N810LE

HISTORY OF FLIGHTOn September 19, 2013, about 2127 central daylight time, a Eurocopter AS350B2 emergency medical service (EMS) configured helicopter, N810LE, experienced a hard landing in a field following a total loss of engine power near Canton, Mississippi. The airline transport pilot incurred serious injury and the two medical flight crewmembers and a passenger incurred minor injuries. The helicopter was owned and operated by Metro Aviation Inc., under the provisions of Title 14 Code of Federal Regulations Part 135 as an on-demand Emergency Medical Services flight. The intent of the flight was a patient transfer. Night visual meteorological conditions prevailed for the medical patient transfer flight and a company visual flight rules flight plan was filed. The flight originated from a private hospital helipad in Ackerman, Mississippi, at 2054, with the intended destination of Jackson, Mississippi.

According to the pilot, about 10 minutes after departure, a low engine oil pressure indicator warning light illuminated and the oil pressure gauge indicated between 0 and 2 psi. He noted that there was no rise in the oil temperature indication or engine temperature indicator and continued toward the intended destination while attempting to verify the loss of engine oil pressure. Several minutes later the pilot noticed a low torque indication and again noted that there was no rise in the oil temperature or engine temperature. About 25 minutes after departure, the pilot saw a rise in the engine temperature gauge and subsequently lowered the collective. He then observed the engine temperature rising at a higher rate and located an open field in order to perform an off airport landing. The engine lost total power prior to reaching the open field and the pilot performed an autorotation. After impacting the ground, the pilot performed the emergency shutdown procedures. In addition, the pilot stated that he was using night vision goggles during the accident flight.

According to a witness, as the helicopter was departing the helipad there was "dark black" smoke coming out of the engine exhaust at the back of the helicopter. The smoke was "heaviest when [the helicopter] tilted to go west." In addition, the helicopter started to make a "clanking" noise as it accelerated away from the helipad. As it departed the area, the helicopter continued to fly forward without making any type of turn. PERSONNEL INFORMATIONAccording to the pilot and Federal Aviation Administration (FAA) records, he held an airline transport pilot certificate for airplane multiengine land, a commercial pilot certificate for airplane single-engine land, helicopter, and instrument helicopter. In addition, he held a flight instructor certificate for airplane multiengine and single-engine land, helicopter, and instrument. He also held an advanced ground instructor, instrument ground instructor, and flight engineer certificate. He held a first-class medical certificate, which was issued on August 8, 2013. He had accumulated 3,380 total hours of flight experience, 1,200 hours of flight experience in helicopters, and 77 of those hours were in the same make and model as the accident helicopter. AIRCRAFT INFORMATIONAccording to FAA records the helicopter was issued an airworthiness certificate in 2010 and was registered to Metro Aviation Inc. on May 27, 2010. It was powered by a Turbomeca Arriel 1D1 series, 732-shaft horsepower engine.

The helicopter's most recent maintenance inspection, under the approved inspection program, was completed on September 13, 2013, which was about 12 flight hours prior to the accident. The maintenance inspection included a replacement of the second stage turbine disk (T2) in the engine. The engine manufacturer required that a maintenance center level III technician had to perform the replacement of the T2 on the engine. The maintenance technician was required to have and did have manufacturer specific engine training and utilize a maintenance technical instruction manual provided by the engine manufacturer for the T2 replacement. During the replacement of the T2, the maintenance manual stated that the preliminary procedures required the technician to "clean the rear bearing – free turbine nozzle guide vane assy." During the maintenance, the rear bearing had been judged "clean" by the maintenance technician and no cleaning had been carried out. However, review of manufacturer's maintenance procedures required a systematic cleaning of the rear bearing when the T2 was replaced every 4,000 cycles no matter the condition of the bearing. The recorded cycles on the T2 was 3990.58 at the time of the T2 replacement.

