ERA13FA253

The pilot's loss of control due to spatial disorientation in instrument meteorological conditions, which resulted in an exceedance of the airplane's design stress limitations, and a subsequent in-flight breakup.

The volunteer medical transport flight was established on course toward an en route navigational fix. Upon reaching the fix, the flight was expected to continue toward the initial approach fix at the destination airport in preparation for an instrument approach; however, about 5 miles southeast of the en route fix, the airplane began to deviate off course. When asked by an air traffic controlller about the reason for the deviation, the pilot stated that the airplane had turned "the wrong way" and indicated that he had incorrectly loaded the instrument approach into the airplane's GPS. The controller provided a vector to the pilot to return the airplane to the previously established course, and the pilot acknowledged. About 1 minute later, radar contact with the airplane was lost. Radar data indicated that the airplane entered a rapidly-descending left turn in the final moments of the flight during which it reached an estimated 80-degree left bank, lost about 3,700 feet of altitude in 36 seconds, and accelerated to an airspeed of about 240 knots before breaking up. All fracture surfaces exhibited failure characteristics consistent with overload. Examination of the engines revealed no anomalies. Analysis of weather information for the area of the accident site indicated that the airplane was likely operating in instrument meteorological conditions at the time of the accident but that icing conditions likely were not present in the immediate vicinity. The restricted visibility, turbulence, the airplane's unexpected off-course turn, the pilot's resulting distraction with the operation and configuration of the GPS, and possibly his sudden need to fly the airplane without the aid of the autopilot would have been conducive to the development of spatial disorientation. The resulting ground track, rapid turning descent, and breakup were consistent with a loss of control as a result of spatial disorientation.

