Rapid depressurisation at FL360 with opposite-direction traffic
At 03:40 local you are the sole controller on a combined area/approach sector; your assistant is on a 20-minute break. A Boeing 737 at FL360, 25 NM ahead of your boundary, reports 'rapid depressurisation, emergency descent to FL100'. Opposite-direction traffic: a cargo 747 at FL340, 40 NM ahead of the 737, and a business jet at FL320, 60 NM ahead. The 737 is in a right turn, descending at 6,000 ft/min, and requests 'clear airspace'. The 747 reports a TCAS traffic alert. The adjacent sector is staffed but busy. The 737's destination is 120 NM away; a suitable alternate is 60 NM away. Radar coverage in the area continues to FL100.
1. What are your immediate actions and clearances?
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Treat it as an emergency. Clear the 737: 'Descend unrestricted to FL100, turn right heading 090, clear of traffic, report leaving FL360.' The turn gets it out of the opposite-direction track before it descends through FL340 and FL320; the unrestricted descent gives the crew flexibility. Tell the 747: 'Traffic, 12 o'clock, 20 NM, emergency descent, turn right heading 180, descend to FL300' or as appropriate, but do not issue a clearance that conflicts with its TCAS RA.
Ask the 737 for persons on board, fuel, nature of the problem and intentions, without overloading it. Stop other traffic entering the area. The first priority is lateral separation, then vertical, then information. The 737's emergency authority allows it to deviate from the rules, but ATC still provides separation to the extent possible.
2. How do you handle the 747's TCAS alert and the coordination with the adjacent sector?
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TCAS RA takes precedence over ATC clearances. Ask the 747: 'Report TCAS RA', and do not instruct a manoeuvre that contradicts it. If the RA is to climb or descend, let the crew follow it, then provide traffic and, when clear of conflict, issue a new clearance.
Coordinate with the adjacent sector before the 737 crosses the boundary: 'Emergency descent, FL360 to FL100, heading 090, request unrestricted.' The adjacent controller must protect the airspace ahead. The business jet at FL320 may need to be turned or stopped. Do not hand off the emergency aircraft until the receiving controller has the full picture. Once the 737 is at FL100, confirm its intentions and hand it to approach for the diversion.
3. What do you do after the event, including human factors and reporting?
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After the aircraft is safe, file the occurrence report; an emergency descent is a serious incident and should be reported under the ANSP scheme and to the IAA under Regulation (EU) 376/2014 within 72 hours. Preserve voice and radar recordings.
Then look after the controller. You have been alone for 20 minutes, the assistant is on a break and the workload was high; request relief before the next busy period and write a factual statement while it is fresh. The human-factors lesson is not that the controller was slow, but that single-manning during a break creates a latent risk; the break should be covered. Under a just culture, the report should be used to fix staffing and procedure, not to blame. If fatigue was a factor, report it through the safety system.