Assessing FTL Effectiveness: Quantifying the Effect of Changes in Easa Regulations on Fatigue Risk and Crew Efficiency

Introduction: Flight and duty time limits (FTLs) for pilots and cabin crew, defined by regulators, establish clear scheduling boundaries for flight operators. While primarily designed to mitigate fatigue risk, these limits also significantly impact crew efficiency. This study aimed to develop a method for quantifying and optimizing the effectiveness of FTLs and to compare the impact of the previous (Subpart Q) and current (2016) EASA FTL regulations.

Methods: A large dataset of flight schedules was used where we included all scheduled passenger fleets operating more than 200 and 100 flights per week for narrow body and wide body operation respectively, during three typical calendar weeks. These planning problems were then used to generate crew rosters limited solely by regulatory boundaries, without additional operational constraints. These rosters were optimized using commercial industry-grade scheduling tools with a strive to maximize crew efficiency. The resulting rosters, which would be the realistic working patterns produced by new operators only governed by regulations, were then analyzed in terms of both crew efficiency and fatigue risk. The latter was estimated by using one of the leading bio-mathematical fatigue models within aviation and a well-established method for quantification translating sleepiness into risk for lapses/slips/mistakes/violations during critical phases of flight.

Results: The transition from Subpart Q to the current EASA FTLs, applied to European-based operations, led to: • Short-haul operations: A 3.2% increase in fatigue risk with a 0.6% decrease in crew efficiency. • Long-haul operations: A 7.8% reduction in fatigue risk, accompanied by a 7.0% drop in crew efficiency.

Conclusion: Mitigating and limiting fatigue risk through rigid (binary) rules presents challenges. The revised EASA FTLs reduced crew fatigue risk levels for long-haul operations, albeit at a substantial efficiency cost, while changes for short-haul operations were counterproductive. This study highlights the need for a more data-driven approach, and provides concrete examples thereof, when updating regulations to better balance fatigue risk and operational efficiency.

Publikationsverlauf

Artikel online veröffentlicht:
08. Oktober 2025