Riddle me this, pilots

Or if a mid-air was inevitable, any turn would have prevented it.

Big problem is autopilot no clearance in IMC.

Still beats driving on a two-lane road.

H.
N502TB
"Big John" wrote in message
...
Chip

Look at it this way. If he had had a mid air then you would have been
exonerated.

Big John


On Mon, 18 Aug 2003 22:12:19 -0400, "Chip Jones"
wrote:


"David Corsi" wrote in message
news:Ize0b.146544$cF.53272@rwcrnsc53...
the thing I don't understand is if he is IMC why would he decide to
turn a
different direction from the ATC directed one? i too would guess a TCAD
manuever based on azimuth data but I somehow doubt that was the case
really.
i just don't understand the logic, did he just mishear the heading
assigned
or did you repeat the 180 degree heading when he responded 90?


When he responded that he was turning left, I didn't repeat my suggestion
to
turn right. I don't know if he misheard me, but I did tell him both the
direction and azimuth of the suggested turn in my alert which would make
it
harder to misunderstand IMO. I didn't repeat the vector suggestion
because
in my mind he was countermanding my suggestion by excercising his PIC
authority. To me, he was on scene while I was looking at things through
a
long range filter. He also acted decisively without hesitation even if I
think he went the wrong way. Too many unknowns between my alert
/suggested
vector and his response / maneuver to allow me to comfortably restate my
suggestion.

Chip, ZTL




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"Ben Jackson" wrote in message
news:EQf0b.149627$Oz4.41062@rwcrnsc54...
In article ,
Chip Jones wrote:

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."

Why did it get that far?

First of all, I had about fifteen airplanes on frequency. Mentally I was
gearing up for the wad of Atlanta departures that were getting ready to
launch (indeed were beginning to check on freq) and how the weather was
going to impact the departure push. I also had other IFR irons in the fire.
For example, I had two IFR's inbound to JZP and I was blocking for an
approach at 47A (which conflicts with JZP). I was mentally trying to get a
plan working for sequence into JZP while I was making that final
position-relief traffic scan. To me, the VFR target represented a very low
priority traffic call at six miles and 400 feet, especially since I don't
have separation responsibility between IFR and VFR traffic in thsi airspace.
I *do* have an air safety obligation that trumps all of my separation
responsibilities, but at six miles, and even at four miles, I did not
recognize that this situation was going to deteriorate from a routine
traffic situation into an alert situation with co-altitude traffic.

If I'm the Baron I'm thinking, "I can't see
the traffic, I won't see the traffic in IMC, why is this guy waiting
for me to spot this plane?"

I suppose he could have requested a vector at the first or second call. I
was waitng for him to spot the traffic because that's what happens between
VFR and IFR traffic in this airspace. See and avoid.

If you *believed* that he was really in
the soup, why not just pretend the VFR target was a lost-comms IFR
guy and gotten the Baron out of the way?

I didn't believe that the VFR was in the soup until he got co-altitude with
the IFR guy who had reported twice that he was IMC at 7000. I see an
unknown VFR target, I assume the pilot is complying with FAR's. In this
case, I can't prove that he wasn't.


Plus if two aircraft are 2 miles apart and you turn one 90 degrees,
by the time the turn is completed they will have both covered a mile.
My mental image of this is that you're turning a situation where the
two course lines would converge to a sharp point into a situation
where they would converge in a nice rounded corner.


I disagree with you here. I do not use the phraseology "immediately" unless
I am worried about an imminent collision. In 13 years of ATC, I have used
"immediately" probably less than twenty times. In order for the baron to
slip behind the VFR, he did not need to turn 90 degrees, he only needed to
turn 45 to 50 degrees right. I assumed that combining "immediately" with a
suggested 80 degree right turn, there was the highest probability of a
successful outcome for the Baron. In the event, the left turn of 20 or 30
degrees that the Baron pilot executed in the event was insufficient to keep
his target from merging with the intruder.

