Sequencing Six Inbound Aircraft at Mehrabad with a Medical Emergency and Minimum Fuel
Mehrabad Approach (OIII) is working one runway, 29L, in VMC with wind 290/08 kt and visibility 10 km. Six aircraft are inbound for landing. IRB221 is 25 NM east descending FL180; IRB305 is 18 NM west at FL120; IRB418 is a heavy 12 NM final at 4,000 ft; IRB590 is 20 NM north at FL150 and reports minimum fuel; IRB777 is 35 NM south at FL240 and declares a medical emergency, requesting priority; and a military Falcon is 30 NM east at FL200 requesting a practice ILS. The radar display shows all traffic. The airport has no parallel runway available and the final approach is 12 NM long. The controller must build a sequence before the emergency aircraft reaches 15 NM. The tower reports birds over the threshold. IRB305 is a light aircraft and wake turbulence separation applies behind IRB418.
1. Establish the priority order and justify it against the traffic positions and fuel states.
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Priority does not mean putting an aircraft on the runway ahead of an aircraft already stabilized on short final. IRB418 is a heavy at 12 NM final and will land first unless there is a compelling reason to break it off. IRB777 has declared a medical emergency and must be given priority for the next available landing; it is 35 NM south at FL240, so it needs descent and vectors without delay. IRB590 has minimum fuel and should be next after the emergency, but minimum fuel is not the same as an emergency unless the crew declares a fuel emergency. IRB221, IRB305, and the military Falcon follow. The military practice ILS should be refused or delayed because it adds traffic and does not have operational priority. If IRB777's condition is time-critical, the controller can ask IRB418 to expedite or go around, but that decision must be based on a clear statement from the emergency aircraft, not on the label alone.
2. Describe the sequence, separations, and holding instructions you would issue.
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Land IRB418 first if it remains stable; issue wake turbulence caution to IRB305 behind the heavy. Bring IRB777 directly into the sequence behind IRB418 with vectors to a 5 NM final spacing, and give it priority over IRB590. Put IRB590 next, then IRB221 and IRB305. Send IRB221 to a holding fix east at FL180 or descend it to a downwind leg, and keep IRB305 west until the sequence is clear. Deny the military Falcon the practice ILS and instruct it to remain clear of the approach. Use 5 NM radar separation in the approach sequence, increasing behind the heavy if the following aircraft is light. Because the final is 12 NM long and the emergency is 35 NM out, the controller has time to descend IRB777 but not to let it overtake IRB418 on final. The key judgement is to protect the stable aircraft on short final while making the emergency number one for the next landing.
3. What phraseology would you use for the emergency and minimum-fuel aircraft, and what should be recorded?
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For the emergency: 'IRB777, roger medical emergency, cleared direct to the runway 29L final, descend 4,000 ft, expect priority landing, report 10 NM.' For minimum fuel: 'IRB590, roger minimum fuel, expect landing after the emergency traffic, maintain FL150, hold north of the field.' Avoid promising a landing clearance that cannot be delivered. Record the time IRB777 declared the emergency, the nature if known, the priority given, the sequence, and the fuel state reported by IRB590. If IRB590 later declares a fuel emergency, the priority order must be reassessed because a fuel emergency can become more immediate than a medical case depending on the declared urgency. The record should also show that the military practice ILS was refused and why.