Is ACARS and FANS-1A Just Another Data Link to the Controller?

This report investigates issues surrounding TBO procedures for the current aircraft fleet when requesting deviations around weather. Air and ground procedures were developed to stringently follow TBO principles using three types of communication: Voice, ACARS, and FANS. ACARS and FANS are both text-based communication systems, but FANS allows uplinked flight plans to be automatically loaded into the FMS, while ACARS does not. From the controller perspective, though, all flight plan modifications were completed using a trial planner and delivered via voice or data comm, making FANS and ACARS similar. The controller processed pilots’ request and approved or modified them based on traffic management constraints. In this context, the rate of non-conformance across all conditions was higher than anticipated, with off path errors being in excess of 20%. Controllers did not differentiate between the ACARS and FANS data comm, and showed mixed preferences for Voice vs data comm (ACARS and FANS).