Measured Impact of an Interval Management Application During Revenue Operations

The Federal Aviation Administration’s (FAA) Automatic Dependent Surveillance – Broadcast (ADS-B) In Retrofit Spacing (AIRS) evaluation is demonstrating the operational feasibility and value of ADS-B In capabilities using a retrofit avionics solution. As part of this project, American Airlines has equipped their Airbus A321 fleet with avionics necessary to perform multiple applications. The Initial-Interval Management (I-IM) application allows controllers to instruct the flight crew of an equipped IM aircraft to achieve and then maintain an assigned spacing goal relative to a specified lead aircraft. Relative spacing from the lead aircraft is managed by implementing speed guidance on the IM aircraft. The relative spacing goal may be issued as a distance or time value to support time-based metering operations. The IM speed guidance onboard the IM aircraft yields more precise inter-aircraft spacing intervals than possible when speed instructions are issued by air traffic controllers, even when using decision support systems. The spacing precision possible from IM operations can lead to smaller inter-aircraft spacing intervals, on average, which yields throughput improvements at constrained resources (e.g., arrival meter fixes for managing aircraft flows into terminal airspace and arrival runways). Additionally, precise inter-aircraft spacing is expected to result in reduced controller vectoring, allowing flights to remain on their planned routes more frequently, leading to aircraft efficiency benefits. An I-IM evaluation began in November 2022 at Albuquerque Center (ZAB) and continued through November 2024. The paper presents analyses and results for I-IM. The results examine the IM spacing accuracy at meter points. Aircraft conducting time-based IM operations demonstrated an average interarrival time and standard deviation smaller than that available with current ground-based metering tools. Results were similar for distance-based IM operations.