In the spring of 2003 Concord ATCT received a tower radar display. Until now we've operated without radar. Concord ATCT is what's referred to as a "VFR tower" which means we do not provide IFR separation. What we do provide is runway separation. We also provide additional services such as traffic advisories. Our primary tool for this is our eyes. We have a great view of the runways and on good days we can see pretty far. But even on clear days it can be difficult to see a white Cherokee against a bright sky only two miles away. If we had better eyes, we could see farther.

Well now we do. The kind of radar we have at Concord is considered to be just that: "an extension of our eyes". That's another way of saying that the set of rules we apply to separation of aircraft does not change with the addition of radar. So what does this mean to you as a pilot?

First of all it means that there will be no significant procedural changes with the addition of radar. Concord airspace is still a Class D surface area. And it's still a "see and be seen environment". The same rules apply as before. You will not be required to contact Clearance Delivery prior to taxi if you're VFR. Nor will you be required to have a discrete transponder code for VFR flight. Departure and arrival procedures will be exactly the same as they have been: get the ATIS, then call ground or the tower with your request. IFR procedures will be unchanged, too, with the same "one in, one out" policy.

When most pilots hear the word "radar" they automatically think "vectors". You will not be getting vectors from Concord tower. The equipment we have is not certified for that kind of service. We cannot give you vectors for an approach, vectors around traffic, vectors to join an airway or any other kind of vectors. We can provide suggested headings. But these are advisory only - and we have to call them "suggested headings". When we issue traffic it won't be with clock positions. We can say "traffic ahead to your right", but we can't say "traffic two o'clock, one mile". If the traffic has mode C, we can tell you what that is indicating. (Remember, if we say that traffic is "indicating one thousand five hundred", it means that the mode C is unverified.)

Why can't we use our radar the way an approach control would use their radar? The short answer is "it's not certified". A better answer is that it is a feed off of center radar (ARSR). The refresh rate is extremely slow: only once every twelve seconds. That's fine when you're working high altitude with areas spanning hundreds of miles and five mile separation standards. But by the time our radar sees you on base leg, you're already on short final. Things happen much too quickly in a terminal environment to trust a twelve second sweep.

Another shortcoming of this radar system is its spotty low altitude coverage. Again, center traffic is usually at high altitudes. Our traffic is below 2500 feet. The radar site itself is actually in Marin County. The hills between Concord and Marin create "shadow" areas of poor coverage. Consequently targets occasionally disappear only to reappear again in a different place.

So what good is this "radar"? Actually it's a lot of good and will enable us to provide better overall service. We'll be able to "see" farther than we can using only our eyes. With the mix of traffic we have here at Concord, we'll be better able to sequence high performance aircraft further out. We'll be able to confirm that an aircraft calling inbound is really where they say they are which will enable us to give the most appropriate entry instruction. We'll be better able to sequence traffic around other aircraft inbound on an instrument approach procedure. We'll also be able to provide better assistance to disoriented aircraft.

Until now if two aircraft called inbound from the same general area, we were required to exchange traffic information. Having a tower display helps us to determine if those two aircraft are really traffic for each other. If they're not, then we don't have to exchange traffic. By not having quite so many traffic calls to make, we then are able to free up the tower frequency so that other pilots can use it. Frequency congestion at Concord has long been one of our biggest problems and an irritant to pilots and controllers alike. Anything to lessen the frequency congestion will be an improvement.