CEN18FA149

The pilot's loss of helicopter control as a result of fatigue during cruise flight at night.

The helicopter pilot and two emergency medical service crewmembers were on a repositioning flight in night visual meteorological conditions after two helicopter air ambulance flights and a refueling stop. The total flight time for the first three flights was 94 minutes and occurred over a period of about 2 ½ hours. The helicopter departed on the accident flight about 2107. About 1 minute later, the pilot asked the crewmembers whether they were "alright." One crewmember responded "yup" and then asked the pilot, "question is are you alright up there?" The pilot responded, "uhhh think so. Good enough to get us home at least." There was no further discussion related to fatigue. During the flight, the pilot adjusted his seat position and flexed his legs, which were actions consistent with signs of fatigue. Also, although the pilot participated in the medical crewmembers' conversations in the middle of the flight, he did not participate in their conversations near the end of the flight. During the last portion of flight, the helicopter entered a progressively steepening right bank, and the pilot did not respond as the medical crewmembers shouted his name. The helicopter descended and became inverted, and the pilot continued not to respond as the crewmembers' shouted his name. After the helicopter began to roll to the right, the pilot slumped to the left, appearing incapacitated. There was no evidence indicating that the pilot was suffering from a medical condition that could have caused his incapacitation. There was also no evidence of poor quality or quantity of sleep; the pilot's wife reported no issues with the pilot falling asleep or staying asleep, and cellular telephone records and his wife's interview indicated adequate sleep opportunity in the days preceding the accident. On the day of the accident, cellular telephone activity revealed two possible opportunities for the pilot to sleep before going on duty but it is not known if the pilot rested during those times. Thus, the pilot could have been awake for about 15.5 hours at the time of the accident (based on telephone records showing activity at 0725 the morning of the accident) if he did not take advantage of the sleep opportunities. Although this time since awakening would not be considered excessive, this accident shift was the pilot's first after returning from a week-long vacation during which his circadian rhythm would have had him sleeping. Further, the environment created by the helicopter vibration, darkness of night, and few operational demands during the cruise phase of flight would have increased the pilot's fatigue and the body's biological desire to sleep. These factors, along with the pilot's movements observed on the image recorder, indicated that the pilot became fatigued during the flight. Thus, he pilot likely fell asleep during the flight as a result of the time of day, his time since awakening, and the fatigue-inducing effect of the 1 ½ hour flight. No light or audio warnings that would indicate a mechanical malfunction were observed during the accident flight. Postaccident examination and testing revealed no preimpact anomalies that would have precluded normal operation of the helicopter.

