CEN17FA168

The pilot's loss of airplane control due to spatial disorientation during the initial climb after takeoff in night instrument meteorological conditions and moderate turbulence.

The pilot and two medical crewmembers departed on an air ambulance flight in night instrument meteorological conditions to pick up a patient. After departure, the local air traffic controller observed the airplane's primary radar target with an incorrect transponder code in a right turn and climbing through 4,400 ft mean sea level (msl), which was 800 ft above ground level (agl). The controller instructed the pilot to reset the transponder to the correct code, and the airplane leveled off between 4,400 ft and 4,600 ft msl for about 30 seconds. The controller then confirmed that the airplane was being tracked on radar with the correct transponder code; the airplane resumed its climb at a rate of about 6,000 ft per minute (fpm) to 6,000 ft msl. The pilot changed frequencies as instructed, then contacted departure control and reported "with you at 6,000 [ft msl]" and the departure controller radar-identified the airplane. About 1 minute later, the departure controller advised the pilot that he was no longer receiving the airplane's transponder; the pilot did not respond, and there were no further recorded transmissions from the pilot. Radar data showed the airplane descending rapidly at a rate that reached 17,000 fpm. Surveillance video from a nearby truck stop recorded lights from the airplane descending at an angle of about 45° followed by an explosion. The airplane impacted a pasture about 1.5 nautical miles south of the airport, and a postimpact fire ensued. All major components of the airplane were located within the debris field. Ground scars at the accident site and damage to the airplane indicated that the airplane was in a steep, nose-low and wings-level attitude at the time of impact. The airplane's steep descent and its impact attitude are consistent with a loss of control. An airplane performance study based on radar data and simulations determined that, during the climb to 6,000 ft and about 37 seconds before impact, the airplane achieved a peak pitch angle of about 23°, after which the pitch angle decreased steadily to an estimated -42° at impact. As the pitch angle decreased, the roll angle increased steadily to the left, reaching an estimated -76° at impact. The performance study revealed that the airplane could fly the accident flight trajectory without experiencing an aerodynamic stall. The apparent pitch and roll angles, which represent the attitude a pilot would "feel" the airplane to be in based on his vestibular and kinesthetic perception of the components of the load factor vector in his own body coordinate system, were calculated. The apparent pitch angle ranged from 0° to 15° as the real pitch angle steadily decreased to -42°, and the apparent roll angle ranged from 0° to -4° as the real roll angle increased to -78°. This suggests that even when the airplane was in a steeply banked descent, conditions were present that could have produced a somatogravic illusion of level flight and resulted in spatial disorientation of the pilot. Analysis of the performance study and the airplane's flight track revealed that the pilot executed several non-standard actions during the departure to include: excessive pitch and roll angles, rapid climb, unexpected level-offs, and non-standard ATC communications. In addition to the non-standard actions, the pilot's limited recent flight experience in night IFR conditions, and moderate turbulence would have been conducive to the onset of spatial disorientation. The pilot's failure to set the correct transponder code before departure, his non-standard departure maneuvering, and his apparent confusion regarding his altitude indicate a mental state not at peak acuity, further increasing the chances of spatial disorientation. A postaccident examination of the flight control system did not reveal evidence of any preimpact anomalies that would have prevented normal operation. The engine exhibited rotational signatures indicative of engine operation during impact, and an examination did not reveal any preimpact anomalies that would have precluded normal engine operation. The damage to the propeller hub and blades indicated that the propeller was operating under high power in the normal range of operation at time of impact. Review of recorded data recovered from airplane's attitude and heading reference unit did not reveal any faults with the airplane's attitude and heading reference system (AHRS) during the accident flight, and there were no maintenance logbook entries indicating any previous electronic attitude director indicator (EADI) or AHRS malfunctions. Therefore, it is unlikely that erroneous attitude information was displayed on the EADI that could have misled the pilot concerning the actual attitude of the airplane. A light bulb filament analysis of the airplane's central advisory display unit (CADU) revealed that the "autopilot disengage" caution indicator was likely illuminated at impact, and the "autopilot trim" warning indicator was likely not illuminated. A filament analysis of the autopilot mode controller revealed that the "autopilot," "yaw damper," and "altitude hold" indicators were likely not illuminated at impact. The status of the "trim" warning indicator on the autopilot mode controller could not be determined because the filaments of the indicator's bulbs were missing. However, since the CADU's "autopilot trim" warning indicator was likely not illuminated, the mode controller's "trim" warning indicator was also likely not illuminated at impact.  