Chip, ZTL





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I've read all the other comments posted so far.. pretty much a 50/50 split
in options..

As an IFR pilot, my first reaction would be to take the ATC suggested turn
I'm IFR so the bozo must be too, but "Monday morning" says to initially turn
away from the traffic.. not towards, at the 2 O'clock and 2 mile call, based
on the turning radius of the Baron at 180knts TAS plus, the turn away would
give him a little more free distance before possible collision and more time
to loose a little altitude. And based on the Baron's speed being a tad
faster than the Cessna Spam Can variety aircraft, the extra speed may pull
you out in front.

Turning into the traffic (point your nose at his tail, you'll miss 'em
theory), based on the turning radius, may put the two together sooner,
allowing less time to apply an altitude change to the solution.

If you delay the turn to late, the turning radius will kill the plan.

BT (former ZBOS)

"Chip Jones" wrote in message
...
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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"Roy Smith" wrote in message
...
"Chip Jones" wrote:
Here's the deal.

An interesting choice of words :-)

Ya well, as we say in Class E between IFR's and VFR's, "no dent, no deal".


Hard to say for sure, but I can offer a few insights from my own
experiences. As a general rule, if the controller says, "immediately",
I put my life in his hands, follow orders, and ask questions later.

I've only once heard the phrase "traffic alert". I was IFR, the
controller was not talking to the other guy. It was not solid IMC, but
there was plenty of IMC around. I can only guess the other guy was not
legal VFR.

I don't routinely have to issue traffic alerts either. Usually this sort of
call eventually results in "traffic in sight, thanks Center".



In this case, the controller did not issue a suggested heading. My
response was to turn 90 degrees away from the direction the traffic was
being called. I can certainly see your point where turning directly
into the traffic would have put me behind him, but that wasn't my
instinctive reaction.

I agree it is counter intuitive, and no matter what the controller is safely
on the ground regardless of where the pilot ends up. Not trying to be
cynical, either.


I suspect your traffic call may have been by the book, but on the other
hand, it was probably too verbose to really be useful to the pilot. I'm
guessing that with each successive traffic call leading up to the alert,
the pilot was getting increasingly antsy about the unseen traffic, and
already working out an escape plan -- "bad stuff to the right, I gotta
get left, away from the danger". All it took was hearing the words
"traffic alert" to trigger that plan into action.

Thanks for the insight Roy- I follow you.


I just timed how long it took me to calmly read the above clearance.
Seven seconds between "traffic alert" and "heading 180". At standard
rate, the guy's already 20 degrees into his left turn before he knows
you want him to turn right (and I'm not sure I would limit myself to
standard rate in response to a traffic alert).

I'm betting that's exactly how it went down. I did not observe the Baron's
maneuver until well after it began, so I can't really judge when it began.
I didn't even catch the altitude bust until a couple of updates later.
You're right, he was probably ready to execute a maneuver as soon as he got
the TA.

More than the physics of
changing heading, consider the human factors -- he's already made a
decision and acted on it. He's already made the mental leap from
obeying instructions to acting on his own. It's not going to be easy to
get him back into the fold quickly.

Well the PIC was definitely decisive in the event. He didn't bandy any
words, and it was clear that he was set on the left turn because he didn't
hesitate one instant when he told me he was turning left.


My guess is, by-the-book or not, a better way to say it might have been,
"Barron 123, traffic alert, immediate left turn, heading 180". Get it
right up front what you want the guy to do.


That's good advice. I'll put that in the bag of tricks.


I fully understand the reason the book wants the phrasing the way it
does. It's the PIC's decision, and the controller is just feeding the
PIC information which will let the PIC make an informed decision. The
problem is, I don't think it works that way in real life. It's hard
enough working CPA problems (Closest Point of Approach; do they call it
that in the ATC world?) looking at a screen or a plotting sheet. It's
damn near impossible in your head with nothing better than an O'Clock
traffic call, some dubious WCA, an unknown speed and cardinal heading on
the target, and no formal training.

