Daher TBM 960 (N960LP) Crash, Potentially Caused by Somatogravic Illusion at Truckee-Tahoe Airport (TRK), California

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On March 30, 2024 at 6:37pm, a Daher TBM 960 aircraft (N960LP) was involved in an accident near Truckee, California while attempting to perform a missed approach procedure. The personal flight, under Part 91 of the Federal Aviation Regulations, resulted in the deaths of both the pilot and the passenger. Departing from Centennial Airport in Denver, Colorado, the aircraft climbed to 30,000 feet and maintained a westerly course before beginning its descent over Lake Tahoe, heading towards Truckee-Tahoe Airport (TRK). The flight data indicated several critical mode changes in the aircraft's autopilot and navigation systems during the final approach, culminating in a crash in snow-covered terrain 3,200 feet north of the runway. Visibility was under 0.34 miles due to light snow, and the airport's Visual Approach Slope Indicator (VASI) lights were inoperative (NOTAM issued for runway 21), adding to the landing challenges.

The accident's causes are under investigation by NTSB, focusing on multiple factors including adverse weather conditions and technical difficulties. The low visibility and overcast ceiling at 900 feet significantly impaired the pilot's ability to land safely. The failure of the VASI lights and unsuccessful attempts to activate runway lights further complicated the situation. Final flight data revealed rapid altitude changes and autopilot mode adjustments, indicating potential confusion or control issues during the missed approach. This incident highlights the critical importance of operational equipment, thorough pre-flight checks, and robust weather preparedness to ensure flight safety.

Amelia™ offers a Flight Envelope for the aircraft and a Health Envelope for the pilot, effortlessly integrating as an unobtrusive add-on within the avionics system, requiring no modifications to existing equipment. After encountering poor weather due to snow that in addition to the Visual Approach Slope Indicator (VASI) lights being inoperative, the pilot was not able to see the runway and initiated a missed approach, which was followed by a climbing right turn where multiple changes to the aircraft’s Autopilot mode was made. Just before the accident, the Autopilot was turned off as the aircraft climbed to 6,850 ft while making a left turn at 148 knots. The last ADS-B signal indicated the airplane was at an altitude of about 280 ft above the ground and a speed of 170 knots.

This suggests that even when the airplane was in a descent left turn, conditions were present that produced a potential somatogravic illusion of ascending flight and resulted in spatial disorientation of the pilot. Amelia™ provides a novel 3D holographic interface to the Flight Envelope, an intuitive way to gauge aircraft’s altitude, pitch, roll and other flight envelope parameters. Even with the somatogravic illusion of ascending flight, Amelia™ Flight Envelope would have alerted the pilot about the altitude, pitch and the roll angle being outside the flight envelope for that phase of the flight. This would have prevented the pilot’s spatial disorientation and the crash that followed.

Lesson Learned

While the investigation is ongoing, several key points are noted:

Importance of Operational Equipment: The failure of the Visual Approach Slope Indicator (VASI) lights and the challenges in activating runway lights likely contributed to the difficulty in landing. The pilot attempted to activate the runway lights approximately 2.4 nautical miles from the runway surface, but these efforts were unsuccessful. Ensuring that all navigational aids are operational, especially in poor weather conditions, is critical. Airports should have contingency plans and robust maintenance schedules to prevent such equipment failures, which can have severe consequences during landing.
Weather Preparedness: The adverse weather conditions significantly impacted visibility and possibly contributed to spatial disorientation or other pilot challenges. The METAR report indicated calm winds, visibility of 3/4 mile in light snow, and an overcast ceiling at 900 feet. The actual visibility was reported to be less than 0.34 statute miles at the time of the accident, highlighting the importance of pilots being prepared for rapid changes in weather. Comprehensive weather briefings and preparedness for such conditions can aid in making more informed decisions and managing unexpected situations.
Flight Data Monitoring: Detailed analysis of ADS-B data highlights the need for thorough pre-flight checks and understanding the aircraft's systems to manage unexpected situations during critical flight phases. The data revealed multiple critical mode changes in the aircraft's autopilot and navigation systems during the final approach. Pilots should be proficient in using these systems and prepared to handle manual operations if necessary. Regular training and simulations of emergency scenarios can enhance a pilot's ability to react appropriately under stress.

Flight Data Monitoring: Detailed analysis of ADS-B data highlights the need for thorough pre-flight checks and understanding the aircraft's systems to manage unexpected situations during critical flight phases. The data revealed multiple critical mode changes in the aircraft's autopilot and navigation systems during the final approach. Pilots should be proficient in using these systems and prepared to handle manual operations if necessary. Regular training and simulations of emergency scenarios can enhance a pilot's ability to react appropriately under stress.

2017 Cessna 182T Skylane, equipped with two multifunction displays (MFDs).

1978 Bellanca Citabria, a classic taildragger with analog controls

Consideration on User Experience in the Cockpit (Analog vs. Digital): From a product design perspective, simplicity and intuitive design can enhance user experience, making it easier for pilots to learn and operate the aircraft efficiently. Analog systems provide direct, physical interaction, which can be beneficial in high-stress situations. However, advanced digital features, like those in the TBM 960, must be designed to avoid overwhelming users. The series of autopilot mode changes during the final approach suggests a need for better interface design to support situational awareness and reduce cognitive load. Striking a balance between complexity and usability is crucial for enhancing safety. Read more: User Experience in the Cockpit: Analog vs. Digital

Human Limitations, Somatogravic Illusion: Somatogravic illusion is a false sensation of ascending or descending flight caused by acceleration or deceleration, often experienced in poor visibility conditions. After encountering poor weather conditions and inoperative VASI lights, the pilot was unable to see the runway and initiated a missed approach, followed by a climbing right turn. Multiple changes to the aircraft’s autopilot mode were made, and just before the accident, the autopilot was turned off as the aircraft climbed to 6,850 feet while making a left turn at 148 knots. The last ADS-B signal indicated the airplane was at an altitude of about 280 feet above the ground and a speed of 170 knots. This suggests that the pilot may have experienced a somatogravic illusion of ascending flight, resulting in spatial disorientation. To mitigate such risks, pilots should rely on their instruments rather than physical sensations, especially in poor visibility. Training to recognize and manage this illusion, along with using advanced systems like Amelia™ Flight Envelope, which provides a 3D holographic interface to gauge aircraft parameters, can help prevent disorientation and ensure safe flight operations.

Reference

NTSB Aviation Investigation Preliminary Report (WPR24FA119)

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