Date:         10 Dec 97 04:05:04 
From: (Edward Hahn)
Organization: The MITRE Corporation
References:   1
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In article <airliners.1997.2868@ohare.Chicago.COM>, Andrew Weir <> wrote:
>Question 1: Is it true TCAS is required in US on passenger transports but
>not freighters? If it is good for one, why not the other?

This is correct, as the Congressional legislation mandating TCAS was worded to
protect air passengers.  The FAA (and Congress for that matter) is considering
a TCAS mandate for cargo carriers, but no decision has been made as of yet

In the US, the cargo airlines are considering alternate methods of collision
avoidance, using Automatic Dependent Surveillance-Broadcast (ADS-B).  The idea
is that each aircraft would periodically broadcast its position, speed,
heading, flight ID, and other information to everyone able to receive it.

In contrast, TCAS I/II uses active interrogations:  For example, if there are
ten aircraft in a volume of airspace, each aircraft must interrogate all of
the other aircraft, which then must reply to each interrogation individually,
to get the picture of the surrounding airspace.

Clearly, the ADS-B has the potential to reduce the amount of RF spectrum used
for this application.  In addition, ADS-B may have other applications which
could be used to increase the efficiency of the airspace system.

Obviously, there are many issues which to be worked out, including the
question of how one would get from today's TCAS environment to an ADS-B

BTW, you can read about the cargo airline's study at:


>>>>  Ed Hahn    |    |    (703) 883-5988  <<<<
The above statement is the opinion of the author.  No endorsement
or warranty by the MITRE Corporation is expressed or implied.
Really, I wouldn't kid you about a thing like this.