Mayday from a Twinjet
En-route sector. A B738 at FL 340, 90 NM from destination, reports left engine failure and requests descent to FL 240 and diversion to an airport 60 NM south. Opposite-direction traffic is at FL 330, 40 NM ahead. Another aircraft at FL 350 is 15 NM behind the B738 on the same track. The B738 states it cannot maintain FL 340. The sector is using radar control with 5 NM separation and 1,000 ft vertical separation.
1. What are your immediate actions and phraseology?
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Acknowledge the emergency and establish priority: 'B738, roger MAYDAY, descend to FL 240, turn right heading 180, squawk 7700.' Give the descent and turn promptly so the aircraft is not left at a level it cannot maintain. Do not wait for a full readback before issuing the avoiding turn. Advise the aircraft that the airport 60 NM south is being notified and ask for fuel endurance and number of persons on board when workload permits. The emergency does not remove the controller's responsibility to provide separation from other traffic, but it changes the priority and may require expeditious vectors.
2. How do you separate the B738 from the opposite-direction traffic at FL 330 and the following aircraft at FL 350?
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The B738 is descending from FL 340 and cannot maintain level, so the immediate risk is the opposite-direction aircraft at FL 330. Issue a turn to keep the B738 clear laterally, and coordinate with the adjacent sector before the aircraft crosses the boundary. Do not rely on the B738 reaching FL 240 before the opposite traffic passes. The following aircraft at FL 350 should be stopped at FL 350 or given a vector, and must not be allowed to descend into the B738's path. Once the emergency aircraft is established at FL 240 and clear of the opposite traffic, normal separation can be rebuilt, but the controller should keep the emergency route protected until the aircraft is handed off.
3. What coordination and information should be passed to the destination, the next sector and the supervisor?
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Pass a concise emergency summary to the next sector: callsign, nature of emergency, level, heading, squawk, requested airport and fuel state. Notify the destination tower/approach and the airport emergency services so that priority landing and ground support are ready. Inform the supervisor and record the time the MAYDAY was received. Do not overload the crew with non-essential questions during the descent; obtain details once the aircraft is stable. The handover must include the emergency status explicitly so that the next controller does not treat it as routine traffic.