It Was A Radar Day

Garmin’s new GWX 70 digital weather radar

First we received excellent Nexrad radar mosaic images from XM and Sirius satellites and the way many of us fly changed so much for the better. Now we can receive subscription free Nexrad from a variety of receivers listening in on the ADS-B ground station network. The resolution of the Nexrad picture on ADS-B isn’t quite as good as the pay-for-service satellite displays, but it’s still plenty good.

But, no matter how good those Nexrad mosaic radar images are, there are days when nothing does the job like a radar on your airplane. Last Thursday evening was one of those days for me.

The sun was setting when I took off from Oshkosh headed east for home at the Muskegon County Airport on Lake Michigan’s shore. The rain was moderate over Oshkosh and clusters of cells extended across Lake Michigan all the way home.

The precip was associated with an almost stationary cold front so severe weather wasn’t expected, but there was some lightning about as proof of embedded thunderstorms, and level three and even four radar returns are hardly ever anything but a very rough ride even if the rain isn’t really in a thunderstorm. There were ways around the cells, but the trick was to find them.

I’m lucky enough to have both satellite weather in the panel, and a Garmin GWX 68 digital weather radar in the nose of my Baron. I have to say that the radar spends most of my flight hours idling away in standby mode. Usually when storms are about the satellite Nexrad shows how to make the big course changes that avoids the precip.

But on this day some of the cells were growing with unusual speed. As I flew through light to moderate rain in an area where satellite Nexrad showed no precip, I knew it was time to take a close look at the GWX 68. Sure enough the onboard radar showed returns changing from level one green, to areas of level two yellow, then to level three red in a minute or less. The cells return intensity was changing with every sweep of the radar.

The good news is that the cells were isolated in either an area clear of precip, or embedded in larger areas of light precip, so I could go around them with relatively small heading changes. At one point I popped into the clear and there was just enough light left to see the boiling mass of a building CB exactly where the GWX 68 showed a level two and three cell to be. No pilot would have flown into that cloud if he could see it, but with only satellite Nexrad to go by, I could have nailed the storm in the belly button.

After about 10 years of cockpit satellite weather the NTSB has figured out what most of us have known for years—the Nexrad mosaics sent to the cockpit are many minutes old by the time we see them. The Board has gone into full arm-waving warning mode about the “latency” of these satellite radar displays because during a couple investigations it found that pilots equipped with satellite weather may have nailed a thunderstorm that grew between new radar pictures. In other words, the NTSB has documented what we should all have known—satellite Nexrad is reliable only for wide deviations around storms, not for up close tactical maneuvering.

Onboard weather radar is expensive, and most singles can’t carry a radar, but it is the answer for close in storm avoidance. That’s why Garmin announced the GWX 70, a new solid state weather radar that presents an image more useful, and easier to interpret than the GWX 68.

The GWX 70 eliminates the vacuum tube—called a magnetron in radars—in favor of solid state devices to power the transmitter. That means the GWX 70 broadcasts a coherent signal. When energy is reflected back to the GWX 70 antenna the brains of the system analyze how the frequency of the transmitted signal changed. By looking at frequency changes the GWX 70 can tell the difference between ground returns and precip, and automatically suppress the ground clutter so you see the precip. The system can also measure movement of droplets in the storm and apply Doppler techniques to determine the velocity of the moving drops and translate that as the probability of turbulence.

Other much more expensive radars designed for larger turbine airplanes have had these capabilities for several years, but the GWX 70 is the first “smart” radar aimed at the broader general aviation market. The GWX 70 is available with 10, 12 or 18 inch antennas so it fits in single engine airplanes up to larger business jets.

While there is still no such thing as “all weather” capability, a good radar such as the GWX 68, or even better the new GWX 70, brings you closer to that goal. Weather radar can’t make storms go away, but it can show you where they are in real time so you can go someplace else. So, which do you want, satellite weather or onboard radar? Like most things in life, you want it all.

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9 Responses to It Was A Radar Day

  1. Bill Berson says:

    Sounds like even real time radar may not be enough sometimes. A truly “smart” radar might predict the storm 5 minutes in the future so you can plan ahead.

