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Airline transport operations are carried out in a wide range of visual and instrument meteorological conditions. For all but the most limiting of degraded visibility situations, the pilot can choose to fly the approach to the airfield and land the aircraft manually. S/he does this using the visual cues available through the cockpit windshield. The answer to the question - how is this achieved may seem rather obvious, but has actually challenged researchers for some time. The optical flow theory of visual perception offers solutions in terms of the way pilots pick up motion from the environment in which they move. In a relatively recent incarnation, flow theory transforms motion into the temporal, time-to-contact parameter, τ, defined as the time to close the motion gap to a surface or object at the instantaneous closure rate. This thesis reports on the development of novel display formats, using τ theory as a basis, for the fixed wing jet transport approach and landing manoeuvres. A simulation model of a generic large jet transport aircraft is constructed and a number of repeatable flight test manoeuvres developed. Using these as a start point, a number of flight test trials are conducted. The first two of these is to establish whether or not coherent τ-based relationships exist for a series of motion gaps identified for each flight test manoeuvre. Here, it is discovered that for the localiser capture, glide slope capture and flare manoeuvre, pilots use constant rate of change of τ (τ̇) guidance strategies to close the motion gaps of interest. The use of such strategies is consistent with the pilots coupling onto the τ-guides that τ theory postulates. This result is consistent with previous work conducted using rotary wing aircraft. Based upon the results obtained, a number of concept displays are developed. First, a two-dimensional lead aircraft concept is developed. Here, the pilot must overlay a prediction of the aircraft position at some near-future time with that of the desired position. Speed cueing is provided by the lead aircraft 'looming' if there is a difference between desired and actual airspeed. Second, a flare command display is developed. It provides a commanded flight path angle to achieve a desired τ̇ of height. Again, the pilot must overlay the actual aircraft flight path with desired. In order that these display designs could be finalised, the values of a number of parameters had to be established. A display development trial was conducted for this purpose. The specific values of interest and their final values were: optimum look-ahead time for a lead aircraft to guide the pilot along a given trajectory was found to be 2 seconds; for the localiser capture manoeuvre, the gap closure τ̇ was set at 0.6 and the gap closure duration fixed at 10 seconds; for the glide slope capture manoeuvre the gap closure τ̇ was also set at 0.6 and the duration at 5 seconds; for the flare command display, the τ̇ commanded was 0.75 and the initiation τ at 3.5 seconds. The novel display formats were tested by comparing them with a conventional head-down primary flight display, a 'state-of-the-art' head up display and a highway-in-the-sky concept. The comparison was performed using objective measurement of actual and desired trajectories and subjective measurement using the NASA display flyability rating scale and the Bedford workload scale. During this testing, the looming cue was found to be insufficient for the purposes of accurate speed control. However, the lead aircraft concept is shown to provide superior trajectory tracking over the alternative display formats in both good and degraded visual environments. The improved performance comes at the expense of slightly higher pilot-perceived workload. The τ-based flare command display is shown to provide landing touchdown performance as least as good as a current state-of-the-art head-up display in both good and degraded visual environments. Based upon the design process followed and the results obtained, a number of conclusions are drawn. The most important is that τ-based motion gap closure strategies are a fundamental means by which pilots guide aircraft through the environment. As such, the future display designers should incorporate the methods and approach discussed in this thesis.

Air defence decision making is demanding, time pressured and complex. Operators must make complex and cognitively demanding decisions in dynamic and uncertain environments. This thesis sought to increase the understanding of, and measure, decision confidence and accuracy in air defence decision making. In doing so, a novel method was designed and developed which was based on an integration of Classical Decision Making (CDM) and Naturalistic Decision Making (NDM) theories of decision making. Decision making is dependent on an interaction between both the situational demands of the task as well as individual differences in the decision maker. In addition, two key elements of decision making are the accuracy of the decision taken and its associated confidence. The body of work contained in this thesis, therefore, examined the impact of both external factors relating to decision making which included Decision Criticality, Task Load, Time Pressure and Audio communication, as well as the internal factors of Personality, Cognitive Constructs and Video Game experience. These factors were considered in relation to decision accuracy, confidence and W-S C-A (a measure of metacognitive ability). The experimental stimulus was developed with the help of Subject Matter Experts. This included the development of a realistic computer-generated air defence scenario in which the Task Load (high, moderate, low) was varied. In addition, an appropriate range of classifiable decision options, which varied in Decision Criticality (high, medium, low) was also generated. Three-hundred novice participants and twenty-two experts took part across a range of experiments. The Experimental Work consisted of two sections. The first section contained the foundation and investigatory work. The second section assessed the application of this measure through the use of feedback/training and expert participants. The results highlight the impact that Decision Criticality, which is the level of consequence associated with a decision, has on individual decision making. Findings show that a decision which was higher in criticality impacted positively on the performance by increasing decision accuracy. Individual participants tended to be less confident in their decisions when responding to decision events of medium criticality. Higher Decision Criticality was also shown to increase metacognitive abilities. That is, individuals were better able to discriminate between their accurate and inaccurate responses. Decision confidence was found to be both relatively stable and high across the experiments, indicating high levels of confidence in decisions, regardless of any other experimental variables including Task Load, Time Pressure and Audio. Such confidence was heightened in individuals who played video games on a regular basis. Internal factors also suggest that there may be individual differences that relate to decision making. Indeed, a higher tolerance of ambiguity may be beneficial in helping individuals deal with uncertain environments, such as in air defence. Although results of personality trait were largely inconclusive, low neuroticism and high conscientiousness appear to be beneficial in critical environments. Additionally, through the introduction of a metacognitive feedback training element, the research investigated the application of the measure. The results from this study demonstrated that, with metacognitive instruction, individuals displayed improved metacognitive ability. The experimental work also contains the first research to apply this method using active Royal Navy air defence personnel. The results from this experiment replicated the findings of criticality in the novice participants. The results thereby identify how this approach could be applied to air defence settings, and, illustrate the increased ecological validity of the findings. Recommendations suggest the findings can be applied to training and decision support technology. Further, the outcomes generally support the potential use of more traditional experimental methods alongside naturalistic approaches in critical environments, and that such an approach is warranted. Researchers and practitioners need to consider new approaches to research design to examine decision making in critical environments going forward. Overall, this thesis further contributes to the air defence decision making domain by providing valuable insights into the external and internal factors that are significant and relate to air defence decision making. Importantly, the work clearly showed Decision Criticality as an important factor that needs to be addressed when investigating decision making in critical environments. Individual differences were also demonstrated to be an important consideration.