Lost Arts 4 – Using Radar When You Don’t Have It

It is becoming more and more possible to include Radar “overlay” information into everyday general aviation flying as new technology emerges. But lets not forget that flying and flight training, both VFR and IFR, has been taking place for decades without onboard radar assistance. Are the techniques of avoiding hazardous weather, even without having onboard radar information soon to be included as a Lost Art?

I have taught instrument flight and flown in the clouds for almost 25 years, but only recently have I taught using onboard radar. Most of the light IFR trainers (Cessna 172s, Piper Archer, and the like) that I have used to teach IFR have never had any radar equipment at all. Now it is possible to download weather radar information and have that information displayed on your GPS moving map. The airplane no longer needs to have its own forward-looking radar antenna (although they are still nice to have) in order to “see” what is ahead. But seeing what is ahead is not the same as knowing what to do with that information. How should pilots formulate both a strategic and tactical plan for hazardous weather?

When you are flying VFR or IFR and you have no onboard radar information at all, you can still fly using radar information if you know how to ask for it. Until recently this was the only game small airplanes could play, since onboard radar on small and trainer airplanes was unheard of. Your first evaluation of potentially hazardous weather as shown by precipitation echoes should take place on the ground before the flight. When you fly slow airplanes (100 to 150 knots) it is hard to “outrun” any large weather systems, so your “strategic” planning takes place before departure.

100-150kts: This is the “big picture” plan. In order to fly from Gatlinburg, Tennessee, to Nashville, Tennessee, last summer I first took off to the northeast. Nashville is almost 200 miles directly west of Gatlinburg, but my strategic plan that day was to fly around a large area of thunderstorms so I flew across the western tip of Virginia, got north of the storms. I then flew west along the Tennessee/Kentucky border until turning south toward Nashville after reaching the backside of the storm area. I formulated this plan on the ground while looking at a real-time radar picture in the FBO’s flight planning room.

200 kts: In faster airplanes, you can do some “on the fly” strategic planning, because larger faster airplanes have the speed and range to “head a storm off at the pass.” When you are going 200 knots you can think about changing your plan in flight and making diversions as things develop.

But most big-picture planning in smaller and slower airplanes is done during preflight planning. Once in the air, then you turn to your tactical or “small picture” planning. As I was flying north to get past the storm area, how far north did I know to go before turning west?

I used radar information even though the small airplane I was flying had no onboard radar capability. Here is how…

    1. Talk to the controller you are working with. If you are flying VFR you should get flight following. If you are IFR you will already be communicating with ATC. Ask the controller:Are you painting any precipitation echoes ahead on my current route?

Important: The controller is looking at air traffic radar — not weather radar — and these are very different. The controller will not be able to see very far ahead of you and so can only offer so much help. (Read: A big area of thunderstorms may be sitting just off his/her screen and they may not know anything about it.)

Working the information: If the controller’s screen shows precip echoes it is usually presented in three levels: light, moderate, and heavy. The light echoes usually mean light rain. This rain may or may not be in the clouds – remember radar can’t see clouds, only precipitation that is large enough to reflect the radar beam. If the controller says, “Yes, I show an area of moderate precip ahead in 10 miles,” you ask for a deviation around that weather…

If you can see the weather with your own eyes, then you will be the best judge as to whether or not you need to deviate right or left. The left/right deviation decision also depends on the storm’s speed and direction of movement. In slow airplanes I head for the backside. I figure that I may not be able to beat the storm around the front corner.

If you cannot see the storm because you are flying IFR in the clouds, or VFR in the dark, ask more questions of the controller about the best deviation direction. It is always best to ask these questions early. If you wait until you are already embedded in the storm you will have taken away your ability to plan deviations.

Note: The controller is not actually obligated to answer these questions and any information that they do pass along should be considered suggestions not instructions. When the frequency is highly congested with rapid-fire communications, the controller will not be able to spend much or any time answering your radar questions. And the controllers are not looking at weather radar. In fact the controller’s radar is designed not to show weather, but instead blank out precip echoes so that the airplanes can be seen on the screen better. Mid-range, in-flight, weather planning cannot be done with the controller — you must switch and talk to someone who is looking at real weather radar.

    1. For real weather information, you must talk to FSS or EFAS, but you must get permission to do so first. When talking to ATC you can’t just switch frequencies and disappear. You should say, “Washington Center, this is N1234A, I need to leave the frequency to check some weather.” The controller is projecting your flight and right now may not be a very good time to leave the frequency. There may be traffic ahead, or a forthcoming heading or altitude change in the works that you need to stick around for. Most of the time the controller will grant permission to leave the frequency, but put you on a time limit. They will say, “frequency change approved, report back on in ten minutes.

Note: Before you even ask to leave the frequency, make sure you know what frequency to use to call for weather. Don’t use up half of your ten minutes just finding the frequency. Then make sure you write down the ATC frequency you are leaving or leave it as a “stored” frequency if your radio provides that feature.

  1. Making contact: You can use a direct frequency to call an FSS if you are close enough — use an RCO, or a VOR link if you are farther away. You can also call the Enroute Flight Advisory Service (EFAS) by selecting 122.0 and calling “Flight Watch.” That should work anywhere in the country at 5,000 feet AGL or higher (6 am to 10 pm local). The weather personnel that work FSS and EFAS have weather radar. That means that they can very accurately see where the precipitation is located, but they cannot see where you are. You tell them where you are and where you are going. I always say: “Could you give me a ‘word-picture’ of the precip echoes location and movement?” I get all the information I can, and then when I report back to ATC on the original frequency, I come back with a plan. Once back with ATC, I will tell the controller what deviation I will need, and/or what new routes and altitudes I am requesting.

I have negotiated my way across the country, dodging and weaving safely around bad weather without once seeing the radar screen with my own eyes, but you must know who to ask, how to ask, and give yourself enough time to ask.

THE BOTTOM LINE: I hope I never get so familiar with GPS/radar overlay information that I can’t get around without it. The radar overlay is great — but so far it is slow. You usually do not get instantaneous information and what you do get is just a snapshot of where the precip was located when the overlay was requested. By the time you arrive up where the picture shows an area clear of precip, the precip could have moved into your path. For now (and for some time into the future) the art of using your radio and asking the right questions in a timely manner is your best radar.