Equivalence Testing as a Tool for Fatigue Risk Management in Aviation

Area of Science:

• Occupational safety and health
• Aviation human factors
• Statistical methods in risk management

Background:

• Civilian aviation regulators increasingly favor evidence-based fatigue risk management over strict hours-of-service rules.
• Alternative methods of compliance require demonstrating safety levels "at least equivalent to" prescriptive regulations.
• Equivalence testing provides a framework for comparing fatigue and performance between different operational conditions.

Purpose of the Study:

• To discuss the application of equivalence testing in occupational fatigue risk management within aviation.
• To propose suggested margins of practical equivalence for key aviation safety performance indicators.
• To illustrate equivalence testing using a field study comparing pilot rest conditions.

Main Methods:

• A within-subjects field study involving 41 pilots on a long-range trip.
• Monitoring included actigraphy, sleep diaries, and psychomotor vigilance tasks (PVT).
• Pilots rested in either a standard lie-flat bunk or a tapered bunk on different flight sectors.

Main Results:

• Total in-flight sleep duration was equivalent between the standard and tapered bunk conditions (134 ± 53 min vs. 135 ± 55 min).
• Mean reaction speed on the PVT at top of descent was also equivalent (3.94 ± 0.58 vs. 3.77 ± 0.58).
• These results support the concept of practical equivalence between the tested rest scenarios.

Conclusions:

• Equivalence testing is a valuable statistical tool complementary to difference testing for assessing fatigue and performance.
• This method can be effectively applied in transportation policy decision-making for fatigue risk management.
• The findings support the use of equivalence testing to validate alternative operational strategies in aviation.