Fatigue Field Study in United States Helicopter Air Ambulance Pilots: Methodology

Introduction: Helicopter air ambulance (HAA) pilots are exposed to fatigue risk due to on-call and shiftwork operations required for 24-hour emergency service. Cumulative fatigue, circadian disruptions, and sleep inertia may reduce safety margins, particularly in consecutive nighttime shifts and on-call emergency flights. Previous research on fatigue in HAA operations has largely focused on European operators, many of whom operate through state-run emergency service providers. HAA services in the United States (US) instead operate as private companies, with a variety of company policies and environments that could differentially affect pilot fatigue and sleepiness. The current field study aims to investigate how shiftwork and on-call demands in US HAA operations influence sleep, alertness, and performance across different schedule types.

Methods: All US HAA pilots working 7-days-on, 7-days-off schedules were invited to participate. Schedules of interest include daytime shifts (typically 0600–1800), nighttime shifts (typically 1800–0600), or mixed-shifts (e.g., 3 daytime shifts, followed by 4 nighttime shifts). Before data collection, participants complete a pre- study survey that includes demographic and operational questions, the Morningness-Eveningness Questionnaire, and the Epworth Sleepiness Scale. The data collection period includes 3 days pre- shift, 7 days on-shift, and 3 days post-shift. During this period, sleep is measured via wrist actigraphy and daily sleep logs. Pilots complete a 5-minute psychomotor vigilance test (PVT), Karolinska Sleepiness Scale (KSS), and Samn-Perelli (SP) fatigue scale three times per day. Following every flying operation, pilots complete an additional PVT, KSS, SP, and take the NASA Task Load Index.

Results: To date, 54 HAA pilots have consented to participate. This includes 21 pilots with daytime shifts, 19 pilots with nighttime shifts, and 14 pilots with mixed-shifts. These pilots represent 19 companies. So far, 19 participants have contributed 247 days of data, including 763 PVTs. Preliminary results are forthcoming.

Conclusion: Data collection for the study is ongoing. Participation so far suggests that the methodology is not overly burdensome to the pilots while on duty and that pilots are compliant with the study methodology. Additionally, the large spread of companies participating suggests that our recruitment strategy and advertising is successfully reaching a broad range of pilots. Support: This research is conducted under the Flight Deck Program Directive/Level of Effort Agreement between the Federal Aviation Administration NextGen Human Factors Division (ANG-C1) and the Aerospace Human Factors Research Division (AAM-500) of the Civil Aerospace Medical Institute.

Publication History

Article published online:
08 October 2025