I can't even imagine. We don't call it CPA. We call it Point of
Convergence down here. Dunno if that is FAA standard.


PIC-correctness, legality, and liability issues aside, the fact is the
controller is the one with the best picture of what's going on, and it
makes the most sense for the controller to take charge and issue an
unambigious instruction, with no extraneous information to get in the
way of communicating the one thing you really want to communicate: which
way to turn.

No doubt about that. I will point out that when I suggest something on
frequency like in this event, I do use the command voice. I don't hesitate
on the radio when I am working airplanes. The only difference in my
transmission between a suggestion and an instruction is the word "suggest".
Otherwise I try to make it sound calm but imperitive.


It's a pity there's no mechanism to plan stuff like this a little
further in advance. At the 5-mile point, it would be nice if I could
hear, "Hold current heading for now. If you don't see him in another 3
miles, I'm going to turn you left to pass behind him". Does "the book"
allow for such a conversation?

If you ask for it, certainly. And I have been known to issue timely ATC
instructions to IFR aircraft to avoid VFR aircraft in Class E, which is
stretching the rules but can be justified as "good judgement". I find it
easier to do this between a known VFR and IFR rather than between an IFR and
an unknown intruder.

In the actual event though, I did not recognize that this particular
situation was developing into a close call until after it was going down.


[snipped]


Think about what was going on from the pilot's perspective. You kept
telling him, "Something bad might be happening soon. I know the best
way to deal with it, but I won't tell you what it is yet. Don't worry,
though, at the last possible second I'll clue you in on the plan and
then expect you to react immediately".

Well, I can see how the pilot could have that perspective. However, I
truely didn't know the best way to deal with it (south vector) until about
four miles because the VFR was maneuvering vertically according to his mode
C. I was banking that the VFR and the IFR would see and avoid if I only
gave the IFR a few good traffic calls. (Wrong!) This event occurred on a
Sunday around 1300L in Class E about 50 miles NE of ATL. This airspace sees
an awful lot of unknown VFR's because it is convenient to the Atlanta
terminal area, is outside of Tracon airspace (and the Class B rings) and is
a good place for the various flights schools at the satellite fields like
RYY, LZU, 47A and PDK to conduct flight training without getting a KingAir
or Citation enema. (You can't swing a dead cat inside the terminal area
without hitting a VFR target on a Sunday afternoon). I could have vectored
the Baron early "for traffic" only to have this unknown VFR swing back
around towards Atlanta and right at him or something.


Well, anyway, that's my take on it. Other people will probably have
different opinions.

No doubt, but as always I do appreciate your take.

Chip, ZTL




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"Capt. Doug" wrote in message
...
Chip Jones wrote in message The response I get is "Baron 123 is IMC, no
contact."

Howdy!

While your scenario may be right on the money, let me point out that some
pilots will claim to be IMC even when there isn't a cloud in the sky.
Their
reasoning is that by doing this, it keep the onus of seperation on the
controller. We both know this isn't quite how it works, but then again, a
chimpanzee flew Mercury 7.


Good point, D. I've actually seen a talking Jackass work an ATC sector down
here, now that you mention it. :-)

Chip, ZTL




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"blanche cohen" wrote in message
...
Um....Bob & Chip...could you explain in more detail the reason
for the "turn into traffic"? I'm having problems visualizing
it. And I have the most horrible feeling that someday I'll run
in the same problem and want to understand it.


