Brazil 737-Embraer Crash

On Thu, 05 Oct 2006 09:22:08 -0500, James Robinson
wrote in :


TCAS only works with both transponders working.

Is the operating TCAS aboard the aircraft that is receiving a
transponder signal from another aircraft in its vicinity totally
incapable of outputting ANY useful information?

James Robinson writes:

TCAS only works with both transponders working. One was not working.

Are you sure? Even a TCAS-II system installed on a machine with an
inoperative transponder should still provide traffic alerting, no?

- FChE

(Let me try to make my question a little clearer.)

On Thu, 05 Oct 2006 09:22:08 -0500, James Robinson
wrote in :


TCAS only works with both transponders working.

Is the operating TCAS aboard the aircraft that is receiving a
transponder signal from another aircraft in its vicinity totally
incapable of outputting ANY useful information when it's transponder
is not operating?

YOU........don't know that!



"James Robinson" wrote in message
. ..
Kevin Clarke wrote:

Then of course I am really scratching my head about 2 TCAS "failures" or
at least TCAS being ignored. Sad.

TCAS only works with both transponders working. One was not working.

http://www.nytimes.com/2006/10/03/bu...ewanted=2&_r=1

"karl gruber" wrote in message
...
YOU........don't know that!



"James Robinson" wrote in message
. ..
Kevin Clarke wrote:

Then of course I am really scratching my head about 2 TCAS "failures" or
at least TCAS being ignored. Sad.

TCAS only works with both transponders working. One was not working.

(Frank Ch. Eigler) wrote:


James Robinson writes:

TCAS only works with both transponders working. One was not working.

Are you sure? Even a TCAS-II system installed on a machine with an
inoperative transponder should still provide traffic alerting, no?

Not as I understand it. Here are some quotes from an ARINC description
of TCAS-II:

"A Mode S transponder is required to be
installed and operational for TCAS II to be
operational. If the Mode S transponder fails,
the TCAS Performance Monitor will detect
this failure and automatically place TCAS
into Standby."

"TCAS does not alter or diminish the pilot’s
basic authority and responsibility to ensure
safe flight. Because TCAS does not respond
to aircraft that are not transponder-equipped
or aircraft with a transponder failure, TCAS
alone does not ensure safe separation in
every case."

"karl gruber" wrote:

"James Robinson" wrote:

Kevin Clarke wrote:

Then of course I am really scratching my head about 2 TCAS
"failures" or at least TCAS being ignored. Sad.

TCAS only works with both transponders working. One was not working.

YOU........don't know that!

Quite right. I don't personally know whether the transponder was working
or not.

I should have said that it was reported to have ceased transmitting before
the collision, and started transmitting again after the collision. This
was part of a statement from a Brazilian Air Force representative in a news
conference. The BAF is heading the investigation into the accident. It was
one of the reasons given for holding the passports of the US pilots.

Recently, Larry Dighera posted:

(Let me try to make my question a little clearer.)

On Thu, 05 Oct 2006 09:22:08 -0500, James Robinson
wrote in :


TCAS only works with both transponders working.

Is the operating TCAS aboard the aircraft that is receiving a
transponder signal from another aircraft in its vicinity totally
incapable of outputting ANY useful information when it's transponder
is not operating?

As I understand it, it is the transponder signal of other aircraft that
TCAS reports. If other aircraft in the area either don't have a
transponder or it is inoperative, there is nothing for the TCAS to lock
onto, ergo, no useful information about traffic position.

Neil

On Thu, 5 Oct 2006 10:28:46 -0700, "news.charter.net"
wrote in
:

http://www.nytimes.com/2006/10/03/bu...ewanted=2&_r=1

Thanks for the link to the New York Times story (even if I did have to
use bugmenot.com to access it). Unfortunately it doesn't mention the
TCAS system which was the subject of the article to which you were
following up. But it did contain this nugget:

A Brazilian military inspector standing by surprised me by his
willingness to talk, although the conversation was limited by his
weak English and my nonexistent Portuguese.

He was speculating on what happened, but this is what he said:
Both planes were, inexplicably, at the same altitude in the same
space in the sky. The southeast-bound 737 pilots spotted our
Legacy 600, which was flying northwest to Manaus, and made a
frantic evasive bank. The 737 wing, swooping into the space
between our wing and the high tail, clipped us twice, and the
bigger plane then went into its death spiral.

It sounded like an impossible situation, the inspector
acknowledged. “But I think this happened,” he said. Though no one
can say for certain yet how the accident occurred, three other
Brazilian officers told me they had been informed that both planes
were at the same altitude.

On Thu, 05 Oct 2006 12:32:31 -0500, James Robinson
wrote in :

(Frank Ch. Eigler) wrote:


James Robinson writes:

TCAS only works with both transponders working. One was not working.

Are you sure? Even a TCAS-II system installed on a machine with an
inoperative transponder should still provide traffic alerting, no?

Not as I understand it. Here are some quotes from an ARINC description
of TCAS-II:

"A Mode S transponder is required to be
installed and operational for TCAS II to be
operational. If the Mode S transponder fails,
the TCAS Performance Monitor will detect
this failure and automatically place TCAS
into Standby."

The Mode S requirement is suspect, as I have had jet aircraft indicate
that they could see me on their TCAS units while the transponder
installed in the aircraft I was operating was not even squawking Mode
C, but it was squawking.

"TCAS does not alter or diminish the pilot’s
basic authority and responsibility to ensure
safe flight. Because TCAS does not respond
to aircraft that are not transponder-equipped
or aircraft with a transponder failure, TCAS
alone does not ensure safe separation in
every case."

That statement does not support your assertion, that both aircraft
must have transponders operating for TCAS to provide avoidance
information.

I would guess, that if the transponder in a TCAS equipped aircraft
were turned off, the TCAS unit in that aircraft would still provide
information about other transponder equipped (and squawking) aircraft
in the area, but that wouldn't do those aircraft with operational
transponders any good unless the pilot receiving the TCAS information
took evasive action.