Increasing Flexibility in the Design and Operation of Instrument Flight Procedures

Abstract

Instrument Flight Procedures determine aircraft departure and arrival trajectories in terminal airspaces. While their main objective is to ensure safe aircraft navigation, flight procedures also have a significant effect on the capacity, efficiency, access, and noise characteristics of airspaces by defining their route structure. The design of procedures is limited by a variety of constraints that restrict achievable aircraft trajectories. Many constraints originate from safety considerations and can interact in complex ways to limit flight procedure flexibility and system performance.

It is hypothesized that opportunities to increase system flexibility may exist through a better understanding of constraints and opportunities to reevaluate them based on technology improvements. Following a review of constraints and their effect on flexibility, the required geometric separation between flight procedures is identified as a significant constraint in the design of flight procedures and is chosen as the focus of an in-depth study to identify constraint reevaluation opportunities.

The collision risk between procedures is identified as the main driver of their required separation. Through an analysis of modern aircraft navigation performance in normal operations, it is found that the collision risk between procedures is expected to be dominated by the risk due to non-normal events (i.e., deviations), which can be controlled through the use of collision mitigation capabilities. As a result, it is posited that a better understanding of the collision risk between flight procedures under the effect of mitigations represents a key mechanism for identifying how technology improvements may enable the reevaluation of separation. To that end, a model of the mitigated collision risk between flight procedures is developed and presented.

In example applications of the proposed mitigated collision risk model, several potential system improvement paths are identified and discussed that could result in lower separation between procedures and therefore greater flexibility. These include improvements to mitigation technologies, better aircraft navigation reliability, and greater knowledge of aircraft non-normal behaviors that could lead to less conservative assumptions in collision risk modeling. Examples discussed in this thesis include the evaluation of the achievable separation between real procedures at Boston Logan Airport (BOS), which could offer noise benefits, and the evaluation of the achievable separation between future Advanced Air Mobility (AAM) routes. The methods presented in this thesis could be used to support the evaluation of future changes to separation as well as the planning of future mitigation systems.