WAM
WIDE AREA MULTILATERATION COMES TO YLW
BY ROD SHUTTLEWORTH F lying in and out of
mountainous terrain is never easy, but at YLW it just became a lot safer thanks to the 2010 Vancouver winter Olympics.
Sam Samaddar, Airport Director, explains: “We heard about technology which was being installed in the Sea- to-Sky corridor to help control aircraft movements to and from Whistler during the Olympics, and wrote to NAV CANADA asking if it could be re-deployed to YLW when the games were over and it was no longer needed.” NAV CANADA, which provides air traffic control, flight information, weather briefings, aeronautical information services, airport advisory services and electronic aids to navigation from coast to coast, agreed, and by summer 2012 the new Wide Area
Multilateration system (“WAM”) was in place and ready to go.
Prior to the installation of this system, air traffic controllers relied on a radar installation near Salmon Arm to locate and track aircraft in YLW’s airspace. The problem with radar is that it can’t see through solid objects like hills, so in YLW’s case the radar could only locate aircraft down to approximately 3000 feet above sea level. Once aircraft dropped below that altitude on approach, or before they reached it on departure, controllers relied on radio contact, with pilots reporting their positions at regular intervals. This required controllers to maintain a mental map of aircraft location, and to leave wide gaps between aircraft as a safety margin.
The new WAM system consists of 9 small receiving units (RU) placed at strategic locations around the valley. A master RU sends a signal to the transponders that all aircraft, including light aircraft, are mandated to carry in the Kelowna Control Zone. The transponders reply with a specifically coded “Squawk”. The differences in the time it takes this signal to reach each RU enables the system to triangulate the exact
location of each aircraft. Signals from the RUs are sent back to a computer in the YLW control tower which calculates the aircrafts’ positions and then sends that information to NAV CANADA’s area control centre in Surrey, where it is seamlessly integrated into the existing radar data before being sent back to YLW (and to any other authorized users of the information) as an instantaneous image on the existing radar screens in the control tower. As Paul England, NAV CANADA’s Site Manager at YLW puts it: “WAM filled in the missing spaces.”
As a result, air traffic controllers can now see the exact location of all transponder-equipped aircraft from the moment they enter the airspace right down onto the ground. This is particularly valuable at night after hours when YLW’s air traffic is monitored by Penticton Flight Service Station, but has also created significant improvements in both safety and efficiency for all YLW’s air traffic. With accurate information on aircrafts’ location, controllers no longer
4 | YLW CONNECTION
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