Loss of control in flight: Pilatus PC-12/47E, N357HE, fatal accident occurred on July 26, 2024, near Recluse, Wyoming

• 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

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194777/pdf

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.

Aerodynamic stall/spin: Lockheed 12A Electra Junior, N93R, fatal accident occurred on June 15, 2024, at Chino Airport (CNO/KCNO), Chino, California

• Location: Chino, California 
• Accident Number: WPR24FA196 
• Date & Time: June 15, 2024, 12:36 Local
• Registration: N93R 
• Aircraft: Lockheed 12A 
• Aircraft Damage: Substantial
• Defining Event: Aerodynamic stall/spin 
• Injuries: 2 Fatal 
• Flight Conducted Under: Part 91: General aviation - Personal 

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194475/pdf

https://data.ntsb.gov/Docket?ProjectID=194475

On June 15, 2024, about 1236 Pacific daylight time, a Lockheed 12A airplane, N93R, was substantially damaged when it was involved in an accident near Chino, California. The pilot and co-pilot were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The accident flight was conducted before a Father’s Day event to prepare for a planned threeairplane formation flight later that day. During the morning briefing, the pilot and co-pilot were assigned to the accident airplane. A representative of the operator believed that the co-pilot extended the flaps during a functional test as part of the preflight inspection. Ground crew members subsequently observed the flaps extended during engine start and warned the flight crew using hand and arm signals; however, the flight crew did not acknowledge the warning. Witness observations indicated that the flaps remained fully extended during taxi and takeoff, and video evidence showed that the flaps remained extended during the initial climb. 

The operator reported that crews commonly used reduced engine power on hot days to reduce engine oil temperatures and engine noise. After takeoff, the airplane climbed to approximately 200 to 300 ft above ground level (agl); it then pitched up, turned left, and entered a nose-down descent before impacting terrain. A postcrash fire ensued. 

A video study determined that both engines continued to operate until impact and that their speeds ranged from approximately 1,978 rpm to 2,098 rpm, somewhat below the 2,200- to 2,300-rpm takeoff speed. 

The pilot had cardiovascular disease, including moderate coronary artery disease, an implanted pacemaker/defibrillator, and obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) device use. The FAA issued the pilot an Authorization for Special Issuance for a Second-Class medical certificate with permanent pacemaker implantation, atrial fibrillation, obstructive sleep apnea treated with CPAP and the use of medication

The pilot’s cardiovascular disease was associated with an increased risk of sudden impairment or incapacitating cardiovascular event such as ventricular arrhythmia, heart attack, or stroke. No forensic evidence indicated that such an event occurred. However, such events do not leave reliable autopsy evidence if the event occurs just before death, and no data were available from the pilot’s implanted pacemaker/defibrillator. Thus, the investigation was unable to determine if sudden incapacitation or impairment was a factor in this accident. 

Postaccident examination found no evidence of preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. Flight control continuity from the cockpit controls to the primary flight control surfaces was established; the observed flight control cable separations were consistent with damage sustained during the accident sequence.

The airplane flight manual specified that the flaps should be in the Up position for takeoff. However, witnesses observed the airplane taxi and takeoff with the flaps fully extended. One witness reported that the airplane appeared to be moving extremely slowly after liftoff and that, although the landing gear retracted, the flaps remained fully extended. At an altitude of about 200 to 300 ft agl, the airplane pitched up, and the witness observed the left wing drop before the airplane entered a nose-down descent. The video study showed that the airplane flew approximately straight until about 4.7 seconds before impact, when it began a left turn, and that it impacted terrain in an approximately 90 left-wing-down attitude. The observed pitch increase, left-wing drop, and subsequent nose-low descent were consistent with the airplane exceeding its critical angle of attack and entering an aerodynamic stall at an altitude insufficient for recovery. 

- Probable Cause: The pilot’s exceedance of the airplane’s critical angle of attack during the initial climb, which resulted in an aerodynamic stall at an altitude insufficient for recovery. Contributing to the accident was the pilot’s failure to ensure that the airplane was properly configured for takeoff.

Aerodynamic stall/spin: Piper PA-28R-180 Cherokee Arrow, N3757T, fatal accident occurred on September 8, 2024, at Basin Harbor Airport (B06), Vergennes, Vermont

• Location: Vergennes, Vermont
• Accident Number: ERA24FA371
• Date & Time: September 8, 2024, 12:25 Local
• Registration: N3757T
• Aircraft: Piper PA28R
• Aircraft Damage: Substantial
• Defining Event: Aerodynamic stall/spin
• Injuries: 4 Fatal
• Flight Conducted Under: Part 91: General aviation - Instructional

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/195076/pdf

https://data.ntsb.gov/Docket?ProjectID=195076

On September 8, 2024, at 1225 eastern daylight time, a Piper PA-28R-180 airplane, N3757T, was substantially damaged when it was involved in an accident near Vergennes, Vermont. The non-certificated student pilot, flight instructor, and two passengers were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.

The flight instructor and owner of the airplane had been providing flight instruction to the noncertificated student pilot, who was not yet old enough to obtain a student pilot certificate. Earlier on the day of the accident, the airplane was flown from its home airport to an airport with a grass runway that was about 155 nautical miles away. About 2 hours after the airplane arrived at that airport, a witness observed the airplane as it was departing and recorded a video of its initial takeoff roll from the grass runway. Neither the witness nor the video observed the airplane’s liftoff or the accident. The airplane was later found at the accident site, which was located in a wooded area adjacent to the runway.

