Riddle me this, pilots

"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
...
This kind of turn can be be counter intuitive to the pilots involved.

Yup. It was to me until I gave it more thought.

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."

The "vectors behind traffic" phrase sounds very useful. It concisely
explains to the pilot, in real time, why the counterintuitive instruction
actually makes sense.

Thanks for posting this. If I'm ever in such a situation, having thought
about it beforehand might help me avoid wasting a second or two trying to
figure it out.

--Gary

On Tue, 19 Aug 2003 11:44:03 GMT, "Gary L. Drescher"
wrote:

"Chip Jones" wrote in message
...
This kind of turn can be be counter intuitive to the pilots involved.

Yup. It was to me until I gave it more thought.


Actually, to me it seems quite logical and would have been my initial
reflect to turn TOWARDS the conflicting traffic, since the whole
purpose of the exercise would be to change the constant bearing of
closure.. turning away from it will only slow the rate of bearing, not
necessary change the angle (as viewed from overhead both, not as in
"clock" positions from the pilot's perspective).. turning towards it
will increase the rate briefly until the vector angle is depassed and
then it will widen again. Of course if the other traffic does the
same thing, then you're going from a constant relative 90 degree
closing bearing to a constant relative head-on closing bearing which
will also be a bad thing... of course in this particular case the
other [unidentified] aircraft was seen to maintain his course.

Leland

"Chip Jones" wrote in message
...
This kind of turn can be be counter intuitive to the pilots involved.

Yet in high speed driving school (i.e., Bondurant) they teach you to swerve
BEHIND a car coming across your path. Most drivers will just slam on the
brakes. In fact, in most every situation the vast majority of drivers will
just slam on the brakes rather than maneuver out of the way. It's the
hardest habit the driving instructors have to break (pardon the pun).