History of Flight
On August 13, 2013, at about 1310 central daylight time, a Bell 407 helicopter, registration N53LP, ditched in the Gulf of Mexico, Louisiana, after losing engine power. The pilot and two passengers received minor injuries. The helicopter sustained substantial fuselage damage. The flight was operated by Panther Helicopters, Inc. under 14 Code of Federal Regulations Part 135 as a passenger flight. Day visual flight rules (VFR) conditions prevailed, and no flight plan was filed. The flight originated from the Ship Shoal (SS) 208H offshore production platform and was destined for SS 209A.
According to the pilot, the day had been routine. He conducted multiple flights between platforms and the Harry P. Williams Memorial Airport (PTN). At SS 208H, the pilot loaded two passengers for the return to PTN. During the takeoff, as the helicopter began to increase airspeed, a loud bang was heard. The helicopter yawed left, the low-rotor horn sounded, and the low-rotor light illuminated. The pilot lowered the collective fully, applied forward cyclic, and activated the float system. The engine out and engine control system warnings activated. Unable to gain airspeed, the pilot leveled the helicopter and applied full collective to cushion the water impact. After the rotor stopped, the pilot instructed passengers to exit. He smelled an electrical fire and turned off the battery, but the battery did not disconnect. The pilot, slightly pinned by the instrument panel, exited through a passenger door. All three occupants stayed with the helicopter until rescued by a crew/supply boat.
Witnesses on the helideck heard a noise resembling a shotgun report and saw the helicopter descend and hit the water. The main rotor blades struck the water, and the blades, transmission, and engine separated from the airframe.
Personnel Information
The pilot, age 30, held a commercial pilot certificate and a certified flight instructor certificate with rotorcraft-helicopter and instrument helicopter ratings. His second-class medical certificate was issued on November 15, 2012, with a corrective lenses limitation. His last Airman Competency/Proficiency Check was on June 12, 2013. He had accrued about 1,136 total flight hours, including 133.8 hours as pilot-in-command in the Bell 407.
Aircraft Information
N53LP was a 1998 Bell 407 helicopter, serial number 53319, powered by a Rolls-Royce 250-C47B turboshaft engine. The engine drove a four-bladed main rotor and a two-bladed tail rotor. The helicopter was configured for one pilot and six passengers. Its maximum gross weight was 5,250 pounds; at the time of the accident, it weighed 4,345 pounds. Maintenance was performed under a manufacturer's continuous inspection program; the last inspection, a 300-hour progressive inspection, was completed on August 8, 2013, at 4,253.6 total hours.
The engine featured a Triumph Engine Control Systems EMC-35R full authority digital electronic control (FADEC) system. The FADEC electronically controls fuel flow via a hydro-mechanical unit (HMU) and electronic control unit (ECU). The ECU monitors engine condition and records exceedances and faults.
Meteorological Information
At 1250, weather at Houma-Terrebonne Airport (63 nautical miles from the accident site) was: wind 210° at 8 knots, visibility 5 statute miles, rain and mist, broken clouds at 3,400 feet, temperature 29°C, dew point 33°C, altimeter 30.04 inches of mercury.
Wreckage and Impact
The tailcone remained attached to the fuselage; the engine and transmission separated. Large components were recovered from the water. The engine was found underwater and retrieved. The transmission was not recovered. A float bag exhibited a puncture.
Tests and Research
Postaccident toxicological tests on the pilot were negative. The engine was examined at Rolls-Royce; bearings showed no thermal distress, but damage consistent with centrifugal compressor rotation on its impeller shroud was observed. Blade rubbing witness marks were present. The gearbox had only salt-water corrosion. No fuel or oil bypass activation.
Data from the ECU confirmed a power loss. Prior to the loss, FADEC operated normally. The engine momentarily operated at abnormally high torque, with accelerating gas turbine condition, increased gas temperature, decreasing fuel flow, and constant loading—typical of an engine surge. A torque sensor fault was recorded. Within half a second, power dropped significantly and a flameout occurred. The rotor slowed, causing lift loss. An automatic relight sequence restored power after 4 seconds.
The FADEC passed a functional test after data recovery. The HMU was damaged and could not be functionally tested, but physical inspection found no anomalies. A recovered KAflex coupling section showed fractures through all four legs, with features consistent with overstress; no pre-existing cracks or corrosion were noted.
Additional Information
According to the Helicopter Safety Advisory Conference, 497 helicopters operated in the Gulf of Mexico region in 2012. The lessee of SS 208H, EPL Oil & Gas Inc., reported that the platform vented 364 MCF of gas on August 13, 2013. The pilot was not informed of the vented gas. The NTSB referenced a similar accident (CEN11LA252) involving a Bell 206 that ingested methane gas during takeoff, but no probable cause was determined for this accident.