Back to Basics: Radar Elevation Bars and Scan Azimuth

This article is aimed mostly to new players. The goal is introducing some fundamental topics in, hopefully, a simple and concise way.
I used the F-14 to visually represent the radar scan volume as I’m more familiar with it.

This is another elementary yet unintuitive topic especially for new players: the meaning of the radar elevation bars and the scan azimuth (sometimes simply called “Width”). Very simply put, both these terms describe the size of the airspace scanned by the radar in the vertical and horizontal plane respectively.

The antenna moves following an “S” like shape: it moves from the left to the right and from the right to the left bar after bar. If only one bar is selected, then the antenna “bounces” between left and right with no vertical movement. The angle between the most left and the most right positions is described the scan azimuth. As you can imagine, the time necessary to complete a full scan is heavily influenced by the number of bars and the scan azimuth.

The number of bars does not affect the total time proportionally as usually a slight overlap is present.

For instance, for the AWG-9:

  • 1 bar = 2.3°;
  • 2 bars = 3.6°;
  • 4 bars = 6.3°;
  • 8 bars = 11.5°.

The scan azimuth settings are, instead:

  • ±10°;
  • ±20°;
  • ±40°;
  • ±65°.

How these number translate into the physical space?

Trigonometry

As discussed a when I made the antenna elevation study (almost a year and half ago already!), trigonometry can be used to approximate how much airspace is covered by different settings of Bars and Azimuth. The result do not represent the exact real value that defines the radar scan volume in real life, nor, probably, in DCS. It is although a pretty good approximation, very useful to understand how the radar works.

I used the values from my model in this video.

“Seeing” the radar: AWG-9

The values reported in the link above can be used to plot a simple and approximated sketch displaying how much airspace is covered by the radar as a function of the distance.
In the next two sketches, red represents the smallest set of values (1 Bar, ±10°), green the second (2 Bars, ±20°), then indigo (4 Bars, ±40°) and the greatest (8 Bars, ±65°).

Radar Elevation Bars
Radar Scan Azimuth

It appears immediate how, the farther from the aircraft, the greater the area covered.

The next two sketches are “slices” of the scanned volume to better show how much area is covered at 25nm and 10nm from the aircraft.
The red square represents 1B, ±10°. The green squares are the two TWS settings, 2B 40° and 4B 20°. The indigo square represents 4B, 80°. The grey square is the widest setting, 8B 130°.

The limitations of the TWS makes it a bad radar mode for building SA and it should be used only when a Phoenix is about to be launched, to IFF a contact or to evaluate a track if necessary.
Note also how the horizontal airspace scanned is much bigger then the vertical airspace. This fact, combined with the issues of limit scenarios (such as high altitude Δ and short range) make operating the radar in the vertical plane much more difficult than on the horizontal.

As expected, at 10nm, the airspace covered by every radar mode is smaller than 25nm, although the magnitude of the decrement is somehow surprising.

The widest mode, 8B ±65° seems the most appropriate when looking for a target we know it is close, but the problem is that the time needed to complete the scan is not a function of the distance (8B ±65­­° always takes around ~14″). The most appropriate radar mode to use depends on the situation, the SA and the experience of the RIO.

I hope the visualizing the volume covered by a radar helps you to better understand the effect of the elevation bars and the scan azimuth. When I moved from RW to a FW, Air-to-air oriented aircraft, understanding the radar volume has been my biggest issue.

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