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Turbulence can be encountered in the clear air around a cell.
focus remains the separation of IFR traffic. Controllers are available to provide information, but they do not always offer it unsolicited. If you fly in less developed countries, be aware that controllers may not have access to weather, and that there may be large gaps in ground radar coverage when using data-link weather. Do not assume a lack of displayed weather means that the area is free of convective weather.
Be proactive in asking controllers for information. Un- derstand the services that are available in the airspace that you are flying in. If you are unsure whether controllers have weather depiction capabilities along your route, ask them. It is easy to fly yourself into a corner when deviating around closer weather while being unaware of more distant cells that are behind. ATC and data-link services fill the hole nicely, providing hundreds of miles worth of radar information to help generate to plan of attack.
While ground radar is a great supplementary tool, in practice, it possesses some shortcomings as well. You will occasionally find radar echoes observed inflight differ substantially from those produced from the ground. There are many assumptions that radar systems utilize to depict weather, and this can create conflicting information. Prop- erly functioning airborne radar is the most reliable resource for making decisions en route. Not only will it keep you safe but it can (at times) shave off hundreds of miles worth of needless deviations.
Weather radar is a precipitation detector, plain and simple. It can detect other things as well –namely the ground – but its design and purpose is to display the precipitation that normally accompanies convective activity. It is important to recognize that the presence of precipitation in and of itself does not mean that the area cannot safely be navigated. Precipitation echoes can also be associated with broad, non- convective rain showers as well. You want to err on the side of safety, but you do not want to divert due to a little rain.
Convective buildups come in many different shapes (there is an entire catalog of radar shapes that meteorologists use to identify extreme weather), but most hazardous weather shares this in common: well defined red or magenta areas encircled by a relatively narrow band of yellow. Extremely sharp gradients in intensity represent violent storms that should be given plenty of room. Magenta returns also in- dicate areas to avoid.
Nonhazardous rain showers tend to appear splotchy, with gradual and uneven gradients from red, to yellow, to green. If other sources indicate that these areas are benign (such as
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pilot reports, lightning strike indicators, or tower reported surface winds), they can generally be transited without fuss. The decision to proceed, delay or divert should be made as early as possible based on the best information avail- able. As you prepare for an approach at an airport with questionable weather, ask ATC what they are depicting and solicit suggestions for approaches that will keep you clear of significant returns. Outside of 100 nm, onboard radar is of limited use (it does a good job displaying well-defined lines of weather, but small isolated cells – even when there are dozens of them in a concentrated area – are oftentimes not displayed at longer ranges). Controllers in these cases
can be a reliable source of information, if only you ask. The approach phase of flight is high workload, and be- coming fixated on the radar can greatly erode situational awareness to other required flying duties (always remember: aviate, navigate and communicate). Assess the information available, commit to a course of action and adjust only if new information arises which is relevant. Second-guessing is a worthless distraction. Focus your attention on flying the airplane instead. Thunderstorm encounters are a much less common cause of accidents than Loss of Control In-
flight (LOC-I).
You should remember throughout the process that divert-
ing to an alternate represents the successful completion of a flight. The only measure that matters in aviation is a safe landing for every takeoff. To the degree that pressure exists to land at your destination, you must purposefully ignore that impulse and focus on making a smart decision. Do not roll the dice with your life or the lives of your passengers. If you have any serious question about the intensity of the weather, either divert or (if you have enough fuel) hold until it clears.
Enjoy The View
There is one thing that is better than radar: When in visual conditions, the best way to avoid hazardous thunderstorms is to use your eyes. There is no device on our increasingly sophisticated aircraft that beats biology.
Radar is supplementary in the case of visual flight, but still important. It is quite difficult to determine the dis- tance to cells by sight – a function that radar excels. It is also under visual conditions that we become increasingly comfortable with interpreting radar images. Since we can actually see the cells, it provides direct feedback in develop- ing a mental picture from the radar display for those times when visibility is restricted.
For all the platitudes of weather radar, there is nothing safer and more pleasing than remaining in visual conditions to enjoy – from a safe distance – that beautiful, powerful and awe-inspiring cumulonimbus.
Stan Dunn is an airline captain and check airman. He has 7,000 hours in turbine powered aircraft, with type ratings in the BE-1900, EMB-120, EMB-145, ERJ-170, and ERJ-190. Stan has been a professional pilot for 14 years, and has been flying for two decades. You can contact Stan at Stan@flyingfor- money.com.