Loss of Control (LOC) accidents are a major threat for aviation, and contribute the highest risk for fatalities in all aviation accidents. The major contributor to LOC accidents is pilot spatial disorientation (SD), which accounts for roughly 32% of all LOC accidents. A pilot experiences SD during flight when the pilot's expectation of the aircraft's state deviates from reality. This deviation results from a number of underlying mechanisms, such as distraction, failure to monitor flight instruments, and vestibular illusions. Previous researchers have developed computational models to understand those mechanisms. However, these models are limited in scope as they do not model the pilot's knowledge of the aircraft dynamics. This research proposes a novel model to predict the best-possible-pilot-expectation of the aircraft state given vestibular and visual cues. The proposed model uses a Model-Based Observer (MBO) as the infrastructure needed to establish an “expert pilot”. Expert pilots are known to form an internal model of the operated system through training and experience, which allows the expert to generate better internal expectations of the system states. Pilots' internal expectations are enhanced by the presence of information fed through the pilots̕ sensory systems. Thus, the proposed model integrates pilot's knowledge of the system dynamics (i.e. an aircraft model) with a continuous vestibular sensory model and a discrete visual-sampling sensory model. The computational model serves to investigate the underlying mechanisms of SD during flight and provide a quantitative analysis tool to support flight deck and countermeasure designs.

<p>The problem of spatial disorientation during flight of aircraft is briefly described, as are definitions of the phenomenon. Traditional countermeasure efforts that are often directed towards changes in the central visual field are reconsidered in favour of presentation of information in the peripheral visual field. It is proposed to use optic flow to support spatial orientation, as well as to omit such information from the central visual field. An experiment was conducted, and results showed that forward visual flow gave very important spatial information. The flow could be cropped to a certain degree in the periphery (horizontally), as well as parts of the central presentation could be omitted without decreasing effects in the experiment. Implications relevant to possible implementations in aircraft are discussed.</p>

This thesis demonstrates how a model-based observer can be applied to estimate the reference pilot expectation that can be achieved with any instrument scanning behavior and established models of vestibular inputs. The MBO, developed by the Georgia Tech Cognitive Engineering Center, is applied here in both simple maneuvers examining spatial disorientation and full Air Traffic Control concepts of operations examining loss of energy state awareness. The computational experiments presented in this thesis examine how different effects (i.e., instrument scan pattern, accuracy of pilot perception of flight display information, and awareness of control surface deflections) can prevent or mitigate the susceptibility to spatial disorientation and loss of energy state awareness, thus setting requirements for intervention and countermeasure designs in terms of the scanning behavior they must foster.

The problem of spatial disorientation during flight of aircraft is briefly described, as are definitions of the phenomenon. Traditional countermeasure efforts that are often directed towards changes in the central visual field are reconsidered in favour of presentation of information in the peripheral visual field. It is proposed to use optic flow to support spatial orientation, as well as to omit such information from the central visual field. An experiment was conducted, and results showed that forward visual flow gave very important spatial information. The flow could be cropped to a certain degree in the periphery (horizontally), as well as parts of the central presentation could be omitted without decreasing effects in the experiment. Implications relevant to possible implementations in aircraft are discussed.

Pilot spatial disorientation (SD) is a significant cause of incidents and fatal accidents in aviation. The pilot is susceptible to SD especially in low visibility when the visual system is deprived of information from outside the cockpit. This thesis presents the notion of visual flow displays as enhancement of symbology on flight displays primarily in low visibility for improved support of the pilot’s spatial orientation (SO) and control actions. In Studies I and II, synthetic visual flow of forward ego-motion was presented on displays and postural responses were used as measures of display effectiveness in determining SO. The visual flow significantly affected SO, and although the increased stimulation of the visual periphery from a width of 45° to about 105° increased the effects there was no further effect at a width of about 150° (Studies I and II). Studies I and II also showed that omitting 20°- or 30°-wide central fields of view from the visual flow either reduced or not reduced the effects. Further, although inconclusive, Study II may indicate that horizon symbology in central visual field may enhance the effects of peripheral visual flow. The appropriate integration of peripheral visual flow with the head-up display symbology of the Gripen aircraft was presented. Acceleration in a human centrifuge was used in Study III to investigate the effects of synthetic visual flow on the primarily vestibular-dependent somatogravic illusion of pitch-up. Two experiments revealed a reduced illusion with the visual flow. The results of Experiment 2 showed the visual flow scene not only reduced the illusion compared with a darkness condition but also compared with the visual scene without visual flow. Thus, similar to the main findings of Studies I and II, synthetic visual flow can significantly affect SO and supports the visually dependent SO system in an essential manner.