Thanks for the great reply, right on target. I would like to inquire a bit
further.

"TJ Girl" wrote in message
om...
Hopefully this will clear a bit up...
The Center's computer contains a subset of fixes that includes all
within that center's boundaries, a lot of the adjacent center's fixes,
and the major fixes nationally.

Can you shed any light on the rules for including fixes from adjacent
centers? Is it everything within 200 nm of the center boundary? Or just
airway VORs?

However, any center's computer can
understand a latitude/longitude location.
In order to "process" a flight plan, the center must understand the
route up until the first fix outside the center. This is why a lot of
controllers will put in the flight plan "route..lat/long..fix at that
lat/long" - here the host (Center) computer only processes up to the
first lat/long and doesn't care what comes after it, so the unknown
fix can be included without a problem. Many controllers also just put
a nearby major airport as the destination and put the real destination
in the remarks, then a controller in the destination center, or maybe
one adjacent to it, can put in the correct destination.
As far as processing, this means that the computer "knows" where you
are going. The controller can display route lines. Your target will
flat track instead of free track - which means the computer predicts
your future position based on flight plan data, instead of just your
history. You can auto-hand to the next sector - which means the
computer will start the handoff at a specified distance from the
sector boundary if the controller has not already initiated it. It
means things like conflict alert will be more accurate, because the
computer knows where you are expected to go and is not just guessing
based on where you have been. Basically, it just comes down to
meaning the computer (and therefore the controller) know what you are
going to do.


What does the computer do if it cannot process fixes to determine the route?


Do all the computers store all the airports?

They don't store all, but will store all the major ones, so it really
just depends where your destination is.


Is there a simple rule for what constitutes a major airport for this
purpose?


Do they all store
some subset of the total database, and is the way the local database is
constructed uniform across facilities, or is it variable because of
equipment, or local policy, or what?

They store a subset, as mentioned above. The theory is space
limitation. The new URET system stores the entire Jeppesen database,
so you should start to see this problem go away (and new ones arise).


What is the extent of deployment and use of URET?