John Kulp wrote:

Ah, no. GPS was not designed for that nor can it provide that. Most in
trail separation today is based on wake turbulence. Even if you got rid
of wake turbulence you still can't get less than 2.5-3 miles for jets
because that's how long it takes to land, slow down and exit the runway.
If it's dry. And that spacing doesn't allow departures to get out
between the arrivals. So you go to five miles and if everything works
out perfect that's barely enough room to get the jet departures out.
The plain simple fact of the matter is the limiting factor is lack of
runways. No amount of technology can force more airplanes onto the
runways we have now.


Funny none of the airlines I know of are saying this. They are all
advocating just this upgrade and the FAA is going to have it build.
So just what do you know that those running the business don't?

GPS was designed and built by the military. Imagine that, the airlines
not wanting to change anything but have others change to meet their
outmoded business plan. You can't change basic physics. GPS can
generate some minor efficiencies in getting aircraft to the start of the
arrival which is 150 nm from the airport. Then everybody gets lined up
and fed to the airport. GPS is of little value from that point on in
reducing spacing. How are you going to overcome the basic fact that
2.5-3 miles is the minimum useable spacing, assuming no departures?
Many studies have been done that the optimal runway occupancy time is
approx 45 seconds for a landing aircraft. More typical is 1 minute, in
good weather. That's approx 2.5-3 miles separation. You want more
operations? Lay more concrete.