLLOWED BY A LOUD BANG FROM THE REAR OF THE AIRCRAFT.' THE AIRCRAFT BEGAN TO 'ROTATE TO THE RIGHT', AND THE APPLICATION OF 'FULL LEFT PEDAL' HAD NO EFFECT IN STOPPING THE ROTATION. AFTER 'SEVERAL' 360 DEGREE TURNS, THE PILOT ATTEMPTED UNSUCCESSFULLY TO STREAMLINE THE HELICOPTER. AN AUTOROTATION WAS INITIATED, AND THE AIRCRAFT'S ROTATION WAS REDUCED TO A 'SLOW RIGHT MOTION SPIRAL OR FLAT SPIN.' DURING THE COMPLETION OF THE AUTOROTATION, THE LEFT FLOAT TOUCHED DOWN ON THE WATER FIRST AND THE HELICOPTER ROLLED INVERTED. EXAMINATION OF THE HELICOPTER REVEALED THAT A BOLT HAD SEPARATED FROM THE TAIL ROTOR AFT SHORT SHAFT FORWARD FLEX COUPLING AND THE DRIVE SHAFT WAS FRACTURED. ## Factual narrative On July 17, 1995, at 1035 central daylight time, a Bell Helicopter 206B, N57536, was substantially damaged during a forced landing to the water near West Cameron 575, Gulf of Mexico. The commercial pilot was not injured. The flight was being operated by Air Logistics under Title 14 CFR Part 135 when the accident occurred. The flight originated at West Cameron 575, Gulf of Mexico, and was en route to West Cameron 587B. Visual meteorological conditions prevailed, and a company flight plan was filed. According to the operator and the Pilot/Operator Report, the helicopter was in level flight at an altitude of 500 to 700 feet when the pilot felt a high frequency vibration in the tail rotor anti torque pedals. Subsequently, a low pitch "hum" and a "shuddering vibration" was felt "followed by a loud bang from the rear of the aircraft." The aircraft began to "rotate to the right", and the application of "full left pedal" had no effect in stopping the rotation. After "several" 360 degree turns, the pilot attempted unsuccessfully to streamline the helicopter. An autorotation was initiated, and the aircraft's rotation was reduced to a "slow right motion spiral or flat spin." During the completion of the autorotation, the rate of rotation increased, and as the left float touched down on the water first, the helicopter rolled inverted. Examination of the helicopter by a Federal Aviation Administration inspector following its recovery revealed that a bolt had separated from the tail rotor aft short shaft forward flex coupling, and the drive shaft was fractured. The bolt and nut were not recovered. A hole was torn in the bottom of the engine oil tank. ## Aircraft - Registration: [N57536](https://openairdocs.org/deregistered/N57536-1999-07-13), registration cancelled 1999-07-13, S/N 3124 (OpenAirDocs) - Reported make and model: BELL 206B - Registry model: [Bell 206B](https://openairdocs.org/model/bell-206b) (registry code 1181511) (OpenAirDocs) - Category: Helicopter - Serial number: 3124 - Airframe hours: 9284 - Engines: ALLISON 250-C20B 317 horsepower turbo shaft - Damage: Substantial damage - Flight: Other work use, Part 91 - Operator: Air Logistics - Registered owner: Offshore Logistics - Airworthiness certificate: Standard, Transport - Last inspection: AAIP, July 11, 1995, 20 hours before - Flight plan: Company VFR ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 32; flight instructor, commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--no waivers/lim.; seat: right; flight hours: 6,300 total, 1,000 in this make and model, 6,000 as pilot in command, 130 in the last 90 days, 30 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 15 statute miles - Lowest ceiling: none - Temperature: 95 °F, dew point 75 °F - Altimeter: 29.00 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 19950717049079A](https://openairdocs.org/incident/19950717049079A), Jul 17, 1995: Bell 206B, Gulfofmexico, LA, Substantial damage. (-16) Tail rotor drive shaft failed due to the loss of a bolt and associated hardware that secures the shaft to a drive coupling. The bolt, washers, and nut… 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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.