Fourth Sector of a Night Freight Run at the Circadian Low
A Beechcraft King Air 200 freight run has been extended to a fourth leg after a delayed cargo drop. The crew reported for duty at 19:00 the previous evening, had a two-hour standby, and the captain has slept four hours in the last 22. It is now 04:50; departure from Ondangwa is at 05:10 for the 55-minute return to Eros. The captain is 52, on his sixth consecutive night shift, has had two cups of coffee in the last hour and takes no medication. In the last 20 minutes he has twice lost the thread of an ATC clearance, has let the altitude drift 200 ft low, and has yawned repeatedly. The first officer has 250 hours total and 15 at night. The destination forecast is fine, but Eros has a single lit runway and no ILS; the return requires a visual circuit.
1. Rank the fatigue contributors in this scenario and explain what the 04:50 timing adds to the risk.
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Contributors, in rough order of weight.
- Time awake and sleep debt - about 22 hours awake on four hours' sleep. Laboratory performance at this level of sleep restriction is comparable with being over a legal alcohol driving limit.
- Circadian low - 04:50 sits inside the window of circadian low (roughly 03:00–05:00), when core temperature, alertness and vigilance bottom out. This is the worst window in which to launch into the highest-workload phase.
- Cumulative exposure - sixth consecutive night shift; circadian adaptation is incomplete and recovery sleep has been short.
- Workload and crewing - four sectors of night freight, no cabin crew, and a 250-hour first officer with 15 night hours who cannot meaningfully relieve the captain.
- Late caffeine - masking, not restoring, and likely to fragment the rest that follows.
What the symptoms add. Lost clearance thread, a 200 ft altitude deviation and repeated yawning are objective performance failures - microsleeps - not subjective tiredness. A crew that cannot hold ±200 ft in cruise cannot fly a visual circuit to a single lit runway.
2. What mitigations are realistically available, and what decision would you make about the return leg?
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Mitigations that work tonight: 150–200 mg caffeine about 30 minutes before the expected low; cold air and ventilation; deliberate verbal callouts and active monitoring by the other pilot; a controlled rest of 20–30 minutes on the ground before departure, one pilot at a time, with the other guarding the aircraft.
What does not work: 'it is only 55 minutes'. The exposure is not the cruise - it is the departure, the visual circuit and the landing, which is precisely where residual alertness is lowest.
Decision. Do not launch with the captain as pilot flying. Options in order: (a) take 45–60 minutes' rest on the ground and depart after 06:00, outside the circadian low, accepting a duty extension only if the operator's scheme permits it; (b) if the schedule cannot move, stop the night programme and reposition to day operations. Making the first officer pilot flying trades one risk for a larger one - 15 night hours into an unlit-aid circuit at the circadian low. Rest, then fly, is the only defensible answer.
3. The captain says he is 'wide awake now' after the coffee. How should that self-assessment be weighted, and what does good practice require of the operator and the first officer?
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Subjective alertness recovers before performance does. A caffeine-induced 'second wind' typically peaks 30–60 minutes after ingestion and is followed by a sharper dip; the feeling of wakefulness is therefore a poor predictor of the ability to hold an altitude, read a checklist or fly a circuit. Objective evidence - the lost clearance, the 200 ft deviation - outranks the self-report, and a commander who has just demonstrated microsleeps is the least reliable judge of his own fitness.
Operator: a fatigue management approach with defined maximum duty and night-duty limits, a no-blame fatigue reporting channel, and a rostering rule that limits consecutive night shifts. First officer: an obligation to speak up - a junior crew member who says nothing is complicit. Commander: retains the authority to decline the flight, and should file a fatigue report so the occurrence is captured rather than absorbed into the schedule.