Inside GNSS Media & Research

MAY-JUN 2018

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Page 32 of 67 M A Y / J U N E 2 0 1 8 Inside GNSS 33 manually to transmit a distress signal at 406 MHz for at least 24 hours. For flights AF447 and MH370, no alert messages transmitted by the ELT were received. e reasons are still unknown but sev- eral hypotheses can be formulated: the transmission system was damaged at the impact and transmission could not occur, or the wreck and the distress bea- con sank very quickly before the beacon could transmit its first distress message. Without the alert messages, no informa- tion independent of the aircra systems was available to determine the position of the crash for both the AF447 and the MH370 aer all the aircra equip- ment failed. To prevent this situation from occurring again in the future, the solution would be to be able to receive information about the location of the aircraft during the in-f light distress phase. Based on this, ICAO and the international aeronautical community carried on activities to reconsider the effectiveness of the existing SAR opera- tions by improving the in-flight tracking of the aircras during the entire flight and under all circumstances, including normal flight and distress. e activities of the Ad-hoc Working Group on Air- cra Tracking led to the definition of a Global Aeronautical Distress and Safety System (GADSS) and additional amend- ments to the ICAO Annex 6 divided into 3 functions ( Figure 1 ): • Aircra Tracking (AT): transmission of data of time and position or infor- mation to determine the position of the aircra at least every 15 minutes during normal flight phase • Autonomous Dist ress Track i ng (ADT): transmission of time and position or information to determine position of the aircra at least every minute during in-flight detected dis- tress phase • Post Flight Localization and Recov- ery (PFLR): localization of flight data recorders thanks to beacons associ- ated to the FDR. The ADT function requirement is the answer to the AF447 and the MH370 accidents and its necessity has been con- firmed by other aeronautical accidents (like the Egyptair MS804): by initiating the tracking of the aircra during in- flight distress phase and with the avail- ability of transmitting accurate time and position data, the probability to receive a distress message is increased, as well as the accuracy of the location of the crash area. e evolution of the Cospas- Sarsat system, mandatory onboard all commercial aircra, into an ADT sys- tem appeared as an appropriate solution and is further described in the following sections. Cospas-Sarsat Solution to ADT Recommendations a. The Cospas-Sarsat program The International Cospas-Sarsat Pro- gram provides accurate, timely and reliable distress alert and location data to help SAR authorities assist persons in distress. e objective of the Cospas- Sarsat system is to reduce, as much as possible, delays in the provision of dis- tress alerts to SAR services, and the time required locating a distress and pro- viding assistance, which have a direct impact on the probability of survival of the person in distress at sea or on land. To achieve this objective, Cospas-Sarsat Participant governments and agencies implement, maintain, coordinate and operate a satellite system capable of detecting distress alert transmissions from radio-beacons that comply with sages transmitted by the Cospas-Sarsat Emergency Locator Transmitters (ELT) distress beacons (mandatory on-board any commercial aircra by Internation- al Civil Aviation Organization [ICAO] requirements) were received by the SAR ground segment. e current ELTs are designed to be triggered automatically further to a shock or upon activation by water (typically aer a crash or a hard landing on ground or into the ocean) or GADSS-Concept of Operations V6.0 FIGURE 1 High level overview of the GADSS and its functions

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