Engine Oil System

The engine oil system consisted of a tank, which held 5.7 liters of oil, pumps, a filter, strainers, a cooler, breather, and indicating devices. The gas generator rear bearing was lubricated by oil passing through an external tube, then through a restrictor, and a tube screwed into the bearing housing. The oil coated the bearing, lubricated it, and the bearing housing was sealed by pressurized labyrinth seals. Then the oil traveled by gravity to the bottom of the housing, through a tube in the bottom of the casing, an external tube, through a strainer, then finally through the scavenge pump. During the lubrication process, the air/oil mist that resulted from lubrication passed through a tube connected to the rear bearing housing and an external tube, which vented any excess air/oil mist or over pressurization of the gas generator rear bearing housing into the exhaust of the engine. AIRPORT INFORMATIONAccording to FAA records the helicopter was issued an airworthiness certificate in 2010 and was registered to Metro Aviation Inc. on May 27, 2010. It was powered by a Turbomeca Arriel 1D1 series, 732-shaft horsepower engine.

The helicopter's most recent maintenance inspection, under the approved inspection program, was completed on September 13, 2013, which was about 12 flight hours prior to the accident. The maintenance inspection included a replacement of the second stage turbine disk (T2) in the engine. The engine manufacturer required that a maintenance center level III technician had to perform the replacement of the T2 on the engine. The maintenance technician was required to have and did have manufacturer specific engine training and utilize a maintenance technical instruction manual provided by the engine manufacturer for the T2 replacement. During the replacement of the T2, the maintenance manual stated that the preliminary procedures required the technician to "clean the rear bearing – free turbine nozzle guide vane assy." During the maintenance, the rear bearing had been judged "clean" by the maintenance technician and no cleaning had been carried out. However, review of manufacturer's maintenance procedures required a systematic cleaning of the rear bearing when the T2 was replaced every 4,000 cycles no matter the condition of the bearing. The recorded cycles on the T2 was 3990.58 at the time of the T2 replacement.

Engine Oil System

The engine oil system consisted of a tank, which held 5.7 liters of oil, pumps, a filter, strainers, a cooler, breather, and indicating devices. The gas generator rear bearing was lubricated by oil passing through an external tube, then through a restrictor, and a tube screwed into the bearing housing. The oil coated the bearing, lubricated it, and the bearing housing was sealed by pressurized labyrinth seals. Then the oil traveled by gravity to the bottom of the housing, through a tube in the bottom of the casing, an external tube, through a strainer, then finally through the scavenge pump. During the lubrication process, the air/oil mist that resulted from lubrication passed through a tube connected to the rear bearing housing and an external tube, which vented any excess air/oil mist or over pressurization of the gas generator rear bearing housing into the exhaust of the engine. WRECKAGE AND IMPACT INFORMATIONThe helicopter came to rest upright in an open field that was surrounded by trees. Postaccident examination of the landing gear crosstubes revealed that they were bowed downward. The tailboom separated from the helicopter and came to rest just aft of the fuselage. The main rotor blades remained intact and attached to the rotorhead. ADDITIONAL INFORMATIONAccording to the pilot, he had an intermittent oil pressure gauge issue in a different helicopter a "couple of weeks" prior to the accident flight so "[he] thought this was a similar issue at first."

According to FAA Publication "Pilot's Handbook of Aeronautical Knowledge," (FAA-H-8083-25A) that "for the past several decades, research into how people actually make decisions has revealed that when pressed for time, experts faced with a task loaded with uncertainty, first assess whether the situation strikes them as familiar. Rather than comparing the pros and cons of different approaches, they quickly imagine how one or a few possible courses of action in such situations will play out. Experts take the first workable option they can find. While it may not be the best of all possible choices, it often yields remarkably good results.

The terms naturalistic and automatic decision-making have been coined to describe this type of decision-making. The ability to make automatic decisions holds true for a range of experts from fire fighters to chess players. It appears the expert's ability hinges on the recognition of patterns and consistencies that clarify options in complex situations. Experts appear to make provisional sense of a situation, without actually reaching a decision, by launching experience-based actions that in turn trigger creative revisions.

This is a reflexive type of decision-making anchored in training and experience and is most often used in times of emergencies when there is no time to practice analytical decision-making. Naturalistic or automatic decision-making improves with training and expe...