There’s a reason why Garmin and others dedicate entire pilot training courses to ship-based weather radar operation. I completed a couple of these courses and learned that if you’re new to using radar to strategically work your way around weather, you’ll want a solid understanding of control logic and reading the display graphics before making a run at serious weather.
While not a substitution for weather radar training, Garmin has automated the chore of tactically using its GWX 8000 StormOptix radar and GTN 750Xi/725Xi aftermarket navigator interface, borrowing a feature set and logic used in its OEM integrated flight decks. This includes automatic control over the radar’s tilt and gain commands.
For helpful tips on installation, we’ll also talk about caring for aging radomes.
Auto mode
That’s the key to simplified operation because it might eliminate operator error (and reduce workload) from the critical task of manually adjusting the radar’s scanning. The Auto Mode (a single soft key on the GTN 750Xi (and TXi flight display, where the feature is also available) really does take the science out of working the radar because you don’t have to manually tweak the radar’s gain and tilt control.
Worth mentioning is that the GWX 8000 StormOptix radar has been around for a while. It’s Garmin’s flagship weather radar that caters to the turbine and high-end piston market with volumetric scanning and 3D buffering. It’s intelligent enough to automatically scan, analyze and remove the ground clutter, plus provide automatic analysis for storm cell detection.
It’s also optimized for close-range scanning with the Watch feature, which identifies the shadowing effects of short-range cell activity by highlighting areas where radar signals are attenuated by heavy precipitation.
The dedicated weather radar page on the GTN 750Xi shows all of the GWX radar’s functions and modes, including icons for attenuation, turbulence, lightning prediction and detection and hail detection.
The new software also places a heading ring on the display that paints colors depicting weather that’s farther out from the first line of displayed storms.
Predictive wind shear is not an available function on the GTN or TXi displays and is airframe-specific when the GWX 8000 is installed in G1000/3000/5000-equipped aircraft.
Caring for the radome
It’s worth a few words on the importance of caring for aging radomes—an important system in any radar interface, and one that’s often ignored on aging aircraft. I’ve seen the radar troubleshooting
effort go in the wrong direction when a radar performance problem could have been solved with a radome repair. Shops consistently say that a big percentage of radar performance issues are traced to radome flaws, which the radar manufacturers have nothing to do with.
Don’t always judge a radome’s health by its appearance. They wear out by being in the line of aerodynamic fire—taking rain, sand, grit and high-velocity airflow on the chin. The surface paint and primer erodes, peels and cracks. Some suffer from hail damage. The typical radome is a honeycomb core, layered fore and aft with resin-impregnated fiberglass facings. It’s meant to be a durable and reliable shield for the pricey hardware that lives behind the dome.
“When you think about the microwave frequencies involved, a radome is like putting glasses on the radar. It needs to be as uniform and transparent as possible,” an engineer at Garmin advises. How about slapping a fresh layer of paint on the radome’s surface? Hold the spray gun. Paint selections—even when applied correctly—should be limited to approved neoprene, polyesters or polyurethane. Plain vanilla Rustoleum and most metallics aren’t recommended. But done right, we’ve heard that overhauling the radome can yield impressive gains in performance at longer ranges, in some cases improving the range from 70 miles to as much as 120 to 140 miles, depending on the radar and size of the array.
For starters, check the radome’s health by removing it from the aircraft. Pull it off and hold it in the sunlight. Since it’s translucent, look for consistent thickness, black spots, water streaks along the inside edge and any apparent cracks or punctures. Debonding of the surface appears as lighter areas around the edges of the honeycomb cells. Dumb it down and use the thin edge of a heavy coin to feel around. Tap the radome at various points on its surface.
You want to hear a sharp click because a duller thunk indicates that some of the laminations may have debonded or that water got into the honeycomb core.
Latest tech
With a 218-dB performance index (with a 10-inch antenna) and up to 320 nautical miles weather avoidance range (14-inch antenna), the $25,000 GWX 8000’s performance is at the top of the GA ship’s radar food chain. Unlike magnetron-equipped models, Garmin’s current line of radars use solid state tech, which promises much longer service life.
Better yet, Garmin’s latest display tech reduces workload when it’s perhaps at the highest.
See a demo of the GWX 8000/GTN 750 Xi.
For more, visit www.garmin.com.
