(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."