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EASA FTL: Understanding Flight Time Limitations

In commercial aviation, safety is the overriding priority. Fatigue management is strictly governed by international and national regulatory agencies, such as IATA, the FAA (in the US), and EASA (in Europe) (formerly JAR).

For a European carrier like Norwegian, the EASA FTL (Flight Time Limitations) framework dictates the absolute boundaries of crew scheduling. In Rave, these rules are modeled as Final Rules because violating them makes a schedule legally impossible to fly.

1. Flight Duty Period (FDP)

The Flight Duty Period (FDP) is the core metric for fatigue. It begins when a crew member reports for duty and ends when the aircraft engines are switched off at the end of the final flight of that duty.

gantt
    title Anatomy of a Flight Duty Period (FDP)
    dateFormat  HH:mm
    axisFormat %H:%M

    section Ground
    Briefing (Report) :a1, 06:00, 1h
    Debriefing (Release) :a2, 14:00, 30m

    section Flying
    Flight 1 (Block Time) :f1, 07:00, 3h
    Sit Time :s1, 10:00, 1h
    Flight 2 (Block Time) :f2, 11:00, 3h

    section Regulatory
    FDP (Flight Duty Period) :active, 06:00, 8h
    Total Duty Time :100, 06:00, 8.5h

Factors Limiting FDP

The maximum allowable FDP is not static. A Rave Developer must program logic that dynamically adjusts the maximum FDP based on:

  1. Time of Day: Duties starting during the "WOCL" (Window of Circadian Low, typically 02:00–05:59) have severely restricted maximum FDPs.
  2. Number of Sectors: The physical toll of multiple take-offs and landings reduces the maximum FDP. Each sector beyond a certain threshold usually subtracts 30 minutes from the max FDP.
  3. Acclimatization: If a crew member crosses multiple time zones, their internal body clock is disrupted, triggering stricter limits.

2. Rest Requirements

Rest is heavily regulated to ensure crew recovery.

  • Minimum Daily Rest: Typically, a crew member must receive at least 12 hours of rest, or rest equal to the length of the preceding duty period (whichever is greater).
  • Reduced Rest: Under strict conditions, rest can be reduced, provided compensatory rest is given subsequently.
  • Weekly/Monthly Rest: Regulations enforce minimum uninterrupted rest periods over 7-day and 28-day rolling windows.

3. Implementation in Optimization

When building the optimization models, FTL rules are implemented as hard constraints. If an optimization engine generates a sequence of flights that violates an EASA FTL rule, the sequence is illegal and pruned from the search space.