Exemplar airplane testing revealed that the "autopilot disengage" caution indicator would only illuminate if the autopilot had been engaged and then disconnected. It would not illuminate if the autopilot was off without being previously engaged nor would it illuminate if the pilot attempted and failed to engage the autopilot by pressing the "autopilot" pushbutton on the mode controller. Since the "autopilot disengage" caution indicator would remain illuminated for 30 seconds after the autopilot was disengaged and was likely illuminated at impact, it is likely that the autopilot had been engaged at some point during the flight and disengaged within 30 seconds of the impact; the pilot was reporting to ATC at 6,000 ft about 30 seconds before impact and then the rapid descent began. The airplane was not equipped with a recording device that would have recorded the operational status of the autopilot, and the investigation could not determine the precise times at which autopilot engagement and disengagement occurred. However, these times can be estimated as follows: • The pilot likely engaged the autopilot after the airplane climbed through 1,000 ft agl about 46 seconds after takeoff, because this was the recommended minimum autopilot engagement altitude that he was taught. • According to the airplane performance study, the airplane's acceleration exceeded the autopilot's limit load factor of +1.6g about 9 seconds before impact. If it was engaged at this time, the autopilot would have automatically disengaged. • The roll angle data from the performance study were consistent with engagement of the autopilot between two points: 1) about 31 seconds before impact, during climb, when the bank angle, which had stabilized for a few seconds, started to increase again and 2) about 9 seconds before impact, during descent, at which time the autopilot would have automatically disengaged. Since the autopilot would have reduced the bank angle as soon as it was engaged and there is no evidence of the bank angle reducing significantly between these two points, it is likely that the autopilot was engaged closer to the latter point than the former. Engagement of the autopilot shortly before the latter point would have left little time for the autopilot to reduce the bank angle before it would have disengaged automatically due to exceedance of the normal load factor limit.

A review of FAA medical records indicated that the pilot reported no significant medical concerns to the FAA, and as of the most recent medical examination the medical examiner identified no significant conditions on physical examination. South Plains Forensic Pathology, P.A., Lubbock, Texas, completed an autopsy on the pilot. The autopsy report concluded that the cause of death was multiple blunt impact injuries. The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicological tests on specimens that were collected during the pilot's autopsy. Results were negative for all tests conducted. Preflight Weather Briefing – ForeFlight At 2303, the pilot retrieved a ForeFlight weather briefing for the accident flight and he filed an IFR flight plan. the ForeFlight briefing would have displayed in the ForeFlight app and been emailed to the pilot immediately after the flight plan was filed. The pilot also viewed multiple weather images before the flight, but the specific items viewed by the pilot are not logged by ForeFlight. Archived Weather Data At 2353, AMA reported wind from 360° at 21 knots with gusts to 28 knots, visibility of 10 statute miles or greater, ceiling broken at 700 ft agl, overcast cloud base at 1,200 ft agl, temperature of 7°C, dew point temperature of 7°C, and an altimeter setting of 29.78 inches of mercury. The remarks section of the 2353 observation included: station with a precipitation discriminator, peak wind of 32 knots from 360° occurred at 2326, lightning more than 10 miles away to the west, rain began at 2314 and ended at 2325, and ceiling variable between 500 ft agl and 900 ft agl. Data from the AMA weather radar indicated light values of reflectivity around the accident location. A radial velocity image from around the time of the accident identified veering wind (wind that turns clockwise with increasing height) in the lowest 10,000 ft msl around the accident location. A wind profile for AMA around the accident time indicated that, near the accident location, the wind at 4,000 and 5,000 ft msl was from the north-northeast at 35 knots; the wind at 6,000 ft msl was from the northeast at 30 knots; the wind at 7,000 ft msl was from the east at 30 knots; the wind at 8,000 ft msl was from the southeast at 35 knots; and the wind at 9,000 ft msl was from the south-southeast at 45 knots. The graphical turbulence guidance (GTG) depicted the probability of clear air turbulence at altitudes of 3,000, 5,000, 7,000, and 9,000 ft msl, applicable to times surrounding the accident. These images