Fatigue and a Marginal Night Approach into Tehran
It is 01:40 local. You are captain of a two-pilot crew on the fourth sector of a duty that began at 07:10. The first officer mentions a headache and says he slept only four hours because of a family issue. The flight from Mashhad to Tehran is 1 h 20 min; destination weather is 300 ft vertical visibility, RVR 550 m, calm wind, and the ILS minima are 200 ft/550 m. Fuel allows one approach at destination, a diversion to Isfahan (25 min), and 30 minutes holding. During descent the first officer misreads the QNH and calls '1003' instead of '1013'; you catch it. On final, the autopilot disengages and the localizer starts to drift. You are both instrument-rated and current.
1. Identify the human-performance threats and explain how they affect the approach.
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Threats: acute fatigue (4 h sleep), circadian low at 01:40, fourth sector, possible 18+ h duty, headache, and high workload in low visibility. Fatigue degrades monitoring, slows reaction, increases fixation, and reduces the first officer's ability to catch errors. The QNH misread is a warning sign: if one gross error occurred, the monitoring loop is degraded. The autopilot disconnection and localizer drift add workload. The approach is at minima with one approach fuel; the crew should treat the fatigue as a no-go factor, not a personal weakness.
2. What should you do after the QNH error and autopilot disconnection?
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Take control, go around, and do not continue the approach. Verify QNH from ATIS and cross-check both altimeters. Ask the first officer directly about fitness and whether he can continue; if there is doubt, divert to Isfahan. Fuel allows one approach, diversion, and 30 minutes holding, so there is no fuel pressure to force a second approach. Use the go-around to reduce workload and make a deliberate decision. If the first officer is unfit, consider a single-pilot diversion or request priority, depending on the operation.
3. How would you communicate the decision to the first officer and ATC?
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Use closed-loop communication: I have control, we are going around, set go-around thrust, flaps 15, positive climb. Then: We are diverting to Isfahan; advise ATC. Explain the reason to the first officer without blame: the QNH error and fatigue mean the approach should not continue. After landing, complete an occurrence/fatigue report and consider whether the duty was legal. ATC call: ABC123 going around, request diversion to Isfahan, reason crew fatigue.