The Nature of Procedural Interrupts in Ground Operations in Aerospace Systems

Abstract

This study proposes a methodology for characterizing the causal context and consequences of procedural interrupts in ground operations tasks. Behavioral science researchers observed 26 ground maintenance tasks at NASA's Kennedy Space Center. During the course of each task, there were periodic interruptions that required team members' attention and delayed task completion. From the tasks observed, 81 procedural interrupts were identified and coded for the following information: source of the interrupt, circumstances surrounding the interrupt, and consequences of the interrupt.We found that a greater number of interrupts were equipment or personnel-related while very few were procedure-related. More interrupts were due to unavailable resources or resources being incorrect than resources being inaccessible. The majority of interrupts resulted in planning or some action being taken. Variation in the duration of procedural interrupts was examined across causal categories. Interrupts that resulted in waiting took longer to resolve than those that involved planning or acting. Those interrupts related to personnel and equipment take longer to resolve, whereas interrupts related to procedures are remedied more quickly.The characterization process helps to identify procedural interrupts that cannot be avoided, those that are disruptive, and those that may be prevented through better planning or scheduling of resources. It is important to understand the nature of these interruptions and their associated delays in order to assess the overall impact on efficiency and safety. Further research involving the use of this methodology in conjunction with performance metrics is discussed.A single subject repeated measures design, replicated four times, was used to investigate the utility of stick control modulations to index pilot workload. Four subjects engaged in an aircraft-type workload simulation task. Our modification of the Multi-Attribute Task Battery consisted of a primary task (a video-game-like stick control task, wherein the goal is to place crosshairs over an evasive target aircraft symbol), and a secondary task, (accuracy/time-to-respond to out-of-normal range cues to gauges and warning lights). The subject simultaneously performed the primary and secondary task on even numbered game trials; on odd numbered trials only the primary task was performed. On a relative scale the first two games were slow, the next two were medium, and the last two were fast. The three levels of workload due to gamespeed and two levels due to primarylsecondary tasks comprised a sixgame set. A subject's data from twenty such sets were analyzed in a 3 * 2 factorial design. For each 30-sec. game the dependent measures consisted of a set of three workload criterion variables, including global subjective workload ratings, accuracy scores (a function of time on target), and tracking RMS error; a set of eight statistics on stick modulations, including mean amplitude, velocity, acceleration, frequency, as well as amplitude SD, velocity SD, amplitude...