Why Does MKE Handle Wittman Traffic?

by ANN Correspondent Dave Slosson

Since February 14, 2008, the airspace over Oshkosh has been controlled by Milwaukee Approach control, instead of Chicago Center. Apparently, Chicago Center wanted to open a new sector for the southbound routes into O'Hare International Airport and needed to divest themselves of this low-level area.

Since Oshkosh is closer to Green Bay than to Milwaukee (35 vs. 68 nautical miles), we asked Wanda Adelman, Oshkosh Tower Manager during AirVenture, why Milwaukee took over the airspace instead of Green Bay. In a nutshell, it's because of equipment capability and existing space.

Milwaukee has a radar display system called STARS, which stands for Standard Terminal Automation Replacement System. Part of that system is installed in control towers that don't have any radar, but whose airport lies within the approach control's boundary. STARS has a capability no other terminal automation system with the National Airspace System (NAS) possesses, called multi-mode. This is the ability to take more than one radar input and display it to the controller simultaneously. The radar controller in this case uses the feeds from Milwaukee, Green Bay, and Madison terminal radars plus Horicon's long-range radar to create a mosaic, or joint picture on his radar scope. Of course, since these displays are all high-resolution, color, solid-state and square, calling it a radar scope like the old days is kind of outdated. It's now termed a controller workstation.

The tower displays are a smaller version with fewer capabilities than the radar displays, mounted either in the main tower like at Milwaukee, or remote towers like Oshkosh. The display in Oshkosh tower is called a TDW, for Tower Display Workstation. This allows the controllers at Oshkosh tower to see the aircraft around them in the air, to a point.

Adelman said the additional information available to the tower controllers has been a real boon. "With a transponder aircraft we can see down to about 200 feet AGL (above ground level), the primaries about 1100 feet and that works really well for us." Before, the arrival aircraft flying by instruments would be verbally coordinated with the Oshkosh tower controllers, and they'd have to find them visually to be able to separate them from other traffic. Now, they're displayed on the flat-panel display and tagged with the N-number or call sign of the aircraft, and the controllers can watch them almost until touchdown. This is a huge safety improvement and will eliminate many delays during instrument weather (less than 3 miles visibility or ceilings less than 1000 feet).

During AirVenture specifically, the controllers talking to the arrivals can use the information to know when to extend the downwind stream to follow the straight-in stream. No more relying on pilot reports of position, which tended to be inaccurate due to pilot workload or forgetting what was requested. There is also silent coordination of the instrument arrivals between controllers since they're tagged on the TDW. This eliminates a minimum of two calls per instrument arrival, one from approach to the tower for the arrival information and one from the tower to the approach controller that the aircraft has landed. The procedures for the instrument departures have not been changed for this year, but more calls can probably be eliminated in the future. Since the TDW also allows most of the surrounding aircraft to be seen, wayward aircraft have a better chance of being spotted and conflicts averted.

Milwaukee received the STARS system due to the volume of aircraft it works. Green Bay's operations are not near the volume of Milwaukee's, and it was a budget decision by the FAA in 2005 that only level 8 facilities and above would receive the STARS. Green Bay is a level 7, all determined by annual traffic count and specific airspace issues, such as controlling a Military Operations Area adjacent or not. Milwaukee also had the space to run another controller workstation, where Green Bay does not.

So Oshkosh got lucky... with a brand new tower and new capabilities that will enhance controller and pilot operations year-round for many years to come.

FMI: www.airventure.org