The airplane was equipped with brake controls only in the left front seat position, where the non-certificated student pilot was seated, so it is likely that the non-certificated student pilot controlled the airplane during at least some portion of the taxi, as it would have been difficult to maneuver the airplane on the ground without differential braking. Because the flight instructor’s logbook indicated that he had been providing instruction to the non-certificated student pilot, it is possible that she also manipulated the flight controls during the accident takeoff. Regardless, the flight instructor was the only certificated pilot aboard the airplane with access to the flight controls, and was responsible for ensuring the airplane remained under positive control. He was also responsible for intervening as necessary to maintain the safe operation of the airplane. Since the airplane was not equipped with brake controls for the front right seat occupant, if an emergency arose during takeoff that required the takeoff to be aborted, the flight instructor would not have the ability to stop the airplane using conventional braking. The only braking option for the flight instructor would be the use of the parking brake. However, there was no evidence that the accident sequence involved an attempted rejected takeoff.

Postaccident examination of the accident site and wreckage revealed that the airplane impacted terrain in a left-wing-low, nose-low attitude, consistent with an aerodynamic stall at low altitude. The main landing gear remained extended, and the landing gear control switch was in the extended position, consistent with the accident occurring shortly after takeoff. Examination of the engine revealed that the fuel injector servo throttle stop was missing the plastic material that surrounded the stop pin, which allowed the throttle to move slightly past the normal full throttle stop. The fuel injector servo was tested on a production test bench at an overhaul facility and the servo operated normally. The slight movement of the throttle past the normal full throttle stop likely did not result in a loss of power. Overall, no evidence of any mechanical malfunctions or failures of the engine were found that would have precluded normal operation.

A sound spectrum analysis of the witness video indicated that, at the beginning of the takeoff roll, the propeller was rotating at approximately 2,500 rpm. The airplane was equipped with a constant-speed propeller with a maximum governed speed of 2,700 rpm. The observed propeller speed, approximately 200 rpm below the maximum governed speed, could have been consistent with several possibilities, including the propeller governor setting, reduced engine power, or an improperly positioned propeller control. However, since the video ended early in the takeoff roll, it could not be determined whether the engine’s rpm increased further along the takeoff roll. The airplane’s tachometer was impact damaged; therefore, its accuracy could not be verified. The airplane was equipped with a digital engine monitor that recorded limited engine parameters such as the exhaust gas temperatures (EGT) and cylinder head temperatures (CHT). The last recording revealed that, at the time when recording stopped, the EGTs were at levels consistent with high engine power; though, the engine rpm and manifold pressure could not be precisely calculated. The EGTs were compared to the previous flight that day, and were comparable to those recorded during that flight. Although the available evidence did not allow the engine rpm to be determined throughout the takeoff roll, the engine monitor data provided no evidence of a loss of engine power or other mechanical malfunction that would have precluded normal engine operation.

Postaccident examination of the airframe revealed that the alternate air door was in the open position. The alternate air door was intended for use when the air filter or inlet was suspected of being clogged with debris or ice. The airplane’s alternate air door was installed in a location that would bring in unfiltered, warm air from inside the engine cowling, which typically resulted in a slight reduction in engine performance because of the lower density of the warmer air. Because the air filter was not found obstructed during the postaccident examination of the airplane, and icing conditions were not present, it is possible that the flight instructor inadvertently left the alternate air on following an operational check. According to the airplane’s Owner’s Handbook, the alternate air door should be closed for takeoff. Further examination of the airplane’s configuration revealed that the flaps were in the retracted position, which was confirmed by the witness video. The airplane’s Owner’s Handbook recommended a flap setting of 25° for takeoffs from soft fields (like the grass runway the airplane was departing from) to improve takeoff performance. Additionally, the elevator trim was found set for a slightly nose-down attitude, despite the handbook’s recommendation to trim for takeoff so that only very light back pressure on the wheel was required to lift the airplane. 

Two weight-and-balance calculations were performed. One assumed the airplane departed the home airport with full fuel, and the other assumed it departed fueled to an intermediate position. The calculation for full fuel at the home airport revealed that the airplane was within the maximum weight limitations; however, the center of gravity (CG) was forward of the forward-most CG limit. The calculation for the airplane being filled to the intermediate position revealed that it was still within the maximum weight limitations and was just within the forward CG limit. A forward CG can increase the back-elevator pressure and elevator control forces required to control an airplane’s pitch, and can result in a higher stall speed. 

The airplane’s configuration, including the alternate air in the open position, the flaps retracted rather than being in the 25° setting recommended for takeoffs from a soft surface, and a slight nose-down trim setting, was not consistent with the Owner’s Handbook recommendations for optimizing takeoff performance. Collectively, these configuration discrepancies likely reduced the airplane’s takeoff performance and indicate that the flight instructor had not ensured that the airplane was properly configured before takeoff. Additionally, the airplane’s likely forwardbiased CG would have resulted in a higher stall speed, and increased the risk of an aerodynamic stall. Coupled with the reduced takeoff performance as a result of the airplane’s mis-configuration, it is likely that the flight instructor lost control of the airplane during the initial climb after the airplane encountered an aerodynamic stall, resulting in an uncontrolled descent at an altitude too low to recover. 

- Probable Cause: The flight instructor’s failure to maintain control of the airplane, which resulted in the airplane exceeding its critical angle of attack and entering an aerodynamic stall. Contributing to the accident was the flight instructor's failure to properly configure the airplane for takeoff from a soft surface, which reduced the airplane’s takeoff performance.