This is correct...EFC times are estimates based on a best guess by the controllers. That best guess isn't just a shot in the dark, though. It's based on coordination with the ATC facility downstream who needs the flow held up for a bit, for whatever reason. Most busy ATC facilities have a traffic management position, manned by a person who has access to a lot of information sources and who has the tools to analyze the traffic and provide estimates on EFC times, etc.
One of my favorite web-based aviation authors is Don Brown, an air traffic controller who works the north end of the Atlanta sector. He writes monthly articles for Avweb.com. Coincidentally, his most recent article is all about holds.
After reading the following quote from his article, I got the impression that EFC times *are* more of an educated guess, rather than a well planned coordination of several ATC facilities. Tell me what you think:
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(A quote from Don Brown's Avweb Article, "Holding")
While we're here, let me say a few words about Expect Further Clearance times (EFCs). EFCs are just a guess. They always have been and they always will be. I personally issue EFCs from a pessimistic point of view: I don't ever expect the "best-case" scenario when I'm forced to hold. And it's a rare day I have to reissue a later EFC.
Many of the controllers (perhaps most) I know are more optimistic than I am when it comes to issuing EFCs. That's fine. Different strokes for different folks. It sure is a pain to go back through a stack of 10-12 airplanes and issue every single one of them a new EFC, though.
Still, whether optimistic or pessimistic, the controller is just guessing. Much will depend on the airplanes in front of you. Will they shoot the approach quickly or slowly? Will they land or miss the approach? There are just too many factors at work to be able to give a precise EFC. I know that when pilots are watching the fuel gauges drop, they want to start asking questions. You might pressure a controller into giving you an earlier EFC but all you're getting is still a guess.
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For the entire article, go here:
http://www.avweb.com/news/columns/190503-1.html