Communications satellites picked up faint electronic pulses from Malaysia
Airlines Flight 370 after it went missing on Saturday, but the
signals gave no information about where the stray jet was
heading and little else about its fate, two sources close to the
investigation said on Thursday.
But the "pings" indicated that the aircraft's maintenance
troubleshooting systems were switched on and ready to
communicate with satellites, showing the aircraft, with 239
people on board, was at least capable of communicating after it
lost touch with Malaysian air traffic controllers.
The system transmits such pings about once an hour,
according to the sources, who said five or six were heard.
However, the pings alone are not proof that the plane was in the
air or on the ground, the sources said.
While the troubleshooting systems were functioning, no data
links were opened, the sources said, because the companies
involved had not subscribed to that level of service from the
satellite operator.
Boeing Co, which made the missing 777 airliner, and
Rolls-Royce, which supplied its Trent engines, declined to
comment.
Earlier Malaysian officials denied reports that the aircraft
had continued to send technical data and said there was no
evidence that it flew for hours after losing contact with air
traffic controllers early Saturday after taking off from Kuala
Lumpur en route to Beijing.
The Wall Street Journal had reported that U.S. aviation
investigators and national security officials believed the
Boeing 777 flew for a total of five hours, based on data
automatically downloaded and sent to the ground from its engines
as part of a standard monitoring program.
Sources familiar with the investigation reiterated that
neither Boeing nor Rolls-Royce had received any engine
maintenance data from the jet after the point at which its
pilots last made contact.
There is still no evidence that demonstrates the plane's
disappearance five days ago was related to foul play, U.S.
security sources stressed, though the officials said they still
have not ruled out the possibility of terrorism.
ACARS MESSAGING
Modern aircraft can communicate with airline operations
bases and sometimes with the headquarters of its manufacturers
automatically to send maintenance alerts known as ACARS
messages. It was this system that sent out the hourly pings,
apparently over several hours, the sources said.
But Malaysia Airlines had not signed up for an expanded
service that is based on the system and can send information
such as updated flight plans and position reports, people
familiar with the matter told Reuters this week, .
In the past such data was sent via radio links, but in
recent years, airlines have begun using satellites to transmit
the information more reliably.
Oliver McGee, a former senior U.S. Transportation Department
official and professor of mechanical engineering at Howard
University in Washington, said the pings by themselves would not
necessarily help locate the plane. Data about the engine's fuel
burn, weight and other aspects of its performance is needed to
help determine how far the airplane had traveled, he said.
"It depends on the data coming from the engines," McGee
said. "If you have no reliable source of what information you
are reading, you can not get the range, air speed or time
traveled."
He cautioned that the aircraft could continue to generate
the signals, even if it had crashed, depending on any damage to
the aircraft and its engines.
Mark Rosenker, a former chairman of the National
Transportation Safety Board, said the aircraft would continue
generating the signals even if it was on the ground, unless the
system had shut down.
Honeywell International Inc makes the components that go
into the ACARS system on Boeing 777s, but a different service
provider sets them up to communicate with the airlines, said one
industry source familiar with the system.
Each airline determines how it wants the system to work and
under what circumstances, said the source, noting that some
carriers receive messages when the plane is using auxiliary
power, while others want updates only when the aircraft's
engines are running.
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