On Tue, 10 Feb 2004 19:27:31 -0500, "Calergin"
wrote:

I hope you dont mind some info here. I happen to have a little experience
with TCAS and how it works.

snip

One big issue for the TCAS is the fact that a large population of aircraft
owners are not maintaining their Mode C encoders and having them check every
2 years. Encoders have been found to be off by as much as 1000 or more
feet. If you are flying at 1500 feet and your encoder says you are at 2200
feet and the TCAS equipt aircraft is at 2000 feet guess who will be
decending to avoid a target at 2200 feet. Guess who will be in for a big
surprise if they get to 1500 feet.

I hope that helps.
If you go to http://www.arinc.com/tcas/ and download
Introduction to TCAS II 7.0 you will have a good grasp of TCAS
priciples of operation.

Mike Borgelt