Neck of the Funnel

Isabel Goyer

Friday, July 29, 2011 at 01:53 AM ET

Verified

Key Takeaways:

Oshkosh arrival procedures are complex due to the high density of converging aircraft (a "funnel" effect) and less ATC control over incoming pilots, making collision risk higher.
Departure procedures are simpler because aircraft naturally disperse quickly (a "reverse funnel"), and ATC has more control over takeoff timing to ensure separation.
The primary concern during departure is avoiding arriving aircraft, addressed by NOTAM guidance to climb above their altitude before turning out of the area.

See a mistake? Contact us.

Have you ever wondered why the departure procedures from Oshkosh and its surrounding airports are so brief compared to the complex arrival procedures that govern airplanes heading into the show. It’s an easy explanation.

Think of airplanes as being water flowing to Oshkosh and of Oshkosh as being a big puddle of airplanes located directly beneath that funnel. Air traffic control is concerned primarily with airplanes not running into each other. At Oshkosh, they’re not even particularly concerned about them not getting too close–the air show has reduced separation standards or else all those airplanes would never be able to make it in.

Mathematically, the worrisome parts of the operation, when airplanes might collide, is when there are a lot of them in close proximity to each other. That is, when they are flowing down the neck of the funnel to the runways.

On departure, ATC has a lot more control over things, because they control when the airplanes take off–there’s a lot less control when those airplanes are coming in to land, as their pilots can do any number of unexpected and potentially frightening things.

So when airplanes are leaving the airport, they are under ATC control for long enough to allow them to disperse naturally into the airspace. The biggest concern, really, is that they don’t collide with arriving airplanes. That’s why the notam directs airplanes to climb above the altitude of arriving traffic before turning toward the arrival routes.

Here it’s a reverse funnel. After just a few minutes, your chances of encountering and colliding with another airplane are very remote.

What this means is that you should pay attention to the notam’s guidance to climb and to just get out of Dodge. They really do care about you hitting another airplane, but they know that the chances of that happening when you’re heading out the other end of the funnel are extremely slim.

By all means look out for airplanes when it’s time for you to head home. But while you’re at it, do take a deep breath and reflect upon what a great time you had at the show.