The procedures outlined herein are intended as a general guide to air traffic services personnel. Air traffic control units shall maintain full and complete coordination, and personnel shall use their best judgment in handling emergency situations.
If the pilot of an aircraft encountering a state of emergency has previously been directed by ATC to operate the transponder on a specific code, this code will normally be maintained until the pilot has been advised otherwise. However, the fact that the pilot squawks on 7700 helps the coordination between controllers. This does not apply to urgency calls.
The following signals, used either together or separately, mean that grave and imminent danger threatens, and immediate assistance is requested:
The following signals, used either together or separately, mean that an aircraft wishes to give notice of difficulties which compel it to land without requiring immediate assistance:
The following signals, used either together or separately, mean that an aircraft has a very urgent message to transmit concerning the safety of a ship, aircraft or other vehicle, or of some person on board or within sight:
A pilot will declare an urgency call by using the spoken words PAN PAN (3x) followed by his message when he is in a condition concerning the safety of the aircraft or some person on board, but which does not require immediate assistance.
Urgency calls take priority over all other messages, except distress calls. As an active controller, you shall acknowledge the urgency call
ATC: [aircraft Call sign] Roger PAN PAN at time [hhmm]Z.
There is no need to give the aircraft absolute priority. However an expeditious ATC service is required. Usually a pilot will let you know if he requires anything from you. If not given, you can try to get any information you think is necessary to enable you giving the pilot the best service possible.
A pilot may tell you to standby, because he is busy or doesn't have an answer to your question just yet. But you can trust that he will get back to you when he can.
How to handle an urgency call will be different every time. There are some aspects which are Important to remember, for instance:
Manoeuvring instructions to an aircraft experiencing engine failure should be limited to a minimum. For instance, climb instructions shall be avoided or suitable to the performance of the airplane.
A pilot will issue a distress call by using the words MAYDAY (3x) followed by his message when he is in a condition of being threatened by serious and/or imminent danger and of requiring immediate assistance.
Distress calls take priority over all other messages. As controller you shall acknowledge the distress call
ATC: [aircraft Call sign] Roger MAY DAY at time [hhmm]Z. When a MAYDAY is declared the aircraft requires an absolute priority service over all the other traffic.
Regarding the interaction ATC-crew, the same basic principles regarding the communications and instructions of an urgency call apply.
When appropriate, other aircraft operating in the vicinity of the aircraft in emergency should be advised of the circumstances.
When an emergency is declared by an aircraft, the ATS unit should take appropriate and relevant action as follows:
An aircraft known or believed to be in a state of emergency, including being subjected to unlawful interference shall be given priority over other aircraft.
ASSIST is a simple set of acronyms which may make it easier for controllers to remember the immediate actions, or sequence of actions, to be followed on initial notification in event of unusual/emergency situation:
Many organizations successfully adopted the ASSIST principle pioneered by the Deutsche Flugsicherung GmbH (DFS) entrusted for controlling the air traffic in Germany.
Upon receipt of advice that an aircraft is making an emergency descent through other traffic, all possible actions shall be taken immediately to safeguard all aircraft concerned.
The air traffic controller concerned shall inform any other air traffic controllers and control sectors which may be affected.
Immediately after such an emergency broadcast has been made, the approach control unit or the aerodrome control tower concerned shall forward further clearances to all aircraft involved as to additional procedures to be followed during and subsequent to the emergency descent.
When pilot initiates communication with ATC, a rapid response may be obtained by stating WEATHER DEVIATION REQUIRED to indicate that priority is desired on the frequency and for ATC response.
When necessary, the pilot shall upgrade the situation to the urgency status.
The pilot shall inform ATC when weather deviation is no longer required, or when a weather deviation has been completed and the aircraft has returned to its cleared route.
ATC should take one of the following actions: