Spatial Disorientation and Vertigo in Aviation: A Review

Introduction

Vertigo is the false perception of motion and movement, which causes a person to experience confusion and disorientation. It is a condition that can be experienced by pilots—even veteran pilots—and the experience can result in crashes and fatalities. When this occurs, the investigations that follow typically refer to aviator or pilot vertigo as spatial disorientation (SD) (Gibb, Ercoline & Scharff, 2011). It can happen without warning, and it has been the cause of pilot fatalities spanning decades (Gibb, 2010). This literature review examines relevant peer-reviewed articles on this topic to assess what researchers have found, and what recommendations have been made to help address the issue of pilot vertigo.

The Prevalence of Vertigo in Aviation

Vertigo, or spatial disorientation (SD), is a phenomenon that occurs consistently in aviation. It has been found to cause a third of all aviation mishaps and carries a near-100% fatality rate when it occurs (Gibb et al., 2011). Yet, for all this, efforts to mitigate the risk of vertigo among pilots remain relatively lacking, despite the fact that it is cited as the cause of pilot crashes in one out of every three incidents (Gibb et al., 2011). As Webb, Estrada, and Kelley (2012) point out, SD has severe effects on cognitive processing, and even the most experienced pilots can make life-ending wrong decisions if they are suddenly affected by SD. That is why Gibb et al. (2011) recommend that pilots receive more training in recognizing the signs of vertigo and developing a greater respect for the condition.

The study by Gibb et al. (2011) is notable in that it examines more than 30 research studies along with 10 mishap case studies that demonstrate how critical it is to understand the issue of pilot vertigo. The study is well-researched and highlights several problems that prevent vertigo from being better addressed—among them, the fact that it is often underreported by pilots. There is also an inherent bias among active pilots who, when surveyed, believe that vertigo is not a real or serious problem they are likely to face (Holmes et al., 2003). However, while the survey by Holmes et al. (2003) does highlight pilot perceptions of the problem, the use of a self-reporting survey method calls its reliability and validity into question. Self-reported data can always be questioned with respect to underreporting and misrepresentation of a phenomenon. This is why the study by Gibb et al. (2011) carries greater validity: it draws on actual case studies and research articles spanning more than a century, all of them demonstrating the seriousness of pilot vertigo and its deadly consequences.

Gibb (2010) showed that SD rates are not decreasing and have remained consistent for decades, going back to the 1940s. Those findings served as part of the basis for subsequent research conducted by Lewkowicz, Francuz, Bałaj, and Augustynowicz (2015), which sought to assess oculomotor activity in various flying situations in which the risk of spatial disorientation might arise. Lewkowicz et al. (2015) conducted a controlled study with 20 pilots and 20 non-pilots at the Military Institute of Aviation Medicine (MIAM) in Warsaw. Participants completed a series of aircraft piloting tasks using the Gyro-IPT simulator. The researchers employed a mobile oculographic device to track participants' oculomotor activity and determine a false illusion profile. The findings were used to help develop an explanatory model of visual scanning processes in pilots that could be incorporated into software to help mitigate the risk of SD-related fatalities (Lewkowicz et al., 2015). The study's small sample size may limit its generalizability; however, the fact that it was conducted at all demonstrates that some efforts are being made to address the issue raised by Gibb (2010) and Gibb et al. (2011): pilot vertigo is a serious problem that demands attention.

Areas on Which Researchers Are Focusing

Current research on pilot vertigo is focusing on eye-tracking software that can help reduce the risk of pilot crashes. As in the study by Lewkowicz et al. (2015), the study by Balaj et al. (2019) examines the seriousness of SD and how a pilot's gaze behavior can be monitored to help a system detect when a pilot may be experiencing vertigo. Vertigo cues were described by Balaj et al. (2019) as affecting both pilot and non-pilot eye behavior in the same manner—which supports the argument advanced by Gibb et al. (2011) and Lewkowicz et al. (2015): SD is a phenomenon capable of causing even experienced pilots to freeze and behave as novices in the cockpit. It is therefore a serious issue that should be studied and addressed, notwithstanding the dismissal reported by surveyed pilots who claim never to have experienced it (Holmes et al., 2003).

The limitation of the Holmes et al. (2003) study is that its methodology does not support a valid conclusion. Self-reported data from participants does not overrule the evidence accumulated by scholars over the decades, nor does it nullify the new evidence produced by Balaj et al. (2019) regarding the effects of simulated pilot vertigo on eye behavior in the cockpit—whether the person involved is a trained, experienced pilot or not. The argument advanced by Balaj et al. (2019) is that the evidence shows that eye-tracking devices may be of assistance in addressing the issue of pilot vertigo, as eye behavior is consistent across participants who experience a simulated SD event.

Research conducted since 2000 has focused on eye behavior patterns as a potential focal point for addressing SD. The study by Cheung and Hofer (2003) did not set out specifically to test eye pattern behavior during SD-simulated events, but it noted that deviations in gaze behavior occurred during such events—particularly when the Coriolis vestibular cross-coupling-induced pitch illusion was applied to participants. When pitch illusion occurred in the simulation, participants were observed scanning the horizon differently than during normal flight conditions (Cheung & Hofer, 2003). This finding prompted other researchers to investigate eye pattern detection as a possible means of addressing pilot vertigo. Kowalczuk et al. (2016) built upon prior research by conducting a simulated flight test to examine specifically how vertigo affects pilots' vision. Their study, using 14 experienced pilots across three different tests, showed conclusively that eye pattern behavior is consistent during SD-induced events.

