Riddle me this, pilots

The other day, I had an air traffic situation I wanted to bounce off of the
group. Those of you who don't know me, I'm a Center controller down here in
Atlanta. Here's the deal.

I was working a Center departure sector mixing Atlanta terminal departures
of every ilk and kin with enroute overflight traffic north of metro Atlanta.
The sector weather was typical summer MVFR down here- lots of convection,
hazy, hot, humid etc with building thunderstorms here and there impacting
the sector. I had received my briefing from the previous controller and had
just assumed responsibility for the airspace. Part of my technique is to do
one more quick traffic scan *after* I take over (while the previous
controller is still at hand) to ensure we didn't fumble a situation while we
changed the guard.

I am working a Baron IFR at 7000 flying from Chattanooga TN to Charleston
SC, on course heading of about 110 or so. Doing my scan, I see he has an
IFR off the nose about 15 miles at 6000 and another IFR guy crossing from
the NE at 8000 and 20 miles, so he is separated. I notice additional
traffic for this guy, a VFR indicating 6600 about six miles south, heading
about 055 or so, converging with him. I ask the previous controller if
she had issued traffic, she said she hadn't.

I made the traffic call.. "Baron 123, VFR traffic one to two o'clock, six
miles, northeast bound converging, altitude indicates six thousand six
hundred." The response I get is "Baron 123 is IMC, no contact."

I make a few unrelated routine calls to other traffic, keeping an eye on
this VFR target. His Mode C indicates that he is in a climb, and the
conflict alert activates (both data blocks begin to flash). I make another
call at four miles. "Baron 123, your traffic now two o'clock, four miles,
northeast bound, altitude indicating six thousand niner hundred VFR,
converging right to left." The Baron responds "123 is IMC, no contact."
The situation now has my undivided attention.

At three miles converging (next update), the traffic is indicating 7000.
The next update, the traffic is still at 7000. This guy is flying VFR where
one of my IFR's is IMC. I swing into alert mode. The target slashes are a
mile long each and the radar display is delayed a bit from actual position
so these guys are getting close and closing fast. The Baron needs to yank
it right most ricky tic and get behind this guy.

In the most professionally bored voice I can muster, I key up and say "Baron
123, traffic alert, traffic two o'clock, two miles converging from the right
indicating 7000, suggest you turn right heading 180 immediately." The Baron
pilot says "We're turning left to 090, no contact." I then watch as the
Baron swings into a left turn, prolonging the collision vector another
minute. His left turn away from the traffic puts him wing high with closing
traffic off the right side. The Baron also descends four hundred feet
during the maneuver as the targets merge. To me, this looks remarkably like
a TCAS maneuver because of the altitude change. I key up and say "N123, are
you TCAD equipped, do you have traffic avoidance avionics?" He gives me a
curt "Negative, we do not have the traffic." The targets have merged thanks
to the left turn, and I cannot distinguish the one from the other. Anything
I say now about the traffic would be a dangerous guess because I have lost
the flick between these two aircraft. Instead of responding to the Baron, I
issue a vector to the IFR traffic at 6000 to get him away from Baron 123
(who is now well below assigned IFR altitude). At the next position update,
I have tail to tail between the baron and the VFR. I tell the Baron,
"Traffic no factor, maintain 7000." He responds "We never saw him..." [The
unknown SOB in the VFR remains at 7000 for the next fifty miles- his profile
never changed and I have every reason to believe that he never saw the IFR,
IMC Baron].

My question for the group is about the Baron pilot's decision to disregard
my suggestion to yank it towards the traffic and instead to turn away from
him. From a controller's perspective, the quickest way to achieve "Oh Sh*t"
lateral separation with crossing traffic is to aim one airplane right at the
other. The idea is that as both aircraft are moving through space, the
maneuvering aircraft is steering for a point where the traffic *used* to be
but no longer is. Once the nose of the turning aircraft swings through his
traffic's vector, every additional second buys additional separation. When
we do this with IFR traffic, we call this a "Wimpy Crossover" or a "Bubba
Turn". If an aircraft turns away from conflicting crossing traffic, every
additional second of turn sees the targets get closer until either they
merge or else they *finally* get to the point of course divergence. The
closer the targets are when an away turn is initiated, the less effective an
"away" turn is.

Given this traffic scenario, would any of you guys have followed my
suggestion to turn to a 180 heading, or was I wasting my breath?

Chip, ZTL








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