The focus of search efforts shifted on Thursday from the South China Sea after the US said new information indicated that Malaysia Airlines Flight MH370 may have gone down to the west in the Indian Ocean. China, which had more than 150 citizens on board the missing plane, today said the confirmation foul play was involved in the flights disappearance was painfully belated. The Boeing 777 has one of the best safety records of any commercial aircraft in service. Its only previous fatal crash came on July 6 last year when Asiana Airlines Flight 214 struck a sea wall with its undercarriage on landing in San Francisco. Three people died in the incident. THREE TYPES OF SIGNALS GIVEN OFF BY PLANES, AND HOW THEY RELATE TO MISSING MH370 The missing Malaysia Airlines Boeing 777-200 sent signals to a satellite for four hours after the aircraft went missing, an indication that it was still flying for hundreds of miles or more, according to a U.S. official briefed on the search for the jet. This raises the possibility that the plane may have flown far from the current search areas. Here is a look at three types of signals planes give off, and how they relate to the missing jetliner: TRANSPONDERS Transponders are electronic devices that automatically identify commercial aircraft within air traffic control radar range and transmit information on the planes identity, location and altitude to ground radar stations. Beyond radar range, they enable planes to be identified and tracked anywhere in the world by satellite. Transponders can be turned off by pilots. The missing jets transponder last communicated with Malaysian civilian radar about an hour after takeoff, when the plane was above the Gulf of Thailand between Malaysia and southern Vietnam. ACARS ACARS - or Aircraft Communications Addressing and Reporting System - is a data link system used to transmit short messages such as weather updates and status reports between aircraft and ground stations via radio or satellite. According to the U.S. official, ACARS messages sent by the missing plane continued after its transponder went silent, although he wasnt certain for how long. OPERATING DATA SENT VIA SATELLITE Boeing offers a satellite service that can receive data during a flight on how the aircraft is functioning and relay the information to the planes home base. The idea is to provide information before the plane lands on whether maintenance work or repairs are needed. Even if an airline does not subscribe to the service, planes still periodically send automated signals - or pings - to the satellite seeking to establish contact. Malaysia Airlines did not subscribe to the satellite service. The U.S. official said automated pings were received from the jetliner for four hours after it went missing, indicating it probably flew for hundreds of miles beyond its last confirmed sighting on radar.
Posted on: Sun, 16 Mar 2014 12:22:00 +0000
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