ERA24LA227 · Brallier Scott GLASAIR I

The non-instrument rated pilot departed on a cross-country flight in dark night visual meteorological conditions (VMC). The flight was uneventful while over land, but flight track data showed that, after proceeding over the Gulf of Mexico, the airplane’s heading began to vary, and the airplane entered a slight right turn. The pilot was issued an air traffic control frequency change, which the pilot read back correctly, and shortly thereafter the airplane entered a left turn that continued more than 810°. The airplane then entered multiple heading changes followed by a steep descent, the pilot declared mayday, and the airplane impacted the water.

Another pilot flying in the area of the accident site around the time of the accident reported that it was “really really black” and “very hazy.” Review of weather information for the area of the accident site revealed few to broken clouds with bases around 4,000 ft and tops around 16,000 ft. The pilot did not obtain preflight weather information from Leidos Flight Service or ForeFlight, and the extent of his preflight planning could not be determined.

Postaccident examination of the flight controls for roll, pitch, and yaw, as well as the engine and its systems, including the engine-driven vacuum pump, revealed no evidence of preimpact failure or malfunction. Additionally, disassembly examination of the attitude indicator and electrically-operated turn coordinator revealed no evidence of preimpact failure or malfunction. A friend of the pilot reported that the airplane’s autopilot had recently been upgraded, but that the pilot was “having some problems with it.” The autopilot switch was found in the Off position, and the airplane’s heading and altitude changes observed in flight track data were consistent with the pilot hand-flying the airplane.

Autopsy of the pilot revealed evidence of cardiovascular disease, which was associated with some increased risk of an impairing or incapacitating cardiovascular event, such as heart attack or stroke. Although such an event cannot be excluded by autopsy evidence alone, there is no evidence that such an event occurred. While ethanol was detected at a very low level in cavity blood, it was not detected in vitreous fluid. This evidence indicates that some or all of the small amount of the detected ethanol may have been from postmortem sources rather than alcohol consumption, and that alcohol effects likely did not contribute to the accident.

The dark night conditions and the lack of available cultural lighting due to the airplane’s location over the water provided an environment conducive to the development of spatial disorientation. The pilot’s decision to embark on the flight into such conditions without an instrument rating and without the benefit of a fully functional autopilot increased his susceptibility to the effects of spatial disorientation. The airplane was established in a right bank at the time the pilot was issued a frequency change, and changing the frequency would have required him to divert his attention to the transceiver. Shortly thereafter, the airplane entered a left turn and eventually, a steep descent, which ended in impact with the water. The circumstances of the accident are consistent with the pilot experiencing the effects of the Coriolis illusion, which resulted in spatial disorientation and a loss of airplane control.

Verbatim NTSB analysis and probable cause from the NTSB dataset