- Location: Recluse, Wyoming
- Accident Number: WPR24FA257
- Date & Time: July 26, 2024, 13:04 Local
- Registration: N357HE
- Aircraft: PILATUS AIRCRAFT LTD PC12/47E
- Aircraft Damage: Destroyed
- Defining Event: Loss of control in flight
- Injuries: 7 Fatal
- Flight Conducted Under: Part 91: General aviation - Personal
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https://data.ntsb.gov/Docket?ProjectID=194777
On July 26, 2024, about 1304 MDT, a Pilatus Aircraft LTD, PC-12/47E airplane, N357HE, was
destroyed when it was involved in an accident near Recluse, Wyoming. The pilot and six
passengers were fatally injured. The airplane was operated as a Title 14 Code of Federal
Regulations Part 91 personal flight.
The pilot and six passengers departed on a cross-country flight on an instrument flight rules
(IFR) flight plan with a planned refueling stop in Montana. The airplane flew on a northwest
course consistent with its planned destination. The airplane leveled off at a maximum cruise
altitude of about 26,000 ft mean sea level (msl).
Satellite imagery indicated that, at the accident site about the time of the accident, cumulus
cloud bases were about 10,000 ft msl with rain showers; and the cloud tops were about 28,500
ft msl. The sounding model indicated trace to light icing with a low probability of supercooled
large droplets (SLD) along about the last 20 minutes of the airplane’s flight path. The accident
airplane was equipped for flight into known icing conditions and likely would not accumulate
much, if any, structural icing from trace to light icing. Additionally, SLDs were likely not a factor
given their low probability of occurrence and the flight profile of the accident airplane during
the last few minutes of flight.
During the last portion of the flight, about 15 seconds before the airplane entered an area of
precipitation as depicted by weather reflectivity charts, the pilot reported a loss of the autopilot
and declared an emergency to the air route traffic control center controller. The controller
asked the pilot where he would like to land and the pilot responded that he was trying to get
control of the airplane; the controller told the pilot to advise if he required additional
assistance. The controller then relayed the minimum IFR altitude and current altimeter setting
with no further response from the pilot.
Data indicate that shortly after entering the area of precipitation, the airplane maneuvered to
the right of course, climbed to about 26,525 ft msl, and entered a 270° right turn. In the first
180° of the turn, the airplane descended to about 25,250 ft msl; however, it climbed to about 27,025 ft msl in the last 90° of the turn. Shortly after, the data showed the airplane made a
slight left turn before it began a descending 180° right turn. The last data point showed the
airplane on a southerly heading, at an altitude of about 21,900 ft msl, and with a groundspeed
of 256 knots.
Sound modeling data indicate that rain shower or thunderstorm activity had the potential for
an updraft speed of up to 3,346 ft/min. ADS-B data indicated that the autopilot disconnected a
few seconds after the airplane encountered the precipitation, likely when the airplane
encountered an updraft because the autopilot was unable to counteract an updraft of the
strength indicated by the modeling data. The airplane was likely operating in instrument
meteorological conditions (IMC) throughout the remainder of the flight.
Following the autopilot disengagement, the pilot had to manually maintain control of the
airplane while operating in IMC, increasing his susceptibility to spatial disorientation. The
airplane’s erratic flight track in the final 2 minutes of flight, culminating in the final rapidly
descending right turn, were consistent with the known effects of spatial disorientation.
Furthermore, the pilot’s focus to re-engage the autopilot likely created an operational
distraction that contributed to a breakdown in his instrument scan.
The airplane likely partially broke up at low altitude during its rapid descent to the ground,
consistent with an exceedance of the airplane’s maximum operating speed. Pieces of the left
wing were found up to 0.82 miles from the main wreckage and exhibited signatures of
overload.
Impact signatures at the accident site, witness observations, and review of the flight data were
all consistent with the pilot losing control of the airplane. Furthermore, postaccident
examination of the airplane wreckage revealed no evidence of preimpact failures or
malfunctions that would have precluded normal operation. Specifically, while the airplane
sustained significant impact damage, the portions of the flight control system that could be
examined showed no evidence of disconnections or preimpact failures. In addition, the
airplane’s setting for the pitch trim was near neutral and for the roll trim was slightly right wing
down.
- Probable Cause: The pilot’s loss of control due to spatial disorientation while operating in instrument meteorological conditions, which resulted in an in-flight breakup. Contributing to the accident was the pilot’s distraction from the autopilot disconnecting due to an updraft from convective activity.
