Malaysia Flight 370: Amid a sea of questions, 30 of the most compelling

Malaysia Flight 370: Amid a sea of questions, 30 of the most compelling





11. What is ACARS?
Introduced in 1978, the
air/ground data system was initially used by airlines to record and
report basic aircraft movement messages, according to Rockwell Collins,
which sells avionics and communications systems to aviation customers.
In 1989, ACARS's use was expanded to include air traffic service
communications. It uses three radio frequency paths for delivery: two
ground-based satellite systems (VHF and UHF) and a satellite link
(SATCOM) to send and receive information.
"It's a system where you
send digital communications from ship to ground," said John Testrake, a
pilot for American Airlines with more than 20 years' experience flying.
The automated system generally sends routine messages to the airline,
like when the aircraft lifted off or landed and how much fuel it may
have, he said. It can also be used to communicate text messages like
"light continuous turbulence over the Rockies south of Denver," he said.
"You might want to send
that report to your dispatcher so they can give a heads up to the next
flight that's coming into that area."
Tom Haueter, former
director of the National Transportation Safety Board's Office of
Aviation Safety, said ACARS typically beams down engine parameters,
temperatures, the amount of fuel burn and any maintenance discrepancies.
According to Malaysia Airlines,
all of its aircraft are equipped with ACARS, which transmits data
automatically. "Nevertheless, there were no distress calls, and no
information was relayed," the airline said.