This paper reports on small-scale experiments conducted with air traffic controllers. The objective was to investigate non-nominal situations when using airborne spacing in the terminal area. The following situations were considered: mixed equipage, holding patterns and typical unexpected events (go-around, emergency, radio failure, spacing instructions not correctly executed). In applying the airborne spacing procedure for non equipped aircraft, handling mixed equipage was found to be entirely feasible. Initial trends suggest that 50% equipped aircraft already brings some benefits compared to 0% although not as much as with 100%. Receiving aircraft from the holding patterns and then using airborne spacing for final integration was found feasible and comfortable. Recovering from the unexpected events was found less difficult than initially anticipated and was evaluated as similar to today’s operations.
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