Interception of an Unknown Aircraft Near a TMA
A military air defence controller advises the TMA controller that an unidentified aircraft has entered the TMA boundary at FL280, squawking 7600, not on any flight plan, and not responding to calls on 121.5. The aircraft is tracking toward the extended centreline of the main runway at SBZZ, a busy international aerodrome. Two civil arrivals are on the downwind at 6000 ft and 7000 ft. The military controller requests that the TMA controller clear the airspace and provide information to the intercepting fighter, which is 15 NM behind the unknown aircraft.
1. What is the TMA controller's role in an interception, and what should be done with the civil traffic?
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The TMA controller's role is to support the interception by clearing the airspace and providing information, not to direct the interception itself. The intercepting fighter is under the military controller's control; the TMA controller coordinates with the military controller and with the civil traffic.
Actions:
- Clear the airspace along the unknown aircraft's track and the fighter's approach path. The two civil arrivals on downwind at 6000 ft and 7000 ft are directly in the potential conflict zone if the unknown aircraft descends. Instruct both to break off the approach, turn away from the extended centreline, and climb or descend as directed to clear the area. Give them traffic information about the unknown aircraft and the interception.
- Coordinate with the military controller: confirm the fighter's altitude, track, and the frequency to be used, and pass the civil traffic positions.
- Do not attempt to communicate with the unknown aircraft on the TMA frequency alone; continue to try 121.5 and, if possible, the emergency frequency, but do not delay the civil traffic instructions.
- Inform the aerodrome operator and the approach unit, and be prepared to suspend arrivals.
- Record the sequence of events.
2. The unknown aircraft squawks 7700 and begins a descent toward the aerodrome. How does this change the controller's priorities?
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A 7700 squawk indicates the aircraft is declaring an emergency, which changes the priority from 'unknown intruder' to 'aircraft in distress'. The controller must now treat the aircraft as an emergency and provide assistance, while still managing the interception.
Priorities:
- Protect the aircraft: clear the airspace beneath and around its descent path, and keep the civil traffic well clear. The two civil arrivals should remain off the approach and be held or vectored away.
- Establish communication if possible: try 121.5 and the TMA frequency; if contact is made, ask for the nature of the emergency, persons on board, fuel, and intentions.
- Coordinate with the military controller: the fighter should be instructed to maintain a safe distance and not to interfere with the emergency aircraft's descent. The interception may continue as an escort, but the emergency takes precedence.
- Alert ARFF and the aerodrome operator, and prepare for a priority landing.
- If the aircraft lands, pass the information to the tower and the ground services. If it does not, continue to provide assistance and record all actions.