Airborne Weather Radar — Page 220, Lesson 206

I want to walk you through the operational side of the Airborne Weather Radar now — how you actually use it to avoid thunderstorms, and the controls you'll find on the unit. This is where the theory turns into real flying technique, so let's take it step by step. Weather Operation — Avoiding Thunderstorms First, the core strategy. You select the maximum range on the radar so you detect weather formations in good time — that's your early warning. Then you adjust the TILT control to remove ground returns. Remember, the radar beam is tilted up and down; if it's too low, you'll paint the ground instead of the weather, which clutters your display and hides the real picture. If the storm system is extensive, you make an early track adjustment, in consultation with ATC, to avoid it. That's the key phrase — early. You don't want to be threading the needle at the last minute. If avoidance isn't possible, then as the clouds get nearer, you select the lower ranges and the CONT mode — that's the contour mode, which highlights the intense precipitation — and you determine the best track to avoid potential turbulence. Here's the critical judgment point: ensure that short-term alterations of heading steer the aircraft away from the worst areas, and not deeper into them. That sounds obvious, but it's a real trap — you can make a small turn that looks good on the short range but actually bends you into the heart of the storm. To achieve this, you need constant switching between short, medium, and longer ranges, so you maintain a complete picture of the storm system. You're never locked on one range; you're always cross-checking. Shadow Area Now, a danger you must understand. There's the risk of not being able to map the area behind heavy rain, because no radar waves will penetrate it. The radar beam is attenuated — absorbed and scattered — by that intense precipitation, so the area behind it shows nothing. That's the shadow area, and it may contain severe weather. So an empty patch on your screen is not necessarily clear air — it could be hiding a thunderstorm behind a rain cell. Never assume a blank area is safe. Height of Storm Cloud You can ascertain the height of a storm cloud by adjusting the tilt until the radar returns from it just disappear. As you tilt the beam up, the returns fade; the point where they vanish marks the top of the cloud. Then you can calculate the height of the top using the 1 in 60 rule — the rule that a one-degree angle subtends roughly one unit of height at sixty units of distance. So if you know your slant range and the tilt angle, you can work out the cloud-top height. And a practical warning: a thunderstorm may not be detected if the tilt setting is set at too high an angle. If you've tilted up to look for cloud tops, you can literally miss a storm that's right ahead of you at lower altitude. So you manage tilt carefully — high enough to avoid ground returns, low enough to see the weather. Height Ring Now, on the older AWR systems — the ones where the conical beam is produced by a dish antenna — there's always some vertical overspill of energy. That energy spills above and below the main beam, gets reflected back to the aircraft, and appears on the display as a height ring. That ring roughly indicates the aircraft's height — it's a rough altitude reference. It also serves a second purpose: it indicates that the equipment is serviceable when there is no weather ahead. If you see that ring, you know the radar is transmitting and receiving properly, even in clear air. Colour AWR Controls Let's move to the colour systems. The controls for a colour AWR are similar to the monochrome unit in terms of range, tilt, and gain — same fundamentals — but they may have additional features. Let me name them precisely: - Wx — that's Weather mode. - Wx + T — Weather plus Turbulence. - Wx(var) — Weather with variable gain control. Other sets may have a WxA control, which stands for Weather Alert. That gives you a flashing display of the areas associated with turbulence — it draws your eye to the dangerous zones. There may also be a Contour Intensity control, which lets you adjust the display for optimum presentation — you can tune how the contours are shown so the picture is as clear as possible. Now, the latest AWR controls are activated by push ON/OFF switches located around the colour screen. And one of those is the Test function. Test displays the colour pattern for a pre-flight serviceability check — you run it before departure to confirm the radar is working correctly. So, to tie it together: your operational sequence is maximum range and tilt management for early detection, early track adjustment with ATC, then progressive range reduction with contour mode as you close in, constant range switching to keep the full picture, and an awareness of shadow areas and cloud-top height. And on the panel, you've got Wx, Wx + T, Wx(var), WxA, Contour Intensity, and Test — each with a specific job. That figure shows a basic control unit for a monochrome AWR with range scales of 20, 50, and — as you can see — the range, tilt, and gain controls we've been discussing.