Ntsb Advisory Regarding Communications Involving Us Air Flt 1549
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NTSB ADVISORY
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National Transportation Safety Board
Washington, DC 20594
February 6, 2009
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NTSB DETAILS TYPES OF COMMUNICATIONS INVOLVING US AIRWAYS
FLIGHT 1549
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Due to the intense interest in the recorded communications
between the pilot of the US Airways aircraft that ditched
into the Hudson River on January 15 of this year, and air
traffic control, the NTSB has provided a brief explanation
of what these communications entail, as well as the
difference between the air traffic control (ATC) recording
and that of the cockpit voice recorder (CVR).
The ATC recordings capture the radio transmissions between
air traffic controllers and pilots on a specific radio
frequency reserved for use in aeronautical communications.
ATC transmissions are carried over the public airways and
can be monitored in real time by anyone with a radio tuned
to the appropriate frequency.
The ATC recording primarily captures two types of
communications: 1) the radio transmissions between the air
traffic controllers and pilots of the numerous aircraft on
that frequency, and 2) communications by air traffic
controllers made by radio, phone or other direct electronic
audio link to other ATC facilities.
In the case of the ATC recordings related to the ditching of
US Airways flight 1549, which were released by the Federal
Aviation Administration (FAA) this week, the controller at
the New York TRACON LaGuardia Departure facility
communicated with a total of 14 entities - aircraft and
other controllers at ATC facilities - all of which were
recorded.
The recording captured by the cockpit voice recorder (CVR)
is different from that of the ATC recording. Whereas the
bulk of the ATC recording captures the radio transmissions
between air traffic controllers and pilots, the CVR, by way
of a microphone mounted on the overhead instrument panel and
microphones in the headsets worn by the pilots, records all
of the sounds inside the cockpit, including the
communications with ATC.
In addition to recording all conversations between the
pilots themselves and between the pilots and ground and
cabin crew, the CVR captures sounds such as engine noise,
automated warnings, landing gear extension and retraction,
and other sounds that may yield information on the functions
being performed inside the cockpit as well as those related
to the operation of the aircraft.
A CVR committee, usually consisting of members from the
NTSB, FAA, operator of the aircraft, manufacturer of the
airplane, manufacturer of the engines, and the pilots union,
is formed to listen to the recording. This committee creates
a written transcript of the CVR audio to be used during the
investigation. This transcript is released by the NTSB
either at the time of a public hearing, or if there is no
hearing, at the time the accident docket is opened to the
public. The timeline for either of these events is usually
six months or more into the investigation. In the United
States, the actual CVR audio recording is protected by law
and is never released to the public.
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NTSB Media Contact: Peter Knudson, (202) 314-6100
[email protected]
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