To keep it simple, imagine two aircraft converging at 90 degree right
angles. One is heading northbound, one is heading east bound, on collision
courses. Assuming a vertical solution is not a viable option, the fastest
way to achieve separation is to turn one aircraft decisively behind another
aircraft. This kind of turn involves the nose of one aircraft swinging
through the vector (ie- the projected path) of the other aircraft. This
requires a turn towards the other guy. The closer the two aircraft are to
one another when the maneuver is initiated, or the narrower the angle of
convergence, the more of a turn is required. Aircraft types, winds aloft,
other traffic in the scenario etc all play a factor in who gets turned and
how much of a turn is needed. Generally, if all things are considered
equal, one turns the slower aircraft behind the faster aircraft.

This kind of turn can be be counter intuitive to the pilots involved. In
the case of the aircraft heading 090 and the aircraft heading 360, let's
suppose that I issue traffic traffic and then initiate an separation
resolution. To the north bound aircraft, I call traffic at ten o'clock and
ten miles, eastbound co-altitude. I then initiate a vector to put the north
bound airplane behind the east bound airplane. "Turn left heading 310,
vectors behind traffic." To the pilot, I have just issued a turn right into
the traffic I just called. In the controllers mind, I have taken other
factors into play. The east bound aircraft has a tailwind, so the 310
vector will aim the northbound guy into the wind, slowing him down. The
northbound guy was slower anyway. There is more traffic to the south,
precluding a southerly turn to the eastbound aircraft etc etc etc. The
pilot may say "Say again Atlanta? Isn't that where my traffic is?"

The very very basic idea is that assuming I have enough time to aim the nose
of one airplane at the point in space that the other airplane occupies when
I inititate the maneuver, then by the time his nose actually gets there, the
other aircraft has moved on. This assures that neither aircraft will hit
(assuming they don't get together in the turn.) Lots of variables too.

Chip, ZTL





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"Chip Jones" wrote in message
...
[...]
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?

I can't imagine why the Baron didn't turn as you suggested, assuming he
really was IMC. Roy's suggestion that the Baron pilot started the turn
before hearing your suggested vector may be the case, but it seems foolish
of the Baron pilot to make a decision to turn one direction or another
without any input from ATC, if in IMC.

As for whether the other traffic was VFR or not, that's less clear. The
Baron pilot stopped reporting IMC (at least according to your description)
well before the two planes actually converged. It's entirely possible the
Baron did wind up flying out of a cloud, and from that point on was actually
looking for the other traffic. Actually, I suppose if the Baron wound up in
VMC, that might explain the direction he turned and why he was willing to
make a turn without ATC advice.

In any case, keep making those "vectors for traffic" suggestions. Most
pilots, if IMC with no hope of seeing the other traffic, would listen to
you. I know I would.

Pete

Best damn thread in this newsgroup in a while, on topic, interesting
and no one being overly pugnacious. That said...

I think almost everyone can agree on a few basic facts:
-The turn into traffic idea, with appropriate spacing, is a good one
-If a controller suggests an "immediate" change in course... do it
-Traffic avoidence sooner rather than later is best

All that together makes it pretty clear, someone already mentioned
that once the pilot heard "traffic alert" they probably +started their
avoidence right away. without waiting the extra 4 or 5 sec to hear out
the controller... I have no doubt that is what I would do.
So I guess my suggestion to controllers in this situation is to spit
out the vector asap, something like "N123A traffic alert, right turn
to 180 immediately is suggested"... I know it sounds choppy, but I
wouldnt wait a second longer after hearing "traffic alert" to start
what I think is a logical turn. Having "right turn" being the next
words should start the process correctly.
Chip youre a good man, many controllers (well the ones I know here in
the northeast at least) tend to just say "f**king pilot" and move on,
youre actually trying to get a pilots point of view. I hope you got a
better sense of what we're thinking up there, I certainly learned
quite a bit from your posts... im just stoaked about this thread lol.

In article ,
says...
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?

IFR, IMC and no contact, i'd put my trust in you. I'd be a
*bit* concerned about you letting me get to within two miles of
the traffic though.

--
Duncan

In article ,
says...

PS: did you catch up with the "VFR" - traffic.

--
Duncan