Performance Studies Performance and trajectory studies were conducted to determine the accident airplane's altitude, speed, and rate of descent about the time of the breakup. Correlation of radar data indicated that during the last minute of the flight, the airplane was established on a northerly track at an altitude of 8,300 feet msl and airspeed of about 130 knots. The airplane descended in a left spiraling turn, lost about 3,700 feet of altitude in 36 seconds, and accelerated to an airspeed of about 240 knots prior to the breakup. A trajectory model utilizing the distribution of the wreckage, the approximate airspeed obtained from the radar performance study, and the wind conditions present at the time of the accident, produced results consistent with a breakup at an altitude near 4,600 feet msl, about 3,600 feet agl. According to the manufacturer's pilot operating handbook, the airplane's never exceed speed (Vne) was 195 knots, and its design maneuvering speed (Va) was 138 knots at maximum gross weight. Spatial Disorientation The FAA publication Medical Facts for Pilots (AM-400-03/1), described several vestibular illusions associated with the operation of aircraft in low visibility conditions. Somatogyral illusions, those involving the semicircular canals of the vestibular system, were generally placed into one of four categories, one of which was the "graveyard spiral." According to the text, the graveyard spiral, "…is associated with a return to level flight following an intentional or unintentional prolonged bank turn. For example, a pilot who enters a banking turn to the left will initially have a sensation of a turn in the same direction. If the left turn continues (~20 seconds or more), the pilot will experience the sensation that the airplane is no longer turning to the left. At this point, if the pilot attempts to level the wings this action will produce a sensation that the airplane is turning and banking in the opposite direction (to the right). If the pilot believes the illusion of a right turn (which can be very compelling), he/she will reenter the original left turn in an attempt to counteract the sensation of a right turn. Unfortunately, while this is happening, the airplane is still turning to the left and losing altitude. Pulling the control yoke/stick and applying power while turning would not be a good idea–because it would only make the left turn tighter. If the pilot fails to recognize the illusion and does not level the wings, the airplane will continue turning left and losing altitude until it impacts the ground." The Airplane Flying Handbook (FAA-H-8083-3A) described some hazards associated with flying when the ground or horizon are obscured. "The vestibular sense (motion sensing by the inner ear) in particular tends to confuse the pilot. Because of inertia, the sensory areas of the inner ear cannot detect slight changes in the attitude of the airplane, nor can they accurately sense attitude changes that occur at a uniform rate over a period of time. On the other hand, false sensations are often generated; leading the pilot to believe the attitude of the airplane has changed when in fact, it has not. These false sensations result in the pilot experiencing spatial disorientation." An autopsy was performed on the pilot on May 27, 2013 at the Albany Medical Center in Albany, NY. The cause of death was listed as "massive traumatic blunt force injuries." Toxicological testing was performed on the pilot by the FAA Bioaeronautical Sciences Research Laboratory in Oklahoma City, Oklahoma. Testing was negative for carbon monoxide and ethanol. Losartan, an FAA-accepted high blood pressure medication, was detected in muscle and liver samples. The pilot reported use of this medication on his most recent FAA medical certificate application. The 1653 weather observation at RME, located about 40 miles northwest of the accident site, included winds from 330 degrees magnetic at 8 knots, 10 statute miles visibility in light rain, broken cloud layers at 2,300 and 2,800 feet, overcast clouds at 3,700 feet, temperature 7 degrees C, dew point 4 degrees C, and an altimeter setting of 30.06 inches of mercury. Schenectady County Airport (SCH), Schenectady, New York, was located about 27 miles to the east-southeast of the accident site. A human-augmented report issued at 1645 included wind from 320 degrees at 8 knots gusting to 16 knots, 7 statute miles visibility, overcast clouds at 2,600 feet, temperature 8 degrees C, dew point 7 degrees C, and an altimeter setting of 29.96 inches of mercury. ALB was located approximately 36 miles to the east-southeast of the accident site. The 1651 observation included wind from 310 degrees at 9 knots, 1.5 statute miles visibility, runway 1 visual range variable between 5,000 and 6,000 feet, rain, mist, and overcast clouds at 800 feet, variable between 500 and 1,100 feet. An upper air sounding retrieved from a rawinsode launch at 2000 in Albany, New York indicated that the majority of the troposphere was stable or conditionally unstable. A temperature inversion was noted between 5,700 and 7,400 feet. The freezing level was approximately 4,300 feet, with the potential for moderate icing near 10,000 and 14,000 feet. A wind profile indicated a generally northerly wind from 1,000 feet to 7,500 feet, with magnitudes between 12 and 24 knots, and a potential for significant turbulence near 7,500 feet. Weather radar imagery from Albany, New York, about the time of the accident, depicted light values of reflectivity over much of the area surrounding the accident site with moderate values immediately to the west and southwest of the accident site. Imagery identified the presence of "big drops" of rain in the vicinity of the accident site, with wet snow and snow pellets to the west of the accident site, indicative of melting snow in the area. Airmen's Meteorological Information (AIRMET) advisories, issued at 1645 for IMC and mountain obscuration, moderate turbulence below 8,000 feet, and moderate icing between the freezing level and 22,000 feet, were valid for the region surrounding the accident site. The Area Forecast for northeastern New York issued at 1331 and valid for the accident time predicted overcast cloud ceilings at 1,000 to 2,000 feet with cloud tops to 18,000 feet, surface visibility 3-5 miles, light rain, and mist. There were no records of the pilot obtaining a weather briefing from Lockheed Martin Flight Services, DTC DUAT, or CSC DUATs weather information services. Review of data provided by a third-party internet flight planning and weather briefing service showed that the pilot filed the flight plan for the accident flight about 1020 the morning of the accident. The pilot also accessed a weather radar summary map for the route of the accident flight at this time. The debris field measured approximately one mile in length, beginning on the southeast side of Garoga Reservoir, continuing to the north side of the reservoir, and was oriented on a heading of approximately 360 degrees magnetic. Portions of the empennage, sections of the left wing, and portions of the fuselage skin were located south of the reservoir. The main wreckage came to rest in the reservoir. The left engine was found on the north side of the reservoir. (See figure 1.) Wreckage Diagram Figure 1 - Wreckage Diagram The main wreckage consisted of the majority of the fuselage, the right wing, and right engine. The aft fuselage sides and roof section were separated from the main wreckage, and the forward roof section was also separated, but was recovered with the main wreckage. The forward baggage door was in place and found in the latched position. The right wing remained attached at its root, and displayed significant impact damage along its entire span. The aileron remained attached, and control continuity was confirmed to the cockpit. The wing flap remained attache