    • Mac says:

      Hi Bill,
      Of course, no radar can forecast the formation of storms or precip, but Rockwell Collins has a new system that uses a host of factors to analyze radar returns. The system knows the location of the airplane and the date and time of day. Those are crucial factors in knowing if a radar return is from plain old rain or a thunderstorm. And if it is a thunderstorm, how severe is it likely to be. For example, a radar return over Oklahoma in April would usually deserve a wider berth than a similar return over Wisconsin in November. Like other newly designed radars, the Rockwell Collins system uses Doppler techniques to look for movement of droplets in the echo and can also scan the return from top to bottom to provide height information.
      No weather radar can show pilots a positive stop or go sign, but using new techniques and a knowledge of the overall weather situation the new radars make pilots’ job easier, and safer.
      Mac Mc

  2. Harold Bickford says:

    I certainly appreciate the wide range of topics Mac covers. Simultaneously being rated for day/VFR conditions puts on-board wx radar a bit beyond the likely environment.

    The Pietenpol design has worked pretty well over the years with a Mk.1 eyeball and brainiac computer along with a few electronic updates. The one in work in our shop will be so equipped and used for somewhat different flight profiles than Mac might typically be engaged in. In other words aviation is big enough for all flying interests.

  3. Lyman Dellinger says:

    This blog was interesting and I enjoyed reading about the new Radar technology but I am wondering if Mac missed another teaching moment which should always be a part of Sport Aviation.

    Let’s say if he was an instructor or an observer on the ground at Oshkosh and saw a younger man with a wife and 2 children climb into a Baron and knowing they were going to fly the same route over Lake Michigan at that time in those conditions would he offer them any other advice.

    I am not qualified to fly any plane of any sort in IFR conditions over Lake MI but have done so many times as a customer in a back seat of NWA and Delta airplanes. I respect the weather Lake Michigan can toss at people.

    It would be interesting to hear Mac’s thoughts about when it’s appropriate to leave the Baron at Oshkosh with it’s radar and pedal a car around the lower end or to become a customer of Delta. As we grow older and have experienced life, we owe it to the younger generation to share both our positive and negative experiences that we have learned something from.

  4. Hod says:

    Always great reading Mac as he drives EAA into the future with great articles on radar, Barons, Aztec upgrades, IFR, etc. It is useful to see a new facet of aviation and safe IFR operations from a perspective that is primarily the domain of the big boys with their Rockwell Collins and Garmin radar gear. I must say, however, having flown DC-10′s down to Mooney Mites, I’ve learned a great deal about flying from Mac in the last year and how that ties in to the direction that Sport Aviation and EAA is heading.

    I have been truly inspired by Mac to take a look at this: http://www.boeing.com/commercial/aeromagazine/articles/2012_q1/3/
    and see how much of it could best be adapted to a Tailwind. Unfortunately, I’m thinking that the radar system won’t make the cut.

  5. rdt7 says:

    Couldn’t agree more, Mac. I just put in a GWX 68 and have gotten plenty of time using it this summer. It is a vast improvement over my old RDR 160. Do you know if Garmin will have any sort of upgrade program to the GWX 70?

    • Mac says:

      The new GWX 70 is similar in size so it will fit in the same radomes as the 68 but it is entirely different technology so there is no realistic way to upgrade a 68 to a 70. The new radar will display on Garmin flat glass like the 68. Perhaps Garmin will offer some sort of trade in for 68 owners.
      Mac Mc

  6. Robert says:

    How well do you think a Strikefinder or similar device would have worked in this situation, instead of radar?

    • Mac says:

      Any lightning detector helps you identify convective clouds because lightning is a fundamental element of all thunderstorms. I don’t have a lightning detector in my airplane and see lightning only on the satellite weather from XM and Serius but that info is several minutes old by time of transmission and ground stations “see” only a minority of all lightning inside clouds or between clouds. The ground network did not show lightning near my position even though radar returns were growing rapidly to level three. Were those returns thunderstorms or only very heavy rain? No way for me to be sure but I bet they would have been very turbulent. A lightning detector could have confirmed the cells were convective. The way I think of it is that a lightning detector helps keep you out of weather that could break the wings off, but a good radar can help keep you out of weather that can scare you to death even if it doesn’t kill you.
      Mac Mc

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