SAR Direction Finders for Airborne Rescue Missions
Every country that is involved in international air traffic is obliged to operate an SAR service.
Today, virtually all aircraft are equipped with ELTs (Emergency Locator Transmitter ), which automatically transmit an emergency signal that can be received by other aircraft and satellites in the event of a distress incident. By using satellite data and the last known radar position, it is possible to determine the approximate location of the incident and initiate SAR activities. In general, the search is carried out by helicopter or winged aircraft.
Here too, localization of the downed aircraft and the passengers represents the greatest difficulty. In many cases, when an aircraft comes down in a wooded area, for example, it may be hardly visible or not visible at all.
In addition to the conventional emergency signals (121.500 and 243.000 MHz), modern emergency beacons also transmit a digital message to the Cospas-Sarsat satellites (406.028 MHz). The conventional emergency signals are transmitted without interruption but are relatively weak since the output power is approximately 100 milliwatts. However, the Cospas-Sarsat signal is a 300-millisecond digital pulse that is transmitted only every 50 seconds, and the output power is 5 to 7 watts.
The RT-600 (SAR-DF 517) SAR direction finder system can receive, display and localize extremely remote signals. This makes it possible to head in the direction of the vessel, aircraft or person in distress. Once the SAR aircraft is close enough to be able to receive the continuously transmitted emergency signals, the direction finder system automatically switches to either the 121.500 MHz or 243.000 MHz frequency to home in on the site. Overflight is clearly indicated to permit precise localization of the emergency beacon. Channel 16 of the marine radio band is also available.
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