[ Silence ]
You saw in the video that there were two big conflicts
in Sector 33 when we ran the problem and as Greg mentioned,
air traffic controllers do not have the luxury
of having a simulator to run a problem and see
if there will be conflicts.
As soon as the planes appear on the right side of their screens,
they need to make some predictions
and analyze distances and speeds
to see whether those conflicts are going to occur and to figure
out how to prevent them.
So let's see if we could have predicted those conflicts over,
particularly the one over Modesto.
So let's start by looking at plane speeds
and distances from Modesto.
And we'll begin with Delta 88, that's the green plane here.
And the first question is what's the plane's speed?
Well, Delta 88 is flying at 600 knots.
And how far is Delta 88 from Modesto?
Well, we start our numbering at Modesto and we can count 5, 10,
15, 20, and so on and we see
that Delta is 35 nautical miles from Modesto.
And now let's move on to United down here.
United is also flying at 600 knots
and how far is United from Modesto?
Again, starting our numbering here 5, 10, 15,
United is 35 nautical miles from Modesto.
And finally, how about American?
Well, American is flying at 600 knots
and the first thing you might say is oh,
it's 32 nautical miles from Modesto.
It is sitting on the 32 nautical mile marker.
But be careful, if we count the segments that American flies
to Modesto, we see that from American
to MINAH is 12 nautical miles, from MINAH to Modest--
from MINAH to Coaldale is 10 nautical miles,
and from Coaldale to Modesto is 13 nautical miles.
All together, that's 35 nautical miles.
So now we've seen that all three planes are flying at 600 knots,
all three planes are 35 nautical miles from Modesto.
And that means they will arrive over Modesto at the same time.
And you saw that happen.
So obviously, this is not acceptable.
How do we solve the problem?
Well, what are some ways that we could use
to achieve the 3 nautical mile spacing that we want,
our ideal spacing at Modesto?
One, is we could try a route change.
Another might be to try a speed change.
So let's see plane by plane
for which planes can we change the routes.
Let's start with United.
Can we change United's route?
The only possibility would be to send it
through this thunderstorm.
And we learned in the video that we cannot send a plane
through a thunderstorm.
This route is blocked.
So no, we can't change the route for United.
How about Delta?
Well the only possibility would be to send Delta along one
of these little spurs.
But Sector 33 is an approach sector, we don't want
to send a plane backward and we don't think that a pilot
or a passenger would be very happy about that if we did.
So no we can't change the route for Delta 88.
How about for American?
Well, yes, we can make a change.
We can send American direct from MINAH to Modesto.
And let's see what happens if we do that.
If we do that on the new route,
how far is American from Modesto?
Well this time we can count along this upper route
and we see that American is 32 nautical miles from Modesto.
And in fact it's now 3 miles ahead of Delta 88.
Remember Delta is at 35, American's at 32.
So we have our 3 mile spacing between American and Delta.
And that's just the spacing that we want.
The planes are going at the same speed so they'll keep
that spacing all the way to Modesto.
But we still have a problem between Delta and United.
So let's try using a speed change.
And what we're going to do, we could slow either plane.
But what we will do is to slow United
and we'll slow it to 540 knots.
We'll see that we have a little speed menu here.
And the least speed reduction we can make is 540 knots.
Why do we try that and we're just going to experiment.
We try that because we want to get the last plane there
in the shortest amount of time.
And so we'll just make the smallest speed reduction
possible and see what happens.
So what we're going to do now is see that on a video.
[ Swooshing Sound ]
Now we try to avoid the conflict over Coaldale.
We also try to achieve ideal spacing
and the target time over Modesto.
First, click on reset problem.
To avoid the conflict over Coaldale,
click the American 12 call sign and reroute American directly
from MINAH to Modesto.
This new route is 3 nautical miles shorter
than the original route.
Since the planes are traveling at the same speeds,
American will arrive 3 nautical miles,
ideal spacing, ahead of the others.
To try to obtain ideal spacing between Delta 88 and United 74,
slow United so it will arrive last at Modesto.
Click the United 74 speed and select 540 knots,
the least speed reduction.
Now click Play to run the simulator and see what happens.
We fast forward the problem.
We drag the data tags to make it easier to see the planes.
[ Pause ]
Notice that United 74 arrived late.
So we need to determine when to increase its speed
so it will arrive at Modesto exactly at the target time
with 3 nautical mile spacing.
Well, we did a lot better this time.
We got the planes to Modesto safely
but we didn't quite make the target time
and we didn't make the ideal spacing
between Delta and United.
So, could we do better?
Well, let's first take a look at what the results were.
We see that there are the 3 nautical miles
between American and Delta.
And almost 4 nautical miles between Delta and United.
And instead of the 3:48 target time,
we were 3 minutes and 54 seconds.
So how can we keep United from falling too far behind?
Well, think about what would happen
if you were behind another car and all
of a sudden you were falling very far behind that car
but you wanted to keep your distance.
What would you do?
Well you'd speed up.
And that's what United has to do as well.
But the question is when should we speed up United?
And how fast should we speed up United?
==== Transcribed by Automatic Sync Technologies ====