This finding is not entirely new: evidence of pilot eye behavior and gaze fixation deviations dates back to the Air Force Technical Report (No. 5967) by Fitts, Jones, and Milton (1949), whose findings were supported nearly half a century later by Bellenkes, Wickens, and Kramer (1997). Balaj et al. (2019) provide the most recent research on this topic through a controlled study using statistical analysis (ANOVA and MANOVA). The dependent variables identified in that study were pilots' deviation from in-flight performance indicators (i.e., heading, altitude, vertical velocity, and bank angle), the average duration of eye fixation, and the percentage of time pilots gazed at instruments. Balaj et al. (2019) used a sample of 40 participants—evenly divided between pilots and non-pilots, mirroring the sample size used by Lewkowicz et al. (2015)—and their findings confirmed those of the earlier study. Balaj et al. (2019) found that SD events can lead to a loss-of-control situation resulting in an unrecoverable deviation from the flight path during simulation. The Coriolis illusion was particularly noted as a problem for both pilots and non-pilots, confirming the findings of Cheung and Hofer (2003). One limitation noted in the Balaj et al. (2019) study, however, was that it did not account for pilot fatigue, which may arise after performing various maneuvers during simulation; accordingly, the researchers suggest that future studies control for pilot fatigue to confirm that the same SD events occur.

As Gibb et al. (2011) argue, the evidence collected by researchers from 2000 onward demonstrates that pilot vertigo is a serious issue in aviation requiring action. However, the problem of funding persists: no allocation from the U.S. Department of Defense budget has been designated for pilot vertigo research, despite the mounting evidence that it occurs and can be tracked through pilot eye movement. Gibb et al. (2011) note that other countries have provided funding for this type of research, as is evident in the Polish studies by Lewkowicz et al. (2015) and Kowalczuk et al. (2016). In the U.S., some studies have examined other factors that might contribute to pilot vertigo, such as the study by Long and Charles (2018), which investigated the effect of jet fuel fume exposure on cognition and delayed vertigo symptoms. Their study found that exposure of the external ear canal to jet fuel chemicals produced vertigo symptoms among both military and civilian personnel—indicating that an occupational hazard exists within the aerospace industry, and that the experience of vertigo implicated in a third of all plane crashes over recent decades is a pressing issue requiring further understanding (Gibb et al., 2011; Long & Charles, 2018).

Conclusion

Vertigo, or spatial disorientation, is a historical problem that has been well documented for decades (Gibb, 2010). Researchers have shown that pilot vertigo is responsible for a third of all crashes and that its seriousness is underscored by its near-100% fatality rate (Gibb et al., 2011). Yet, in the U.S., adequate funding has not been allocated to further research or to the development of a cognitive tool capable of detecting vertigo signs in pilots by monitoring eye pattern behavior and intervening before a loss-of-control situation occurs. European researchers have consistently shown that loss-of-control situations do arise among experienced pilots in vertigo-inducing simulations, particularly when the Coriolis illusion is involved (Kowalczuk et al., 2016). Polish researchers have been especially active in demonstrating that eye pattern behavior is consistent across both pilots and non-pilots when an SD event occurs in the cockpit (Balaj et al., 2019).

Although additional contributing factors—such as pilot fatigue or exposure to jet fuel chemicals—may play a role in the problem (Balaj et al., 2019; Long & Charles, 2018), the argument of Gibb et al. (2011) remains compelling in the U.S. context: insufficient attention has been given in American research to the problem of vertigo within the aviation industry. Nevertheless, recent research has shown that in civilian aviation, software tools already exist to monitor pilot eye pattern behavior (Chee et al., 2021). The continued development of these tools to prevent vertigo-induced crashes should remain a priority for researchers and policymakers alike (Chee et al., 2021).

References

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Bellenkes, A. H., Wickens, C. D., & Kramer, A. F. (1997). Visual scanning and pilot expertise: The role of attentional flexibility and mental model development. Aviation, Space, and Environmental Medicine, 68, 569–579.

Chee, S. M., Bigornia, V. E., & Logsdon, D. L. (2021). The application of a computerized cognitive screening tool in naval aviators. Military Medicine, 186(Supplement_1), 198–204.

Cheung, B., & Hofer, K. (2003). Eye tracking, point of gaze, and performance degradation during disorientation. Aviation, Space, and Environmental Medicine, 74(1), 11–20.

Fitts, P. M., Jones, R. E., & Milton, J. L. (1949). Eye fixations of aircraft pilots. III. Frequency, duration, and sequence fixations when flying Air Force ground-controlled approach system (GCA). Air Materiel Command Wright-Patterson AFB OH.

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Holmes, S. R., Bunting, A., Brown, D. L., Hiatt, K. L., Braithwaite, M. G., & Harrigan, M. J. (2003). Survey of spatial disorientation in military pilots and navigators. Aviation, Space, and Environmental Medicine, 74(9), 957–965.

Kowalczuk, K. P., Gazdzinski, S. P., Janewicz, M., Gąsik, M., Lewkowicz, R., & Wylegó, M. (2016). Hypoxia and Coriolis illusion in pilots during simulated flight. Aerospace Medicine and Human Performance, 87(2), 108–113.

Lewkowicz, R., Francuz, P., Bałaj, B., & Augustynowicz, P. (2015). Flights with the risk of spatial disorientation in the measurements of oculomotor activity of pilots. The Polish Journal of Aviation Medicine and Psychology, 21(3), 23.

Long, R. J., & Charles, R. A. (2018). Aviation fuel exposure resulting in otitis externa with vertigo. Aerospace Medicine and Human Performance, 89(7), 661–663.

Webb, C. M., Estrada, A., III, & Kelley, A. M. (2012). The effects of spatial disorientation on cognitive processing. The International Journal of Aviation Psychology, 22(3), 224–241.