EASA report on FTL gives an overview of the work performed, results and recommendations, and critical assessment of the review of the effectiveness of the EU requirements concerning flight and duty time limitations and rest requirements.
A scientific study ranked duties by their impact on aircrew fatigue and focussed on the top-two ranked fatiguing duty types over 2 years.
The field study showed an increased probability of high levels of fatigue5 at Top of Descent6 (TOD) during night and late finish FDPs compared to the baseline FDP .
Night FDPs, both longer and shorter than 10 hours, were associated with an increased probability of high fatigue at TOD. This is not fully reflected in the current FTL regulation and guidance material. The regulation and guidelines explicitly note the need for appropriate fatigue risk management and the importance of obtaining sufficient sleep in relation to night duties longer than 10 hours, but not for those shorter than 10 hours.
No significant increase of probability of high levels of fatigue at TOD was found for disruptive schedules classed as early start FDPs. A marginal increase was found for mixtures of disruptive FDPs . The factors that best predicted increased odds of high fatigue at TOD varied by FDP type. This suggests that fatigue mitigation measures should be based on various fatigue management strategies and tailored to FDP type and operator context. Since there are multiple other more influential determinants, the increased fatigue at TOD during longer night duties may be difficult to effectively control by merely adjusting the FDP duration.
It is recommended to amend the definition of ‘night’ FDP to reflect the different subgroups of ‘night ‘ FDPs. This would help operators to design effective fatigue risk measures.
The current FTL regulation does not require operators to apply appropriate fatigue risk management to late finish FDPs. It is recommended to require operators to apply appropriate fatigue risk management to mitigate the fatiguing effect of late finish FDPs, regardless of FDP duration.
The study results indicated that high fatigue at TOD during night FDPs of both long duration (> 10h) and shorter duration (≤ 10h). It is recommended to require operators to apply appropriate fatigue risk management to mitigate the fatiguing effect of all night FDPs, regardless of FDP duration.
Within night FDPs, duty periods that end at 6.00 or later combined with a start at 1.59 or earlier show the greatest probability of high fatigue at TOD. It is recommended that the regulation define this category of FDP and require operators to pay specific attention to these FDPs when applying fatigue risk management.
The study found shorter prior sleep to be a predictor of high fatigue at TOD for all night FDPs. The current guidance material for night duties (GM1 CS FTL.1.205) stipulates that it is ‘critical for the crew member to obtain sufficient sleep’ for night duties longer than 10 hours. It is recommended that the GM be amended to state that it is critical for the crew member to obtain sufficient sleep before all night duties, regardless of FDP duration.
The analysis provides evidence of high fatigue at TOD during night FDPs. This seems to be fairly independent of FDP characteristics (e.g. start and end times, duration), as long as the FDP in question meets the criteria for a night FDP. The amount of prior sleep is the main predictor of eventual fatigue, therefore we recommend that for night FDPs, operators should be required to promote optimum use of sleep opportunities (i.e. before reporting and during the FDP).