Fatigue and the Third Sortie of the Day
A remote pilot has flown two 40-minute sorties since 06:00, with a 30-minute break between them, and is now preparing a third sortie at 14:30 in 30 °C heat. The pilot skipped lunch and has been standing in direct sun for most of the day. The pre-flight checklist is being completed from memory rather than the printed card, and the pilot has already twice mis-set the return-to-home altitude. The observer notes the pilot is slower to respond to radio calls and has become irritable about a minor procedural query. The aircraft is a 7 kg multirotor, and the mission is a routine perimeter inspection with no time pressure.
1. Assess the pilot's fitness to fly the third sortie, citing the specific human-factors cues.
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The pilot is showing a cluster of fatigue and heat-stress indicators that together make the third sortie unsafe as planned:
- Cumulative flight time with only short breaks, plus skipped food and prolonged heat exposure, degrade attention and decision-making.
- Completing the checklist from memory and mis-setting the RTH altitude twice are errors of omission and slips consistent with reduced vigilance.
- Slower radio response and irritability are behavioural signs of fatigue and heat strain.
No single cue is decisive, but the combination is. The correct judgement is to stand down, not to 'push through' a routine task with no time pressure.
2. What should happen before any further flight, and how would you structure the rest of the day?
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Stand down and recover:
- Move to shade, rehydrate, and eat; allow a meaningful rest period rather than a token break.
- Re-brief the checklist and require it to be read from the printed card, with the observer cross-checking critical items such as RTH altitude.
- Reassess before flight: if the pilot still shows slowed responses or irritability, do not fly that day.
For the rest of the day, schedule sorties with longer breaks, rotate the pilot with the observer for monitoring duties, and avoid the hottest part of the day. The mission has no time pressure, so there is no justification for flying a degraded pilot.
3. How does the observer's role change the risk picture?
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The observer is the second set of eyes and the cross-check on the pilot's degraded performance. The observer's note about slower radio response and irritability is exactly the kind of evidence that should trigger a stand-down, and the observer should be empowered to call it.
Operationally, the observer should:
- Read the checklist aloud and confirm critical settings rather than trusting the pilot's memory.
- Monitor the pilot for heat and fatigue signs as well as the airspace.
- Have the authority to halt the sortie without needing the pilot's agreement.
Treating the observer as a passive passenger removes the very barrier that catches fatigue errors.