The only time this would really be an issue would be if the other aircraft
were on an exact reciprocal course. And even if he used a corresponding
offset, he would still be 1,000 feet above or below you...



"Icebound" wrote in message
...

"Bill Denton" wrote in message
...
I noticed the later posts referenced a set of "rules" for setting up the
"error", but absent those, you are back to the same old game of chance.
What's to prevent another pilot from picking a corresponding "error"
that
would still maintain the head-on courses?


Well, if *I* were choosing a *parallel offset*, it would always be to the
*right* of direct-track. Maybe the guy on the reciprocal track would
think
to do the same.


And I don't know if this is a trick question, but if you are at 6000 (no
+500) wouldn't you be on an IFR flight plan, talking to ATC, and
receiving
traffic advisories?

Well, I don't do IFR, but if you wish, change the scenario to my westbound
Cessna at 6500. And we are all "looking out", but just at the time we
appear as dots in each others windshield, my wife drops a water bottle
that
rolls under my feet, so I bend down to get it, and she watches me. He's
been in the cockpit for 3 hours, in cruise descent, and his kid in the
back
seat is a little antsy, and he's just realized he needs to look up a
frequency in the Airports and Frequency guide, because its kind of smudged
on his chart; he didn't think he'd need it, but what the hell.

The question was not meant to be tricky, nor to suggest that I am going to
throw my A/P onto the GPS and read the newspaper, instead of looking out
the
window. I am just wondering out loud if super-accurate GPS nav creates a
"reduced chance" of horizontal clearance, over previous nav methods, given
the usual weaknesses and foibles of human pilots.






"Icebound" wrote in message
...
In the "good old" VOR days, it must have been pretty difficult to fly
down
the centerline of an airway (or of any direct track).

So an eastbound VFR/IFR aircraft descending from 7500/7000 to his
destination, was more than likely to avoid traffic... on the reciprocal
track passing him by at 6500 or 6000... by some significant horizontal
error-distance, even if they didn't see each other (big sky theory
:-) ).

GPS horizontal accuracy with WAAS is already in the order of magnitude
of
a
Cessna's wingspan, and some are talking about getting it down to mere
inches.

So the question is: If my Westbound Cessna at 6000 feet (with the
autopilot
keeping it happily on the GPS-track centerline) meets the descending
Bonanza
on the reciprocal track between the same two airports (using a similar
GPS/a-p combo), there is a distinct possibility that the horizontal
clearance may be zero...

...so is there anything in the current crop of GPS and/or Autopilot
systems
that allow me to maintain a small cross-track error of my choosing,
without
actually entering off-navaid-off-airport waypoints? ...or do we care;
am
I
overly concerned???