History of Flight
On June 11, 2014, about 1430 central daylight time, a Bell 206 L4 helicopter, registration N207MY, operated by Westwind Helicopters, Inc., as an on-demand air taxi under 14 CFR Part 135, impacted the waters of the Gulf of Mexico. The commercial pilot and one passenger were fatally injured; the helicopter was destroyed. Visual meteorological conditions prevailed, and company flight following was active. The flight departed Ship Shoal 266B oil platform at 1409, en route to South Timbalier 317 (ST 317) platform.
A witness on ST 317 reported hearing the helicopter approach straight in. The helicopter then began to spin clockwise. The witness heard a snap, saw the baggage compartment door open, and debris exiting the compartment during the spin. After 8–10 rotations, the helicopter went silent and dropped into the water.
The helicopter sank and was recovered from approximately 380 feet of water. The tail boom had separated from the fuselage and was recovered from the surface. One main rotor blade separated about four feet from the mast and was not recovered. Several sections, including the landing skids, cabin door, and floor, were not recovered.
Personnel Information
The pilot held a U.S. commercial pilot certificate with a rotorcraft-helicopter rating and a second-class medical certificate issued November 13, 2013, with the restriction "must wear corrective lenses." At the time of the exam, he reported 13,500 total flight hours, with 260 hours in the previous six months. He also held a Canadian private pilot certificate with ratings for airplane single-engine land, multi-engine land, and helicopter.
Aircraft Information
The Bell 206 L4 is a two-bladed, single-engine helicopter powered by a Rolls-Royce (Allison) 250-C30P turboshaft engine. The last 100-hour inspection was on May 18, 2014, at an aircraft total time of 6,387 hours; the engine had 19,736 hours total. A maintenance discrepancy four days before the accident read "no fwd cyclic." The pilot who entered it reported no forward and limited left cyclic, stating it felt like a jam rather than a hydraulic problem. Maintenance personnel checked the controls and flight-checked the helicopter with no defects noted.
Meteorological Information
At 1450, an automated station at Houma-Terrebonne Airport, about 92 miles north, recorded wind 360° at 4 knots, 6 miles visibility in haze, scattered clouds at 5,000 feet, temperature 93°F, dew point 70°F, barometric pressure 29.91 inHg. Nearby oil platform stations reported various conditions: at 1420, Green Canyon 338 (26 miles south-southwest) reported wind variable at 5 knots gusting to 13 knots, visibility 10 statute miles, sky clear below 12,000 feet. At 1435, Mississippi Canyon (48 miles south-southwest) reported wind 280° at 7 knots, visibility 10 miles, clear skies. No convective SIGMETs were issued for the area. The closest TAF for Houma indicated west-southwest wind at 7 knots, unrestricted visibility, few clouds at 5,000 feet. Winds aloft at 3,000 feet were forecast from 250° at 11 knots. A NAM model sounding for the accident site at 1300 CDT showed surface temperature 28°C, dew point 23°C, relative humidity 75%, density altitude 1,835 feet, surface wind 240° at 7 knots, with no low-level wind shear indicated.
Communications and Radar Information
The helicopter was equipped with a Sky Connect system. On June 11, the system recorded 6 hours 26 minutes of flight, including the departure and en route portion to ST 317. Position data showed the helicopter on an east-southeast heading, altitude generally above 550 feet agl, airspeed about 115 knots. The last recorded position was at 1923:49 GMT, on a heading of 121°, altitude 551 feet, airspeed 111 knots, approximately 0.9 miles from ST 317.
Airport Information
South Timbalier 317 is an oil platform in the Gulf of Mexico, about 67 miles off the coast of Louisiana and 100 miles south of Houma, Louisiana.
Wreckage and Impact Information
The wreckage was transported to the operator's facility near Santa Fe, Texas. Examination by NTSB, FAA, and manufacturer representatives revealed heavy damage: the cabin was destroyed, the cabin floor not recovered; one main rotor blade remained attached to the mast, the other separated about four feet from the mast; the tail boom separated just aft of the fuselage; the tail rotor drive shaft showed rotational scoring near the hangar bearings; the tail rotor gearbox remained with the boom, and both tail rotor blades were attached but bent toward the boom. Flight control connections were secure, but tail rotor controls could not be moved due to damage. Transmission continuity and rotation were established; engine continuity to the accessory was found, and the turbine and compressor sections were free to rotate.
Medical and Pathological Information
An autopsy at the Jefferson Parish Forensic Center determined the cause of death as "multiple blunt force injuries." FAA toxicological testing was not conducted because specimens were ruined during shipment. The pilot's FAA medical records showed no reported chronic medical problems or medications, but the autopsy revealed a large area of myocardial scarring and fibrosis and a patent stent in the left anterior descending coronary artery; other coronary arteries were too damaged to assess. The Jefferson Parish coroner's toxicology test was positive for 2,500 ng/mL of Tramadol, a prescription pain medication.
Test and Research
Components—including the hydraulic system, a section of the main rotor blade, the tail boom, and two sections of the tail rotor drive shaft—were sent to Bell's Field Investigations Laboratory. Fractures on the tail rotor drive section were consistent with overload from extreme bending. The tail boom had buckling damage on the left side, no paint transfer from impacts, and paint cracks consistent with metal buckling. The main rotor blade spar was bent aft and downward, consistent with overload failure. The hydraulic system was removed; filters were partially restricted with fine particles, but the system functionally performed with no anomalies when tested. The three actuators were sent to Woodward HRT for examination and showed no abnormalities or signs of previous malfunction.
Additional Information
Excerpts from the FAA Helicopter Handbook (FAA-H-8083-21A, Chapter 11) describe Loss of Tail Rotor Effectiveness (LTE) as an uncommanded rapid yaw toward the advancing blade, caused by aerodynamic interaction rather than mechanical failure. The handbook lists contributing factors and situations to avoid, such as low and slow flight outside ground effect, specific wind directions, tailwinds altering translational lift, low-speed downwind turns, large power changes at low airspeeds, and flight near obstructions.