Did you know that for a typical airline, there are often 100-300 different rules governing crew pairing and roster construction? Examples of these rules are maximum block and duty hours, minimum rest, and also many other types of rules to avoid certain scheduling combinations. The regulatory rules are in clear minority - most of the rules are added over time, in dialogue between crew representatives and the operator.
Each rule (or 'constraint') added to an operators 'rule set', either comes at a cost, or is of no practical importance. If a rule is of importance, it will remove otherwise attractive 'solution space' for the planning optimizers, something that will result in more costly* solutions. The new solutions may even contain something considered worse than the undesirable aspect that was removed by the new rule. Add a new rule restricting duty time during the night, and it will result in producing more night duties and potentially more consecutive ones.
Unless an undesirable solution aspect must never ever happen again, not even once in a million rosters (something that is rarely the case) it is much better to instead use penalties suppressing these aspects close to non-existence. This approach will keep the solution space available for exploration, allowing the optimizer to travel paths possibly needed for finding the way to the optimium.
Fortunately, the above is also valid the other way around; each constraint that can be removed or 'relaxed' is a golden opportunity for improvement. However, while it is relatively easy to add a new rule, removing them comes with more effort. Please find in this document a methodology for re-structuring a rule set and harvesting benefits while more efficiently addressing fatigue risk. Your constraints are your opportunities! Enjoy.
*) In crew planning the 'cost' that guides the optimizer reflects all aspects that an operator values. To notgrant a crew members' bid will be a cost to the planning optimizer.
Comentários