GM5 CS FTL.1.205(a)(2) Flight duty period (FDP)

APPROPRIATE FATIGUE RISK MANAGEMENT (APPROPRIATE FRM) — THE PRIOR SLEEP WAKE MODEL

(a)The Prior Sleep Wake model (PSWM) is a simple method that may be used among other methods to predict the likelihood of accumulating fatigue or sleep debt and to assess crew fitness for duty, based on scientific evidence and principles. Most evidence suggests that to maintain optimum performance, health, and well-being, individuals should get between 7 and 9 hours of sleep during a 24-hour period. Many studies have investigated how decreasing levels of sleep and increasing time awake affects performance. In general, research has found that performance begins to become impaired after getting less than 5 hours of sleep over a 24-hour period. Performance also becomes impaired if sleep consistently falls below 6 hours per night on an ongoing basis. Sleepiness is related to factors such as the time of day, the time since awakening and the duration of prior sleep. As prior sleep decreases and time awake increases, the likelihood of fatigue-related symptoms, errors, and incidents also increases. The PSWM allows the operator to set minimum and maximum thresholds for sleep and time awake, according to the specific work risk profile of the crew members concerned, to determine whether they have obtained sufficient sleep and are by inference fit for duty. These thresholds should not be treated as targets. The PSWM also allows crew members to calculate for themselves how much sleep they have had and how long it has been since their last sleep period. The operator may decide that crew members, after assessing their own fitness for duty, report to their supervisor when they do not meet the relevant thresholds. This simple and practical process can flag sleepiness and fatigue before they lead to a safety issue. When crew members report to a supervisor that they have had insufficient sleep, it is important that clear procedures be in place to manage the risk in a consistent manner. The PSWM has limitations which operators and crew members need to be aware of. The model does not account for crew circadian rhythm, workload and sleep quality, to name a few. Therefore, where used, the PSWM may be one element of the appropriate FRM, but not the only element. Operators and crew members may use complementary methods and tools to validate predictions about fatigue made by the PSWM or alternative methods and tools having similar characteristics.

(b)The prior sleep–wake score is calculated by means of the following table:

(*) Sleep in prior 24 (48) hours means the sleep duration in the 24 (48) hours prior to the start of a rostered duty period. Sleep in this context is a sleep period during a continuous, uninterrupted and defined rest period, following a duty or prior to a duty, during which a crew member is free of all duties, standby and reserve. It excludes in-flight rest and controlled rest. (**) Predicted hours awake refer to the period from wake-up from the last sleep period to the end of the rostered duty period.

(c)Fitness for duty is assessed by means of the following table: