Aircrew rostering workload patterns and associated fatigue and sleepiness scores in short/medium haul flights under RBAC 117 rules in Brazil

TL;DR

This study analyzes how workload patterns in Brazilian short/medium haul flights under RBAC 117 influence aircrew fatigue and sleepiness, using questionnaires, workload metrics, and fatigue models to identify risk factors and mitigation strategies.

Contribution

It introduces a linear relationship method to estimate fatigue and sleepiness from workload metrics over a 168-hour period, validated with Brazilian aircrew data.

Findings

Workload metrics correlate with fatigue and sleepiness scores.

Mitigation strategies reduce high fatigue and sleepiness scores.

KSS scores align with pilot error risk levels.

Abstract

The relationships between workload and fatigue or sleepiness are investigated through the analysis of rosters and responses to questionnaires from Brazilian aircrews, taken from Fadig\^ometro database. The approach includes temporal markers - coinciding with Samn-Perelli (SP) and Karolinska Sleepiness Scale (KSS) responses - where SAFTE-FAST model outcomes are calculated. The model results follow the increase of fatigue and sleepiness perceptions during the dawn (0h00 to 05h59), but underestimate the self-rated scores during the evening (18h00 to 23h59). On the other hand, the KSS scores fit the relative risk of pilot errors, representing a reasonable proxy for risk assessment. Linear relationships obtained between workload metrics, computed within 168-hours prior to the responses, and self-rated SP and KSS scores provide a consistent method to estimate accumulated fatigue and sleepiness. Considering 7149 rosters of 2023, the duty time ($DT$), the number of flight sectors ($N_{CREW}$) and the sum of flight sectors with sit periods longer than one hour ($N_{CREW}+N_{SIT}$) are associated with 70.1%/60.6% of the highest predicted scores of SP/KSS. Applying the mitigations $DT\leq44h$, $N_{CREW}\leq15$ and $N_{CREW}+N_{SIT}\leq19$ for every 168-hour interval yields a significant decrease in the higher values of SP/KSS with minimal impact on aircrew productivity.