depicted mainly light-to-moderate turbulence over AMA. The GTG is not intended to predict turbulence associated with convection and thunderstorm clouds but may provide some guidance in areas of properly predicted thunderstorms when the convection is widespread. A high-resolution rapid refresh model sounding for the accident location at 0000 on April 29, 2017, revealed that the near-surface wind was from the north-northeast about 20 knots. About 5,500 ft msl, the wind was from the northeast about 30 knots. Above this level, the wind veered with height and increased in magnitude to a south wind at 45 knots about 11,000 ft msl. A temperature inversion was noted between 6,200 ft and 7,800 ft msl, and the freezing level was near 13,000 ft msl. Calculations made by the rawinsonde observation program identified a layer of significant turbulence between about 5,500 and 12,600 ft msl. Relative humidity was greater than 90% between near the surface and about 10,000 ft msl and in a layer between about 16,000 and 18,000 ft msl. The warning coordination meteorologist for the National Weather Service (NWS) Weather Forecast Office (WFO) in Amarillo, Texas, provided a 3D image (figure 3, which shows AMA at the center of the 3D box) that showed a wind shear zone between 2,500 and 3,500 ft msl as seen from the AMA weather radar about 2355. The red area indicates wind away from the radar, and the green area indicates wind toward the radar. The image shows a northerly wind near the surface and a 40 to 60 knot southerly wind above 4,000 ft msl. There were no publicly disseminated pilot reports for AMA for altitudes below 10,000 ft msl between 2100 on April 28, 2017, and 0300 on April 29, 2017. Figure 3 – Wind profile, 3D view At 2036, a terminal aerodrome forecast was issued for AMA by the NWS WFO in Amarillo that forecasted for the accident time: wind from 020° at 17 knots with gusts to 25 knots, visibility greater than 6 miles, light rain showers, scattered clouds at 3,000 ft agl, and ceiling overcast at 5,000 ft agl. At 2145, an AIRMET SIERRA was issued for IFR conditions and precipitation/mist below 10,000 ft msl for an area that included the accident location. At the accident time, there were no AIRMETs active for turbulence or low level wind shear potential below 10,000 ft msl that included the accident location. At 2145, an AIRMET TANGO was issued for moderate turbulence between 10,000 ft msl and FL180 for an area that included the accident location. There were no convective or non-convective SIGMET advisories active at the accident time that included the accident location. A convective SIGMET was issued at 2255 for an area that was very close to the accident location. According to the National Oceanic and Atmospheric Administration's Aviation Weather Center (AWC), "any Convective SIGMET implies severe or greater turbulence, severe icing, and low level wind shear." Further, according to discussion with AWC staff, convective SIGMETs are not geographically static for their valid period, rather they should move with any movement vector included in that convective SIGMET. NWS Instruction 10-811 and FAA Advisory Circular (AC) 00-45H both address the "movement" field (e.g., "MOV FROM 24045KT") in the text of a convective SIGMET. AC 00-45H provides the following translation for the portion of the convective SIGMET containing the movement field: "an intensifying area of severe thunderstorms moving from 240° at 45 knots (to the northeast)." According to the Domestic Operations Branch Chief at the AWC, "on occasion when the thunderstorm cells contained in the [convective SIGMET] are moving in vastly different direction than the [convective SIGMET], we add a comment at the bottom of the [convective SIGMET] something like 'CELL MOV FROM 22040KT.' Of course, we don't include all comment options in the NWS Directives, so most people don't know this." Other Flight Crew Reports Flight crewmembers of several different airplanes that arrived and departed AMA within about 1 hour of the accident time were contacted regarding turbulence and/or weather conditions encountered on the approach to/departure from AMA. The first officer of an Embraer 170 airplane that landed at AMA about 40 minutes before the accident time reported no significant weather conditions. The flight crew of an Embraer 145 airplane that landed at AMA about 25 minutes before the accident time reported that they encountered light chop to light turbulence. The crew did not remember giving or being asked for any PIREPs. The flight crew of a Boeing 737 airplane that departed AMA about 1 hour after the accident time reported that they were concerned about the weather in the area. There was some drizzle as they taxied out. They were concerned about ice and storms in the area. They experienced moderate to heavy turbulence during the climb-out, and there were isolated storm cells to the east. They did not experience ice buildup on the airplane, but they deviated for weather as they departed to the east. The captain said, "it wasn't the worst turbulence he had been in, but it was close." The first officer said that the moderate- to-heavy turbulence from the time they departed until climbing through 10,000 ft msl was some of the worst turbulence he had experienced. The onboard weather radar was solid gr