Airborne Weather Radar — Page 220, Lesson 208

Right, let's pick this up with the weather radar controls. We've covered the basic range and gain settings, and now we're looking at the more advanced functions on the control unit. We have three specific features to examine here: HOLD, TGT ALERT, and FAULT. First, the HOLD facility. This is a very practical tool for assessing storm movement. The idea is simple: it freezes the display so you can compare where a storm was against where it is now. Let's say you've located a storm at, for example, 100 NM. You select HOLD, and you must maintain a constant heading. When HOLD is active, the words "HOLD" and "WX" will appear alternately on the screen. You leave it like that for two or three minutes. Then, you deselect the HOLD facility. This brings back the current, live display. Now, you'll see the storm's position has moved from its held position to its actual position. That movement, relative to your aircraft, tells you the storm's direction and speed of travel. It's a direct comparison of the frozen picture versus the live picture. Next, we have TGT Alert. This is a warning system that works in conjunction with the WEA facility, which is the weather detection mode. Its job is to alert you to a storm return of contour strength. Now, what does that mean? A "contour" return is a strong, intense echo that the radar would normally display as a solid, filled-in area. So TGT Alert is specifically looking for those intense returns. When you select TGT ALERT and there are no contouring clouds present, the screen shows a yellow "T" inside a red square, located at the top right of the screen. That's your standby indication. However, if a contouring cloud is detected within a specific range and bearing — that is, within 60 to 160 NM and within plus or minus 15 degrees of your heading — then the symbol changes. Instead of the static "T", you get the yellow symbol "TGT" in a red square, and it flashes on and off once a second. That flashing is your alert that a significant storm is ahead. Finally, we have the FAULT indication. This is your system health monitor. It's controlled by a fault monitoring circuit. If there is a power failure or a transmitter failure, the word "FAULT" will flash on the screen. This is a critical check — if you see FAULT, you know the radar is not transmitting and you cannot rely on it for weather avoidance. So, to summarise the three: HOLD freezes the picture to track storm movement, TGT ALERT gives you a flashing warning of intense storms within a specific window ahead, and FAULT tells you the system has failed. These are all essential for using the radar as a safe, effective tool in flight.