Basic Math Behind Radar Tilt

There's no doubt about it: as we get into summertime, we're transitioning into the fun game of dodging storm cells. 

The air is hotter and more unstable and quickly builds into convective-type clouds that keep rising into the troposphere, next thing you know you have pop-up thunderstorms everywhere. The job gets especially fun as they grow into squall line thunderstorms. The best way to stay safe in these situations is to plan ahead, always have a backup plan, let ATC know what you need, then cooperate with them, and know how to use your radar.

Clouds in the Sky

Each radar is slightly different from the other but for the most part, they work very similarly. The first step to knowing how to tilt your radar is knowing how long your antenna is. The length corresponds to the beam it puts out. For example, a 10-inch antenna puts out a 10-inch beam, 12 inches has 7.9 degrees, 18 inches has 5.6 degrees and lastly, 24 inches has 4.2. So as the length increases, the beam degrees decrease.

If you happen to know the width of your beam in degrees then you can figure out your tilt with a little math. This photo and mathematical formula from Code 7700 explains it simply using the G450 as an example, where they have the 24 inch 4.2 degree beam:

Beam Width Gulfstream G450

So at 45,000 ft, it would take 100nm to paint the edge of the ground clutter, and tilting the beam to 2.1 degrees would point it at level flight. 

While it can sound a little confusing at first, using this formula and adjusting the tilt at the same time will help you adjust to being able to tell when you have the radar set how you want and when it needs to be readjusted. A good practice is to always use your radar while you're trying to learn it, even to see terrain rather than the weather. Most would recommend whether you're in the Texas flatlands or near high terrain in California that it's good to have your terrain feature on. 

Weather Radar on Map

Something else I like to do to double-check I have the tilt on an accurate setting is to see if I have service/wifi onboard like this G450, open up that Foreflight radar (or your most trusted radar app, also highly recommend MyRadar). After all, two is better than one!

The last tip, but most definitely not least to trust your onboard radar, is if you're VMC, simply look outside. Night or daytime, you can see lightning and guestimate where that cell is in relation to you. If you're not sure how close it is, take a 10-degree deviation off course to feel safe. ATC 99.999999% always approves deviations for the weather. They want you to land safely just as much as you do. 

Hope everyone is ready for the summer flying season to take place! Remember to be knowledgeable, be safe, and download the BuyPlane app. Safe flying everyone.