ATC Procedures - Ongoing General Questions

[Mark Hargrove]

At the really busy airports in the US (in terms of arrivals and departures), at the busiest hour, approximately how many arrival or departure operations per hour will a controller have to work?

[Ryan Geckler]

In terms of strictly arrivals, an ATL final controller will work approx. 40-45 aircraft per runway, per hour. Departures you can get similar numbers.

[Mark Hargrove]

OK, that matches well with a theoretical calculation I did for the Tracon! 2012 forums. As a very back-of-the-envelope estimate, I decided that if the minimum spacing on approach was 3 miles, and the planes were flying at roughly 180 MPH (3 miles/minute), then that was one landing/minute -- so the theoretical max would be 60/hour -- but that no sane person would pack them that tight for that long.

On the other hand, I read somewhere recently that ORD has been known to space them at 2 miles when it's extremely busy. I know for sure that it always impresses the crap out of me when I'm listening to ATC on United on my way into Chicago.

[Keith Smith]

Mark, remember that aircraft may well be doing 180mph when they're 5nm out out at the FAF, but they start slowing to VREF inside of that, leading to all sorts of compression issues. That effectively reduces the arrival rate.

[Mark Hargrove]

Ahhh, gotcha. That totally makes sense!

...and it so totally explains why I'm having trouble with my landings. I'm gonna look into that Vref thing.

[Andrew Doubleday]

Chicago wouldn't be able to space at 2 miles (I've been into the TRACON and ORD many times). That's unsafe and illegal by the book (unless you've got visual separation). Their arrival rate (as with most major airports) is going to be higher when weather is better and visuals can be exercised over instrument approaches. Visual separation means exactly that, plane-to-plane, 3 miles doesn't need to be maintained so long as the approach clearance and instructions to follow/maintain visual with another aircraft is issued _before_ loss of minimum prescribed separation occurs. On a good day, you might get that down to 2 miles inside the FAF, but that's wishful thinking and better hope the front guy can vacate the runway quick enough for the back guy to not receive go around instructions due to same runway separation issues... I think C90 can land somewhere around 110-120 an hour or something on a visual day in west flow to 3 runways (27R/27L/28 arrivals). That's probably close to ATL's numbers. I'd have to check on that number, but that's pretty much a solid arrival flow to all three runways for an hour straight, barring any other issues altogether.

[Mark Hargrove]

New question:

When a handoff from one ATC sector to another occurs (say from center to center, or from center to approach), what is the receiving controller required to say at initial contact from the just-handed-over aircraft?

The dialog from the original controller starts something like:

ATC: "Cessna 123AB, contact SoCal approach on 124.05"
Cessna 123AB : "SoCal approach on 124.05, good day"

Cessna 123AB: "SoCal approach, Cessna 123AB, level one one thousand"
ATC: ???

I don't recall ever hearing "Cessna 123AB, SoCal approach, radar contact"; rather, I seem to recall it's something like "Cessna 123AB, SoCal approach, roger"

Which is correct phraseology?

[Keith Smith]

"radar contact" is used exactly once to inform the pilot that radar services are being provided.

Listen to the PE ATC recordings, you'll quickly hear that when a pilot checks in with the NEXT radar controller, the controller basically gives the local altimeter setting if the aircraft is below the flight levels. Depending on the phase of flight, the controller might tell the aircraft which approach to expect and then start vectoring/descending as appropriate.

[Mark Hargrove]

Thanks Keith.

I thought of listening to the recordings just after I posted the question. After listening to a bunch of different departure/center/approach recordings (most of which were initial contacts at the places I was sampling), I did finally hear an example of what you said (and what I thought I recalled).

-M.