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Aviation spatial orientation in relationship to head position and attitude interpretation

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Conventional wisdom describing aviation spatial awareness assumes that pilots view a moving horizon through the windscreen. This assumption presupposes head alignment with the cockpit "Z" axis during both visual (VMC) and instrument (IMC) maneuvers. Even though this visual paradigm is widely accepted, its accuracy has not been verified. The purpose of this research was to determine if a visually induced neck reflex causes pilots to align their heads toward the horizon, rather than the cockpit vertical axis. Based on literature describing reflexive head orientation in terrestrial environments it was hypothesized that during simulated VMC aircraft maneuvers, pilots would align their heads toward the horizon. Some 14 military pilots completed two simulated flights in a stationary dome simulator. The flight profile consisted of five separate tasks, four of which evaluated head tilt during exposure to unique visual conditions and one examined occurrences of disorientation during unusual attitude recovery. During simulated visual flight maneuvers, pilots tilted their heads toward the horizon (p < 0.0001). Under IMC, pilots maintained head alignment with the vertical axis of the aircraft. During VMC maneuvers pilots reflexively tilt their heads toward the horizon, away from the Gz axis of the cockpit. Presumably, this behavior stabilizes the retinal image of the horizon (1 degree visual-spatial cue), against which peripheral images of the cockpit (2 degrees visual-spatial cue) appear to move. Spatial disorientation, airsickness, and control reversal error may be related to shifts in visual-vestibular sensory alignment during visual transitions between VMC (head tilt) and IMC (Gz head stabilized) conditions.
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... In contrast, when pilots see real-world visual cues, they interpret their aircraft orientation by determining the position of their aircraft against a fixed horizon, thus using a world-referenced system (Gillingham and Wolfe, 1985;Grether, 1947;Roscoe, 1992). The previous statement is supported by a documented head-tilt phenomena studied originally by Hasbrook and Rasmussen (1973) and later by Patterson (1995). Both studies showed that pilots were subconsciously aligning their heads with the horizon. ...
... Both studies showed that pilots were subconsciously aligning their heads with the horizon. Patterson hypothesized that pilots were trying to maintain a clear retinal image of the horizon while the aircraft maneuvered, and were using the horizon as their primary visual cue for determining orientation (Patterson, 1995). He termed this head-tilt response the opto-kinetic cervical reflex (OKCR). ...
... Therefore, when a real-world feature is not visible, pilots can infer the location of the real-world feature by relying on the location of the symbology representing it. Since previous simulation studies have shown that pilots exhibit the OKCR in VMC (Braithwaite, Beal, Alvarez, Jones, and Estrada, 1998;Gallimore, Brannon, Patterson, and Nalepka, 1999;Gallimore, Patterson, Brannon, and Nalepka, 2000;Patterson, 1995;Smith, Cacioppo, and Hinman, 1997), one could hypothesize that the OKCR will be present when pilots are flying in VMC with the conformal horizon of the HMD symbology visible at the same time as the true horizon. Additionally, if the OKCR is observed with the HMD symbology in VMC, one could hypothesize that the OKCR will also be present with just the HMD symbology in IMC because of the conformal horizon symbol. ...
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Research has shown that spatial disorientation often occurs when pilots transition between real-world visual cues and head-down attitude instruments. Recent studies investigating the opto-kinetic cervical reflex (OKCR) indicate that when pilots transition between these two types of visual cues, they are also transitioning between frames of reference. Limited research has been conducted investigating pilots' response during transitions between real-world visual cues and helmet-mounted display (HMD) attitude symbology. Eleven pilots performed vertical "S" maneuvers in and out of clouds to simulate frequent transitions between visual meteorological conditions and instrument meteorological conditions using both primary flight symbology on an HMD and traditional head-down primary flight instruments. Because pilots focused primarily on the symbology during the task, the OKCR was not found. Results also revealed that pilots were better able to maintain commanded vertical velocity when using the HMD compared to the head-down instruments, which is attributed to the head-up location of the symbology. Having the HMD symbology superimposed on the real-world visual scene can provide additional visual cues that pilots can use to perform their task more efficiently.
... Accordingly, it has been suggested that a display-triggered OKCR in low visibility would improve, or be a precursor of improved, spatial awareness and SO (e.g. Patterson, Cacioppo, Gallimore, Hinman, & Nalepka, 1997). Gibson's optical invariants refer to the higher-order variables in the optic array that inform about properties of the environment (Gibson, 1979). ...
