When a pilot or crew encounters an emergency or distress situation they can simply call for assistance by contacting ATC or any other agency responsible for the area they are flying over. They will need to state their difficulty, express their intentions and if any assistance is required to handle the situation.
To do this efficiently they must have all the required information, frequencies and radio procedures, at hand as is required during preflight.
For this communication to proceed orderly the International Civil Aviation Organization (ICAO) has developed or prescribed standard procedures. This will help communicating the much needed information in a timely manner and alert others on the same frequency.
For efficient and quick emergency communications there are a number procedures and items the pilot must be familiar with.
Aircraft crew should start their distress communication with an internationally recognized phrase: MAYDAY. This phrase commands radio silence on the frequency from other aircraft and this type of communication has the highest priority. Urgency communications are preceded by the words PAN-PAN and they have priority over all other communications except distress.
At the same time the aircraft transponder should be set accordingly: Mode A/C/S and code 7700 for emergency if you were not flying with an assigned code. Other preset transponder codes are available for radio loss or hijack situations. Read our article on transponder codes for more information about those.
Distress or urgency communications will be address to the ATC or agency the flight crew is in contact with. Should there be no response the call may be addressed as a broadcast and should start with: "Any station". In this case anyone receiving the call may respond to this when able to.
The receiving station should acknowledge the call and provide assistance, coordinate and alert the appropriate facilities and possible rescue coordinator.
All other stations on the frequency will continue to listen until assistance is being provided. If it becomes apparent that the station being called has not or is unable to receive the distress or urgency call any station may attempt to contact the aircraft and provide assistance, for example by relaying messages to an ATC unit.
Normally the frequency in use or another frequency assigned by ATC is preferable but there are a number of frequencies available for urgency or distress communications if so desired.
In the VHF (Very High Frequency, 30 - 300 MHz) band 121.5 MHz and 234 MHz are available for these communications. These frequencies are guarded by tower, flight service stations, radar facilities and military aircraft. Range is limited to VHF line of sight, so flying high increases range and your chance of being heard.
Longer range communications are available on the HF band (3 - 30 MHz) and the assigned emergency frequency is 2128 kHz / Upper Side Band modulation in the high MF band (300 kHz - 3 MHz). This frequency is guarded by Coast Guard Rescue Coordination Centers, commercial coast station and even ocean going vessels.
Should nobody respond on these frequencies, call the nearest tower or area FCC.
An aircraft in urgency or distress should follow the next procedures: Climb, if possible and allowed under IFR, to improve radio communication range. Continue to squawk the assigned transponder code or switch on the transponder beacon on Mode A/C/S 7700 emergency mode, and transmit your distress or urgency message:
In a later message the aircraft status should be transmitted: weather, fuel on board, number of souls, ELT availability, emergency equipment and any other useful required information.
With the new 406 ELTs being able to transmit your GSP position it can be helpful to switch the ELT on just before an emergency landing.
Should a water landing be eminent try to do so near a surface vessel, make sure everyone has their life vest on and any door is cracked open just before ditching. In a low wind situation ditch parallel to the swells, best position is on top of the swell.