Flight Deck Human Factors Issues in Vertical and Lateral Deviations during North Atlantic Flight Operations

This paper describes analyses of vertical and lateral deviations in the North Atlantic (NAT) Region. We focus on events attributed to unintentional pilot error. We studied NAT deviations since this region already uses some of the capabilities envisioned under Trajectory Based Operations (TBO), such as Controller-Pilot Datalink Communications (CPDLC) and half-degree waypoint coordinates for latitude and/or longitude. Half-degree waypoints could be used for dynamic routes under TBO; CPDLC may be used to communicate this information. Our analysis of vertical deviations focused on conditional clearances, which require pilots to begin and/or end altitude changes upon specific conditions (either in time or position). CPDLC messages that restrict both when an altitude change can begin and by when it must be completed are especially prone to error. We analyzed brief descriptions of events from the NAT from 2017, and from the New York Oceanic Control Area from 2014-2018. Our analysis finds that similar errors are still occurring, particularly in N ew York West Atlantic Route Systems (WATRS) airspace. Although controllers are issuing fewer such conditional clearances, when they are issued, they are still resulting in vertical deviations. Our analysis of lateral deviations focused on the use of half-degree waypoints without published names, and we also studied deviations in general. Unnamed half-degree waypoints can have ambiguous labels on flight deck displays, which might cause flightcrew errors. We examined 169 lateral deviations from 2017 and 68 events from 2018 to assess the magnitude of the issue and potential mitigations. We identified just six deviations with evidence of flightcrew issues related to waypoint display labels, three Gross Navigation Errors (GNEs), which are deviations greater than 10 NM, and three deviations under 10 NM. Together, these analyses validate the effective flightcrew strategies identified in guidance documents for NAT and global operations published by the International Civil Aviation Organization (ICAO). We offer additional human factors recommendations to mitigate risk, such as design changes for flight deck systems. We also discuss potential considerations related to TBO.