The accident flight was the pilot's first flight after a week-long family vacation in Florida. According to cellular telephone records and an interview with the pilot's wife, the pilot had a sleep opportunity of more than 9 hours during each of the 6 nights before the accident. On April 25, 2018, the pilot and his family traveled to Milwaukee, Wisconsin, on an early morning airline flight, had lunch in Milwaukee, and then made the 4-hour drive home. The trip from Florida to Wisconsin involved a change in time zones. Cellular telephone records indicated the pilot's activity from 1655 to 2038 with two extended breaks in activity (greater than 60 minutes) from 1658 to 1801 and from 1802 to 2011. The pilot's wife thought that he went to sleep between about 2100 and 2130. The time that the pilot awoke on the day of the accident was not known. Cellular telephone records indicated his activity from 0725 to 2057 with three extended breaks in activity (greater than 60 minutes) from 0923 to 1118, 1431 to 1556, and 1741 to 2040.The pilot's wife stated that, before going on duty, he would normally rest and sleep during the day, but she did not know if he rested or slept during the day of the accident. The pilot's wife reported no issues with the pilot falling asleep or staying asleep. The pilot's wife, who was also a pilot at Air Methods, was on duty on the day of the accident and worked the day shift. She saw her husband when he arrived at work for the night shift and thought that he had arrived about 45 minutes early for his shift. They did the shift change together, and she noted nothing unusual about her husband. . The University of Wisconsin Anatomic Pathology Laboratory performed an autopsy of the pilot. His cause of death was multiple traumatic injuries. Toxicology testing performed at the Federal Aviation Administration (FAA) Forensic Sciences Laboratory was negative for ethanol and tested-for substances. The helicopter was configured for helicopter air ambulance services. The helicopter was equipped with a radar altimeter and a Honeywell MK XXI enhanced ground proximity warning system. On April 26, 2018, about 2243 central daylight time, a Eurocopter AS350 B2 helicopter, N127LN, was destroyed when it was involved in an accident near Hazelhurst, Wisconsin. The commercial pilot and two emergency medical services crewmembers were fatally injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 repositioning flight. According to the operator, Air Methods Corporation, the pilot and the medical crewmembers transported a patient from the Howard Young Medical Center Heliport (60WI), Woodruff, Wisconsin, to the Merrill Municipal Airport (RRL), Merrill, Wisconsin, departing about 1759 and arriving about 1819. The helicopter then departed from RRL about 1832 with another patient aboard and landed at the UW Hospital and Clinics Heliport (WS27), Madison, Wisconsin, about 1937. The patient was offloaded, and the helicopter departed WS27 about 2028 for refueling at Dane County Regional Airport (MSN), Madison, Wisconsin, arriving about 2037. About 2104, the pilot radioed the operator to report that the helicopter was ready to depart MSN for 60WI. According to information from the helicopter's on-board Appareo Vision 1000 recorder (which records image, audio, and parametric data), the pilot conducted a preflight of the helicopter with the engine operating, and no anomalies were detected. Yawning and sighs were heard. The pilot requested clearance to 60WI and departed about 2107. About 1 minute later, the pilot asked if the medical crew was "alright back there," and one of the medical crewmembers responded "yup." One of the medical crewmembers then stated, "question is are you alright up there?" The pilot responded, "uhhh think so. Good enough to get us home at least." About 2200, a medical crewmember stated, "I could go to sleep," and the pilot responded, "yeah that'd be nice huh." About 2205, the pilot made a radio call to Central Wisconsin Airport's radio frequency. Recorded weather information was heard, and the pilot subsequently made a position announcement. After about 2215, the medical crewmembers started non-aviation-related conversations, and the pilot was last heard during the conversations about 2229. Between about 2215 and 2242, the pilot made movements including raising his left arm near his helmet (which was mounted with night vision goggles), flexing his legs, adjusting his seating position, and changing cyclic position. About 2243, the helicopter was operating in level flight at an airspeed of 126 knots and an altitude of at 2,280 ft mean sea level (msl). The artificial horizon indicator then showed the initiation of a right bank. The pilot's right forearm started moving along with the cyclic to the right, and the artificial horizon indicated a bank between 10° and 15°. The roll rate to the right appeared to increase rapidly, and the pilot's body, right forearm, and right hand (which was holding the base of the cyclic grip) appeared to move along with the increased roll rate. A medical crewmember stated "what are we doin'?" twice. The pilot's head moved to the right and could no longer be seen in the image, and the right bank increased to more than 90°. A medical crewmember stated, in a strained voice, "Ohhh [expletive]." The crewmember then shouted "what?" and the pilot's name. The other medical crewmember also shouted the pilot's name. The pilot's head returned to the image and moved to the left. His right hand still gripped the cyclic. The artificial horizon showed an inverted indication, and the torque gauge indicated a value beyond the red line. The emergency locator transmitter light illuminated while the pilot's head and upper body moved to the left. Sounds similar to a rotor high rpm horn and a grunt were recorded, along with a medical crewmember shouting the pilot's name. The recording contained no response from the pilot when the crewmembers shouted his name. The artificial horizon indicated a right roll of more than 270° with a pitch-down attitude, the altimeter indicated 1,900 ft msl, and the airspeed indicator showed 98 knots. The last two frames showed that the pilot's head and upper body had moved to the right and that the airspeed indicator displayed 70 knots, the artificial horizon indicated a 90° left bank with a pitch-down attitude, and the altimeter indicated 1,825 ft msl. The company's satellite tracking of helicopter showed a normal route of flight until contact was lost at 2243. The helicopter wreckage was found about 0215 the next day. The helicopter was found in a wooded area about 178° and 8.4 nautical miles from 60WI. The wreckage exhibited no signs of fire. A 70-ft-tall tree that was located about 66° and 47 ft from the nose of the wreckage had broken branches. Other trees between that tree and the wreckage had trunks and branches that were broken and linearly separated. A ground impression that was about 11 ft long, 9 ft wide, and 2 ft deep was found in front of the helicopter wreckage. The helicopter came to rest on its right side. The heading of the wreckage from the tail to the nose was about 095°. The smell of fuel was present at the site and in the ground below the helicopter. All major components of the helicopter were located at the site. The cockpit and cabin area was destroyed. The fuselage exhibited rearward crushing deformation. The tailboom was attached to the fuselage. The tail rotor gear box and tail rotor blades remained on the tail. The vertical fin had partially detached from the end of the tailboom. Both horizontal stabilizers were present on the tail. All three rotor blades remained attached to the rotor hub, which was attached to the transmission. The main rotor blades exhibited damage that includes spar fractures and leading edge abrasions and depressions. The main rotor hub rotated when the transmission input drive shaft was manually rot