by Dr. Leo M. Hattrup, M.D., FAA Aeromedical Standards and Policy Branch
In this weather technology-themed issue, let’s look at a relevant topic all pilots must understand: spatial disorientation. Spatial disorientation, or "Spatial-D" occurs when a pilot cannot determine their position, location, and motion relative to their environment.
The General Aviation Joint Steering Committee (GAJSC), a joint industry/government organization, recently reviewed two weather related accidents. In each case, the pilot was instrument rated (but with uncertain proficiency) and the aircraft was equipped for instrument flight. The report does not identify any mechanical issues and neither pilot had a known medical deficiency. In both accidents, spatial disorientation was quite possible. All known circumstances also indicate that the pilots ignored basic tenets of ADM (aeronautical decision-making) and CRM (crew resource management).
The first accident involved a pilot who flew his Bonanza into an area of low instrument meteorological conditions (IMC). He made multiple 360s (looking for better weather?) and chose to scud run at less than 600 feet AGL. There is no record of an official or unofficial weather brief, nor did he contact ATC for assistance. The final event was probably an accelerated stall near the ground (the flight path was 45 degrees pitch down through the trees). These maneuvers suggest that he possibly experienced spatial disorientation resulting in the leans or a graveyard spiral.
The second accident involved a Cessna 340 pilot who actually had the aircraft towed to the takeoff runway. Why? He was concerned about hitting a parked aircraft or a hangar due to the reduced visibility. As the Cessna impacted the ground shortly after the departure end of the runway, the review team believes the pilot may have experienced the somatogravic illusion (a sensation of climbing due to acceleration).
The lack of CRM and ADM both clearly contributed to these accidents. It is easy to criticize and say “I would never do that.” But, is that accurate? For the most part, pilots are different from the general population. Many are so-called “Type A,” exhibiting both the determination and effort required to earn pilot certificates and ratings as well as the “I can handle it” confidence that can arise from successfully completing those important milestones (e.g., first solo, first instrument cross-country, etc.). Unfortunately, this same self-assurance can result in overconfidence and poor decision making. All of us are prone to continue a course of action once begun, even if the situation deteriorates from that expected. This tendency is termed “plan continuation bias.” Along with pressure to perform (e.g., if passengers are present), it can also impair the pilot’s ability to assess the actual risk of a situation and lead to disregarding important information such as cues suggesting spatial disorientation. In fact, a 2004 study by NASA determined that “plan continuation bias” was causal in 9 of the 19 air carrier accidents reviewed. The solution, of course, is to establish and adhere to personal limitations, ideally beginning with the preflight planning and continuing throughout the flight.
Nobody — but nobody — is immune to the impact of spatial disorientation. So please take the time to reacquaint yourself with spatial disorientation and human factors on a regular basis. Maintain instrument proficiency. Debrief your flights looking for areas to improve. Finally, determine your go/no-go points for all phases of flight early in the planning process.
Consider these resources:
Leo M. Hattrup, M.D., received a bachelor’s degree from Wichita State University, a master’s in public health from Harvard University, and a doctorate from Vanderbilt University. He is retired from the U.S. Air Force in which he spent the majority of his career in aerospace medicine. He is board certified in aerospace and occupational medicine. He is a certificated flight instructor and enjoys flying airplanes, helicopters, and gliders.