In the event of an emergency, air traffic control applies the so-called “ASSIST” principle. This stands for Acknowledge, Separate, Silence, Inform, Support and Time.
Acknowledge
When a pilot reports an emergency, the air traffic controller acknowledges the call. From that moment on, he or she records the aircraft’s position and course so that this data is available as and when needed.
Separate
An aircraft in an emergency situation takes priority over all other traffic and must be able to make an uninterrupted approach to the airfield chosen for its landing. The air traffic controller ensures adequate separation from other traffic.
Silence
If radio communication with the aircraft is possible, it is limited to the most essential information. In principle, the air traffic controller only provides the pilot with details he or she specifically asks for. This avoids the pilot, who needs to concentrate upon flying the aircraft, being distracted by useful but non-essential information. Silence gives pilots the time and space they need to focus upon taking the correct action. A separate emergency frequency is available so that the pilot and the controller can communicate one-to-one, without interruptions from other aircraft.
Inform
The air traffic controller informs the control tower supervisor of the emergency as quickly as possible, stating the nature of the situation (for example, a technical problem, a hijacking or a bomb warning), what he or she has already done in response and what airfield the pilot has chosen for a precautionary or emergency landing. The pilot is informed of the measures taken in response to the situation.
Support
As far as possible, all requests by the pilot are accepted. For example, he or she may ask to jettison fuel, for specific information (about weather conditions, say, or the plane’s altitude) or to land on a particular runway.
Time
The air traffic controller gives the pilot as much time as possible to deal with the problems on board.
