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To assess the benefits and limits of a new spacing instruction from flight crew perspectives, a pilot-in-the-loop experiment was conducted. Beyond assessing interface usability and overall feasibility, the experiments aimed at analysing the impact of various tolerance margins on flight crew activity and efficiency. Flight crew feedback was generally positive. Despite a new task in the cockpit, which requires appropriate assistance to contain workload, pilots highlighted the positive aspects of getting in the loop, understanding their situation (through goal-oriented instructions), and gaining anticipation. Results showed that even though the smallest tolerance margin (0.25NM) led to increased workload, the spacing deviation was usually below 0.5NM.
Hoffman et al. (2003) studied this question.