... Transitioning between the reference frames of the outside world and the aircraft framed instruments and displays may therefore lead to orientation conflicts causing SD (e.g. Liggett, 2003;Patterson et al., 1997). Consequently, in this regard, it may not be relevant to any great degree whether instruments and displays are of inside-out, outside-in, or hybrid approaches if they employ only the focal visual mode. ...
... The rotational x measure may be seen as a parallel to the OKCR observed during flight (Patterson et al., 1997). 30 Whereas the OKCR expresses itself as a lateral tilt of the head during aircraft rolls in VMC, the head maintains alignment with the vertical axis of the aircraft in IMC. ...
... In fact, SD is mentioned as the underlying contributing aeromedical factor in fatal aviation mishaps [1,5]. If not quickly recognized and resolved, SD can lead to incor-rect control inputs, resulting in an entry into unusual attitudes, a loss of control in-flight or controlled flight into terrain [6]. While SD mishaps are usually fatal, their share in all accidents ranges 2.5-30.8% in different aircraft types [1,2]. ...
... Many studies [6,25] indicate that, during their entire careers, pilots can experience an SD incidence in the range of 90-100%. This is also confirmed by the results of this study, in which 96% of the surveyed pilots reported that they had experienced ≥1 in-flight SD illusion. ...
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Objectives: The study aimed to establish the current incidence and severity of spatial disorientation (SD) in Polish military pilots when flying different aircraft types over their entire careers, and to determine how SD training and pilots' flight experience might benefit their recognition of situations that may cause SD. Material and Methods: Overall, 176 military Polish pilots (aged 33.8±7.72 years, the number of flying hours: 1194±941) flying different aircraft types, who attended the aviation medicine course, were surveyed and asked to report their episodes of SD. To collect anonymous data, a postal SD questionnaire (INFO PUB 61/117/5) was used. Results: In the overall incidence rate of SD (96%), the most commonly experienced SD illusion was "loss of horizon due to atmospheric conditions" (81%). More SD incidents were reported by pilots who had received SD training. Some differences in the categories of the most commonly experienced SD illusion episodes between aircraft types were found. A severe episode adversely affecting flight safety was categorized by 10% of the respondents. Conclusions: In Polish military aviation, episodes of SD are a significant threat to aviation safety. There is evidence for the beneficial effects of SD training in the improvement of pilots' ability to recognize those factors that lead to SD.
... R6) would allow the user simultaneously to control different parts of the body relative to the distal teleoperation environment and the local gravito-inertial environment (cf. Patterson et al. 1997; Smith et al. 1997). Are people in moving rooms, patrons of the cinema, and users of virtual reality devices really fooled? ...
... In the target article we argued for the independence of different physical referents for motion, and we proposed that different aspects of behavior might be perceived and controlled simultaneously, relative to different physical referents . Recent research has demonstrated simultaneous differential control of the head and body with respect to independent , referents (Patterson et al. 1997; Smith et al. 1997). During simulated visual flight maneuvers (i.e., turns when the aircraft was controlled by looking out the win-dows), pilots tilted their heads (relative to the torso), so that the head remained aligned with the horizon, while simultaneously they controlled the torso so that it remained aligned with the aircraft as the latter rotated relative to the horizon. ...
... R6) would allow the user simultaneously to control different parts of the body relative to the distal teleoperation environment and the local gravito-inertial environment (cf. Patterson et al. 1997;Smith et al. 1997). Are people in moving rooms, patrons of the cinema, and users of virtual reality devices really fooled? ...
... In the target article we argued for the independence of different physical referents for motion, and we proposed that different aspects of behavior might be perceived and controlled simultaneously, relative to different physical referents. Recent research has demonstrated simultaneous differential control of the head and body with respect to independent, referents (Patterson et al. 1997;Smith et al. 1997). During simulated visual flight maneuvers (i.e., turns when the aircraft was controlled by looking out the win-dows), pilots tilted their heads (relative to the torso), so that the head remained aligned with the horizon, while simultaneously they controlled the torso so that it remained aligned with the aircraft as the latter rotated relative to the horizon. ...
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... Une Anastasopoulos et al., 1997 ; Bisdorff et al., 1996 ; Bronstein, 1999 ; Darling et Hondzinski, 1997 ; Ito et Gresty, 1996, Mast et Jarchow, 1996, Mittlestaedt, 1995). Le modèle de van Beuzekom et van Gisbergen (2000 ; Le vol en formation (Fig. 23) Braithwaite et al., 1998a ; Merryman et Cacioppo, 1997 ; Patterson et al., 1997 ; Smith et al., 1997). ...
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