Night Fatigue and the Approach Decision
You are a commercial pilot on the third consecutive night duty, having reported at 22:00 and now at 04:30 on the fourth sector. You have had about 5 hours of sleep in the last 24 hours and your circadian low is around 04:00-06:00. On the ILS to a coastal airport, the tower reports wind 090/08, visibility 4,000 m in mist, and the approach lights are on. You feel heavy-eyed, have missed two radio calls in the last 10 minutes, and catch yourself misreading the altimeter twice on the same approach.
1. Identify the human-performance factors at work and explain why the missed calls and altimeter misreads are warning signs rather than minor errors.
Read the worked answer
Three factors combine: sleep debt (about 5 hours in 24), circadian low (04:00-06:00, when alertness and vigilance are at their lowest), and cumulative duty across consecutive nights. Together they produce microsleeps, narrowed attention and degraded monitoring, which is exactly what missed radio calls and repeated misreads look like.
The errors are not random slips; they are the signature of a fatigued operator. A rested pilot may miss one call, but two missed calls plus two altimeter misreads on the same approach indicate that the monitoring loop is failing. In a two-crew aircraft the correct response is to verbalise the fatigue, hand over the approach to the other pilot if possible, and consider a go-around or a diversion to a better-equipped aerodrome rather than pressing on because the weather is legal. The examiner is testing whether you treat fatigue as an operational threat with a decision, not as a private discomfort.
2. What are your options and which do you choose?
Read the worked answer
Options: continue the approach, hand control to the other pilot and continue as monitoring pilot, go around and divert, or land and declare unfit for further duty.
I would hand over control, brief the other pilot on my state, and continue only if the other pilot is fresh and the approach is stable. If there is any doubt, go around and divert. After landing, I would file a fatigue report and decline the next sector; the regulation requires that a pilot not fly when unfit, and cumulative night duty is a recognised cause. The judgement point is that the legal weather does not make the approach safe when the crew's performance is degraded, and that the decision must be made before the approach becomes unstable, not after.