" U.S. aviation safety experts say the shutdown of communications systems makes it clear
the missing Malaysia Airlines jet was taken over by someone who knew how the plane worked.
To turn off the transponder, someone in the cockpit would have to turn a knob with multiple selections to the "off" position while pressing down at the same time, said John Goglia, a former member of the U.S. National Transportation Safety Board. That's
something a pilot would know, but it could also be learned by someone who researched the plane on the Internet, he said.
The Aircraft Communications Addressing and Reporting System (ACARS) has two aspects, Goglia said. T
he information part of the system was shut down, but not the transmission part. In most planes, the information section can be shut down by hitting cockpit switches in sequence in order to get to a computer screen where an option must be selected using a keypad, said Goglia, an expert on aircraft maintenance.
That's also something a pilot would know how to do, but that could also be discovered through research, he said.
But to turn off the other transmission portion of the ACARS, it would be necessary to go to an electronics bay beneath the cockpit. That's something a pilot wouldn't normally know how to do, Goglia said. The Malaysia plane's ACARS transmitter continued to send out blips that were recorded by satellite once an hour for four to five hours after the transponder was turned off.
The blips don't contain any messages or data, but the satellite can tell in a very broad way what region the blips are coming from."
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