Four-Sector FDP Extension After a Weather Closure
A two-pilot crew is scheduled for a commercial IFR flight of four sectors in a twin-engine turboprop. Report time is 04:30, first departure 05:00, and planned final landing 16:30. The authority’s flight time limitation scheme, reproduced in the operator’s manual, sets a maximum basic flight duty period (FDP) for two-pilot crews of 13 hours for one or two sectors, 12 hours for three or four sectors, and 11 hours for five or six sectors. The commander may extend the FDP by up to 2 hours only for unforeseen circumstances that arise after the FDP has started; the extension must not be pre-planned and requires compensatory rest. At 13:00, after the second sector, a destination weather closure delays departure by 2 hours 20 minutes. The revised final landing is 18:50. The crew had 9 hours of rest before report and feels fit. The operator asks the commander to ‘use discretion’ to complete the programme.
1. Calculate the planned and revised FDP. Determine the maximum FDP available with the commander’s extension and state whether the revised schedule can be completed.
Read the worked answer
Planned FDP = 16:30 − 04:30 = 12 h 00 min. With four sectors, the basic maximum is 12 h, so the planned schedule is exactly at the limit and is legal.
Revised FDP = 18:50 − 04:30 = 14 h 20 min.
The commander’s extension is capped at 2 h, so the absolute maximum is 12 h + 2 h = 14 h 00 min. The revised schedule exceeds even that maximum by 20 min. Therefore the flight cannot be completed as revised, regardless of how fit the crew feels. The extension cannot be used to convert an over-limit schedule into a legal one; it is a limited discretionary tool for unforeseen events after the FDP has begun.
2. Explain whether the commander’s discretion is available in principle, and what conditions would have to be satisfied before any extension could be used.
Read the worked answer
The weather closure is an unforeseen circumstance arising after the FDP started, so the extension is available in principle. It is not available merely because the operator asks for it, and it cannot be pre-planned. Before extending, the commander would need to satisfy the scheme’s conditions: the delay must genuinely be unforeseen; the extension must not exceed 2 h; the commander must consider cumulative fatigue, rest before report, sectors flown, and any disruption; and compensatory rest must be arranged and recorded. The extension must also be entered in the operational record. In this case those conditions do not rescue the schedule because the arithmetic already exceeds the 2 h cap.
3. If the delay had been 1 hour 20 minutes instead, giving a revised final landing of 18:10, how would your answer change?
Read the worked answer
Revised FDP would be 18:10 − 04:30 = 13 h 40 min. The basic maximum is 12 h, so an extension of 1 h 40 min would be needed. That is within the 2 h cap and is for an unforeseen event after the start of the FDP, so the commander could legally extend, provided the fatigue assessment is satisfactory, the extension is recorded, and compensatory rest is arranged. The crew would still need to be fit and the commander would need to consider whether the remaining sectors can be completed without reducing the available rest. The decision is discretionary, not automatic.