Waypoints

Editor in chief Thomas B. Haines has been flying various Stormscope-equipped airplanes for 15 years.

Apparently, I've purchased a thunderstorm repellent and suppression system. If so, it was an excellent investment.

I thought I was buying a Goodrich WX-500 Stormscope to tell me where the storms lurked. However, in two trips into the thunderstorm cauldrons of Florida and Texas during April, when boomer season ought to be ramping up to full tilt, I've seen only an errant strike or two — none of them showing any real convective action. The cynic in me believes that had I made the same trip sans such equipment I would have been dodging Level 4 cumulonimbus left and right.

Thunderstorm detection gear, generically called spheric devices by those who build them — spheric is a shortened form of "atmospheric" — has been at the top of my must-have list since before I bought the Bonanza two years ago. Even when I had a Cessna Skyhawk, which I used for shorter trips, I yearned for such a system. When you fly in the Northeast and Mid-Atlantic, almost any spring or summer day brings with it the admonishment from flight service of a "chance of thunderstorms." One Skyhawk flight in particular drove home the point for my wife, who is an excellent passenger and navigator. What should have been a simple 1.5-hour flight home turned into a couple of hours of circumnavigation and uncertainty as we maneuvered between unseen monsters embedded in cumulus clouds all around us. "Why don't you get a Stormscope?" queried the keeper of the checkbook. Permission is good. But before I could decide on which system to get, I decided that what I also needed was an airplane that made more sense for my typical long-distance flights.

Although there have been many Bonanza flights over the past two years where a spheric device would have been helpful, I've held off buying one until I could decide how I wanted to display the information, not to mention the checkbook issue.

It used to be easier to decide what to buy. You had one choice: Stormscope. Inventor Paul Ryan patented the device in the 1970s and eventually sold it to the 3M Corporation while he went on to develop the Ryan TCAD traffic alert device, which has now grown into a full product line of its own. 3M further enhanced the Stormscope product line with what it called "Series II" technology. 3M sold the product line to BFGoodrich, now known simply as Goodrich. Goodrich continued the development and currently offers a complete line of Stormscope products.

Competition entered the scene in the 1980s when Insight Instrument Corporation introduced the Strike Finder. The Strike Finder remains relatively unchanged, although Insight now offers a brighter display and a self-contained system for adjusting the display so that it shows the strikes relative to your actual heading — a real boon to those without a remote electric compass system.

For light general aviation airplanes, those are your onboard choices at the moment for display of lightning data.

I'm often asked by AOPA members considering such equipment whether I'd rather have lightning information or weather radar. Both, is the obvious answer. The devices are completely different technologically, but the information they provide can complement one another.

Spheric devices are passive. Basically, they listen for and then plot on a display the electrical discharges associated with lightning. Since lightning is always a byproduct of thunderstorms, if you stay away from lightning, you'll avoid the storms. Radar is active. It throws out an energy beam and measures how much of it is reflected back by precipitation — or the ground, if the antenna is tilted downward. Radar accurately depicts varying levels of precipitation intensity. Avoid the intense areas of precip and you'll avoid the thunderstorms.

Unfortunately, radar is seldom an option on light general aviation airplanes for a variety of reasons. For one, it's expensive. Expect to pay a minimum of $15,000 for the most basic system. But with most airplanes, cash flow is the least of the problems. Real estate is the bigger issue. In your average GA airplane, there isn't any place to put a decent size radar antenna. A few airplanes, such as Bonanzas and Cessna 210s, have been certified with radar pods beneath the wings or ahead of the leading edge, but the tiny antennas inside can't receive enough of the returning data to give as clear a storm picture as the big, powerful radars on business jets and airliners.

The light radars can be effective in avoiding areas of precipitation altogether. But if you find yourself in rain trying to avoid the heavy rain associated with thunderstorms, the low-power systems will usually begin to attenuate to the point that they become worthless. In other words, the light to moderate rain just ahead of the airplane relects all of the radar energy, painting a continuous green swath on the radar display. Meanwhile, the heavy rain farther out and possibly in your future is masked. Systems with greater power and larger antennas can punch through the local showers and give you the bigger picture. But even the most powerful airborne weather radars are subject to attenuation in extreme situations.

And there's the matter of interpretation. Learning to understand what the radar display is telling you is truly an art form. What are the telltale signs of attenuation? Why is a hook-shaped return just about the worst sight you can see on an already bad day? If you don't know the answers, you had better leave the radar at home or at least attend a course offered by radar experts Dave Gwinn or Archie Trammell, among others.

Spheric devices demand their own level of interpretation. All of them suffer from a phenomenon known as radial spread. In sort of a reverse of attenuation, radial spread displays strong storms beyond the device's normal 200-nm range. The classic sign of radial spread is a wedge of dots streaming from the edge of the display to where your aircraft is depicted. To the uninitiated, a storm 300 or 400 miles away can seem to be right on top of you. Newer versions of spheric devices do a better job of suppressing radial spread, but it's still an issue.

Until recently, installing a Stormscope or Strike Finder meant a new display in the panel and, depending on the model of Stormscope, possibly a remote processor as well. Within the last couple of years, though, the Stormscope WX-500 model has outstripped the sales of all others. It is basically a remote processor connected to your favorite moving map or multifunction display already installed in the panel. With the WX-500 you needn't give up precious panel space, and the lightning data is displayed relative to your route of flight. Bootstrapped to your remote electric compass system, the device keeps the dots oriented properly relative to your changing heading.

The downside is that with most lighter GA airplanes you normally navigate with the moving map set at 50 or 100 nm while the dedicated Stormscope display is set at about 200 nm to provide lots of advance warning. Most of the moving maps get around this by providing a dedicated Stormscope page on their displays that can be set to your favorite distance, and they provide a strike counter on the main moving map page to alert you to possible distant storms.

For me, the debate has been whether I should nab the one remaining hole in my panel for a dedicated Stormscope or whether I should get a WX-500 and display the weather information on the Garmin GNS 530 GPS/moving map/VHF navcom that I had installed last fall. Ultimately, I decided that the benefit of having the storm information displayed relative to the moving map information was very valuable, so the choice was the WX-500.

Of course, that created yet another dilemma: What to do with that one remaining hole. It just wouldn't do to have it blank. In fact, located next to the turn coordinator, the hole is the perfect place for an electric standby attitude indicator to back up my air-driven primary AI — another safety device from my list. Whew, problem solved.

So in March, I delivered the airplane to Gulf Coast Avionics in Lakeland, Florida, for the big Stormscope and standby-AI upgrade. Two weeks later I flew the 725-nm trip home through the normally convective Southeast without a storm there or anywhere else. Within the next couple of weeks I made a few short trips and a journey to Dallas — 1,000 nm each way — all in electrical silence. I couldn't find a storm to save me.

Best insurance policy I've ever bought.

E-mail the author at [email protected].