Now, what kind of a question is that? Isn’t it obvious that working just 7 hours must be better for flight safety than working for 10 hours and thirty minutes? Come on! But, is it such a foolish question? If you think about it, we are, after all, comparing apples and pears. Our comparison leaves out three and a half hours of work to be done ‘elsewhere.’ This particular rule (max FDP) is not there to limit the overall amount of work. It is designed to restrict the duration of flight duty periods in isolation, and changing the rule limit will primarily force a redistribution of work, not a reduction of it. Assuming that an operator can still fit in all of the required work with the same crew (which is not certain given this drastic change, but let’s assume), the impact of reducing max FDP down to just 7 hours would be:
For every two flight duties in the past (up to 10:30 in duration), we would instead need three to reach the same amount of hours worked (21:00).
Assuming 2 hours of wakefulness before and after each duty, these 21 hours of work would ‘occupy’ 33 hours (11 x 3) on the rosters instead of the previous 29 hours (14:30 x 2). This will leave the crew with less opportunity for sleep, which will likely increase sleep debt.
With more duties encroaching on good sleep opportunities, the crew would experience fewer days off, more sleep debt, and more consecutive FDPs that are ‘challenging.’ So, perhaps it’s not such a foolish question after all? Could it be that, for control of fatigue risk, another value than 10:30 is the optimal one? 10:00? 11:00? Could the optimum even differ between operators and the flight schedule?
Recently, this type of rule optimization has become possible using standard production tools and bio-mathematical models in combination. Realistic working patterns can be produced at scale, and a quantification of any proposed change to the rules can be made. This is not only helpful to regulators seeking to improve regulations but also to operators wishing to better align their internal working agreements and practices with human physiology. Welcome to read more here.