N369TLRobinson Helicopter R44 II · 2006

On January 19, 2012, at 0901 central standard time, a Robinson R44 II, N369TL, collided with trees while maneuvering at low altitude and impacted the Belle Isle salt dome, about 12 miles south of Centerville, Louisiana. There was a fire after impact. The pilot and the pilot-rated passenger were fatally injured. The helicopter was substantially damaged. The helicopter was registered to and operated by CENAC Marine Services, LLC, Houma, Louisiana, under the provisions of 14 Code of Federal Regulations (CFR) Part 91 as a personal flight. Visual meteorological conditions (VMC) prevailed at the time of the accident, and no flight plan had been filed. The local flight originated from Houma (KHUM), Louisiana, at 0827.

Several witnesses told St. Mary’s Parish sheriff’s deputies that they saw the helicopter circling at a low altitude. They said the left seat pilot waved at them. None of the witnesses saw the impact, but heard the impact and saw smoke. They responded to the site and used portable fire extinguishers to extinguish the fire.

According to the helicopter owner/operator the pilot-in-command, age 40, was seated in the left seat. He held an airline transport pilot certificate with airplane multiengine land rating, commercial pilot privileges with airplane single-engine land and rotorcraft-helicopter ratings, and a flight instructor certificate with airplane single/multiengine and instrument ratings. He was type rated in the Beech 300/350 King Air, Hawker Beechjet 400, Cessna 500 Citation, and the Mitsubishi MU-300 Diamond. He held a first class airman medical certificated, dated June 24, 2011, with no restrictions or limitations. According to his employer, the pilot had logged 8,700 total flight hours and 260 hours in the Robinson R44, of which 215 hours were as pilot-in-command. His list flight review was accomplished in the Beech 350 King Air on December 6, 2011.

The second pilot, age 43, was seated in the right seat. He held a private pilot certificate with a rotorcraft-helicopter rating. He also held a third class airman medical certificate, dated April 15, 2010, with the restriction that he wear corrective lenses while exercising the privileges of his airman certificate. According to his employer, the pilot had logged 450 total flight hours, the majority of which was in the Bell 47 helicopter. He had logged 18.9 hours in the Robinson R44, his last flight being on May 5, 2011. He had also flown the Brantley helicopter.

N369TL (serial number 11055), a model R44 II, was manufactured by the Robinson Helicopter Company on January 16, 2006. It was powered by a Lycoming IO-540-AE1A5 engine (serial number L-30804-48A), rated at 300 horsepower. According the helicopter maintenance records, the last 100-hour/annual inspection was performed on March 31, 2011, at a total time of 461.5 hours.

The following METARs (Aviation Routine Weather Report) were recorded at Houma (KHUM) and Patterson (KPTN), Louisiana:

KHUM 0850: Wind, 020 degrees at 3 knots; visibility, 6 miles, mist; ceiling, 1,800 feet broken; temperature, 12 degrees Celsius (C.); dew point, 11 degrees C.; altimeter, 30.15 inches of Mercury.

KPTN 0855: Wind, 070 degrees at 3 knots; visibility, 10 miles; ceiling, 2,400 feet overcast; temperature, 12 degrees C.; dew point, 11 degrees C.; altimeter, 30.14 inches of Mercury.

The accident site was situated at an elevation of 6 feet msl (above mean sea level), encompassing a perimeter of about 500 feet. The on-scene investigation revealed the helicopter struck several trees and fell straight to the ground in a nose-low attitude, coming to rest on its right side. A post-impact fire ensued. The tail boom and tail rotor blades remained attached to the helicopter, and 3-foot stubs of the main rotor blades remained attached. The tail rotor drive shaft was intact and, when turned by hand, continuity was observed. Nearby was a 2-foot gash deep in the ground, about the length of a main rotor blade. The helicopter sustained extensive thermal damage from the tail boom forward. All control rods and linkages remained attached to the rotor hub. All breaks were consistent with overload fractures.

The instrument panel was destroyed, but the vertical speed indicator registered 2,600 feet per minute descent, and the attitude indicator revealed a 35-degree left turn and nose-down attitude.

Impact signatures were consistent with the helicopter in a steep descent and the engine operating at the time of impact.

Autopsies were performed on both pilots by the Louisiana Forensic Center. According to their reports, both pilots succumbed to blunt force injuries.

Toxicology protocols were conducted by FAA’s Civil Aeromedical Institute (CAMI). According to their reports, none of the pilot’s specimens were suitable for analysis due to putrefaction. The pilot-rated passenger had no carbon monoxide, cyanide or ethanol in the blood (cavity)`, but amlodipine, pravastatin, and valsartan were detected in the liver and blood (cavity). According to FAA’s Forensic Toxicology Drug Information website, amlodipine (Norvasc®) is a prescription calcium channel blocker medication used to treat high blood pressure and angina, pravastatin (Pravachol®) is a prescription HMG-CoA reductase inhibitor to reduce cholesterol biosynthesis and treat elevated blood lipids, and valsartan (Diovan®) is a prescription angiotensin II receptor blocker (ARB) that acts on the AT1 receptor subtype and is used to control high blood pressure.

The engine was examined at Air Salvage of Dallas in Lancaster, Texas, under the auspices of the National Transportation Safety Board. Examination revealed that the intake and exhaust valves were seized due to thermal damage to the engine. There were no pre-impact anomalies with the engine which would have precluded normal operation.

The three servos were examined at the Robinson Helicopter Company under the auspices of the National Transportation Safety Board. Thermal damaged had compromised most of the servo seals. No foreign debris, scoring, or witness marks were observed on either spool or metering edges of the sleeve.

The Federal Aviation Administration (FAA) inspector who participated in the investigation, a former U.S. Army helicopter pilot and an FAA helicopter pilot examiner, submitted a written statement in which he noted what appeared to be a high velocity impact, large grooves in the ground indicating engine power at impact, and a near vertical descent consistent with “settling with power.”

The following is based on FAA’s “Helicopter Flying Handbook,” (FAA-H-8083-21, Chapter 11, p. 11-13):

“Vortex ring state” is an aerodynamic condition in which a helicopter may be in a vertical descent with 20 percent up to maximum power applied, and little or no climb performance. “Settling with power” occurs when the helicopter keeps settling even though full engine power is applied. Main rotor tip vortices generate drag and degrade airfoil efficiency. As long as the tip vortices are small, their only effect is a small loss in main rotor efficiency. However, when the helicopter begins to descend vertically, it settles into its own downwash, which greatly enlarges the tip vortices. In this vortex ring state, most of the power developed by the engine is wasted in circulating the air in a doughnut pattern around the rotor. A vortex ring state may be entered during any maneuver that places the main rotor in a condition of descending in a column of disturbed air and low forward airspeed. Airspeeds that are below translational lift airspeeds are within this region of susceptibility to settling with power aerodynamics. This condition is sometimes seen during quick-stop type maneuvers or during recovery from autorotation.

Some of the situations that are conducive to a settling with power condition are hovering above ground effect altitude, specifically attempting to hover out of ground effect (OGE) at altitudes above the hovering ceiling of the helicopter, attempting to hover OGE without maintaining precise altitude control, pinnacle or rooftop helipads when the wind is not aligned with the landing direction, and downwind and steep power approaches in which airspeed is permitted to drop below 10 knots, depending on the type of helicopter.