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Honeywell Aerospace, which supplied the emergency locator transmitters (ELTs) to Malaysia Airlines, said the device was not designed to function underwater. An ELT emits distress signals in the event of a crash on land or sea. The signals are tracked by satellites and help locate an aircraft. The International Civil Aviation Organisation (ICAO) norms make it mandatory for all aircraft on global flights to have ELTs.
Aviation safety experts have been perplexed why the Malaysia Airlines Boeing 777, missing for thirteen days and widely believed to have crashed, did not emit any signal. Cospas Sarsat, the global satellite system for search and rescue, too, has confirmed no signal was received from flight MH-370.
An aircraft's flight data recorder also has underwater locator beacons but these have range limitations. But the batteries help the beacons to run up to 30 days.
"The (ELT) system is activated by G-force caused by an impact. However, it is not designed or mandated to operate underwater,'' a Honeywell Aerospace spokesperson said. He added the system’s capabilities were designed in line with the norms by the Federal Aviation Administration Transport Canada and ICAO.
"We are not conducting our own inquiry or reviewing the system's performance. We are supporting the wider investigation of the incident as and when requested to do so,'' the spokesperson added. The ELT operates in a dormant state and cannot be switched off manually from the cockpit but can be activated manually, he said.
Aviation experts said ELT signals will turn weak in case of aircraft drowning.
"ELTs can be activated both by G-force impact and water. It is highly unlikely an ELT will not get activated on crash. I would only believe the Malaysian plane has landed somewhere in an undisclosed location,'' said aviation consultant Mark Martin.
However, the ex-joint director-general of civil aviation, Arun Chopra, said, "In a number of accidents, the ELT had not got activated, though the impact was such it should have. Usually the ELT or its antenna gets damaged in an accident or gets affected by fire; so, it does not transmit signals. A flight data recorder can withstand an impact.''
