Definition
Crew duty time (often abbreviated CDT) refers to the total elapsed time from the moment a flight crew member reports for an assigned duty — whether a flight, standby, or ground task — until the moment they are formally released from all obligations. Regulatory authorities worldwide impose maximum duty-time limits to prevent fatigue-related errors and accidents. These limits vary by jurisdiction, type of operation, time of day, number of flight sectors, and whether the crew member has been on standby prior to flying. Under EASA regulations, crew duty-time limits are defined in the Flight Time Limitations (FTL) rules within ORO.FTL, which specify maximum daily flight duty periods, cumulative flight-time limits over 28-day and annual periods, and minimum rest requirements between duties. The FAA addresses equivalent concerns through Part 117 for airline pilots and Part 135 for on-demand operations, each with its own set of limits and rest requirements. HEMS and other specialised operations often have additional or modified limits reflecting the demanding nature of the missions. Duty time is distinct from flight time: a crew member who spends two hours on pre-flight preparation, four hours flying, and one hour on post-flight duties has accumulated seven hours of duty time but only four hours of flight time. Both metrics must be tracked independently because different regulatory limits apply to each. Exceeding either limit is a regulatory violation that can result in enforcement action against both the operator and the individual crew member.
Why It Matters for Flight Schools
Tracking crew duty time accurately is one of the most operationally critical and error-prone tasks in aviation management. The calculations are straightforward for simple operations with regular schedules, but they become complex when crews operate across time zones, transition between standby and active flying, or work split-duty patterns. A single miscalculation can result in a crew member exceeding their legal duty limit mid-mission, potentially forcing a diversion or cancellation. For operators with multiple bases, fleet types, and mission profiles — such as a HEMS provider that also conducts charter and training flights — the duty-time tracking challenge is compounded by the need to aggregate hours across different operational categories. A pilot who flies a training sortie in the morning and a HEMS mission in the afternoon has accumulated duty time in both activities, and the combined total must not exceed the applicable limit.
How Aviatize Handles This
Aviatize automatically calculates crew duty time from dispatch and sign-off records, applying the correct regulatory limits based on the operation type, crew role, and applicable FTL rules. The smart planning module displays remaining available duty time for each crew member in real time, allowing dispatchers and planners to make informed assignment decisions before accepting new missions. The compliance and auditing module maintains a complete duty-time history for every crew member, generating reports formatted for regulatory inspections and internal safety reviews. Automated alerts warn operations managers when crew members are approaching duty limits, providing sufficient lead time to arrange replacements and avoid last-minute operational disruptions.