Radio Communication Failure in the Terminal Area
At 11:15 UTC, a radar controller is working an IFR arrival, Flight NGA221, a Boeing 737, descending to FL110 on an arrival route 40 NM from destination. The aircraft was cleared to FL110 and told to expect the ILS runway 27. The controller has not received a reply for 7 minutes despite repeated calls on 119.7 and 121.5. The aircraft's SSR code changes to 7600. A Dash 8 is 15 NM behind on the same route, descending to FL130. Weather is VMC: wind 270/10 kt, visibility 10 km. Runway 27 is in use; the airport has a second runway available. The controller must apply radio communication failure procedures, protect the airspace around NGA221, and sequence the Dash 8 without knowing NGA221's intentions.
1. What are the controller's immediate actions on seeing SSR 7600?
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Confirm the code and attempt contact on the emergency frequency and on the published backup frequency. Notify the adjacent sector and the supervisor. Protect the aircraft's route by stopping climbs or descents that could conflict with it. The Dash 8 at FL130 is 1,000 ft above NGA221 at FL110; that is standard RVSM vertical separation, but if NGA221 follows the lost-communication procedure and climbs, the conflict could develop. Therefore keep the Dash 8 at FL130 or turn it away, and do not clear it to descend until NGA221's position is assured.
Do not vector NGA221 without radio contact. Assume it will follow its last clearance and the published lost-communication procedure. Pass traffic information to other aircraft and protect the final approach path for runway 27.
2. What will the pilot of NGA221 most likely do under ICAO radio failure procedures?
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The pilot should squawk 7600, maintain the last assigned level for the prescribed period (commonly 7 minutes), then climb to the minimum safe altitude, proceed to the destination, and commence the published approach. In this case, expect NGA221 to maintain FL110 for the 7-minute period, then climb and continue toward the ILS runway 27. The controller should therefore protect both FL110 and the likely climb path.
ATC should clear the airspace, hold or divert other traffic, and expect NGA221 on final. Do not assume the aircraft has crashed or diverted; the SSR 7600 is positive evidence of a radio failure. Keep attempting contact and listen for relayed reports from other aircraft.
3. How should the Dash 8 be sequenced, and what should happen if NGA221 lands without further contact?
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Keep the Dash 8 at FL130 or vector it clear of NGA221's route. Do not let it overtake or descend into the airspace NGA221 may occupy. Pass traffic information: Dash 8, traffic a Boeing 737, radio communication failure, squawking 7600, maintaining FL110, expect delay. If the Dash 8's fuel becomes a concern, ask for endurance and consider diversion.
If NGA221 lands without further contact, allow it to vacate, then release the Dash 8 for approach. As a precaution, ask the tower to alert emergency services because a radio-failure landing may still involve an abnormal situation. After landing, obtain the pilot's report, confirm the aircraft is safe, and file an occurrence report. Preserve recordings and note the times of lost contact, 7600 display, and landing.