Peter Duniho wrote:

wrote in message ...
[...] it
seems that the air traffic procedures folks are primarily fooling
themselves
(so, what's new? ;-) when they don't consider an unknown secondary target
returning Mode C data to be sufficiently radar identified for merging
target
safety action.

Keep in mind that if ATC is not in radio communications with the radar
target, they have no way to verify the Mode C readout. As such, it should
be considered unreliable. Since an ATC instruction could include an
altitude change instead of or in addition to a heading change, the rules
need to account for that.

That is exactly what a TCAS RA does, and it relies on "unverified" Mode C.
But, a merging target vector should not include an altitude change unless the
controller has the altitude available, and then only as a last resort to an
avoidance vector.



My personal opinion is that, generally speaking, the FAA folks who come up
with ATC procedures do have a clue, and the procedures mostly make sense.

Good thing TCAS isn't so strict about what it tags.

I guess that's a matter of debate. A faulty Mode C readout could cause a
TCAS unit to cause an accident, rather than avoid one.

Well, so far it has only prevented accidents. Had it been used properly on the
Swiss border, a lot of folks would still be alive today..