Page 17 - June 2015 Volume 19 Number 6

matter between their ears to be pilots in the first place.)
The GWX 70 has another feature that taps into Doppler: “Altitude Compensated Tilt”. No doubt, it will be made much of by Garmin salespersons, but it’s not just worthless, but misleading. Actually, all radars have “Auto Tilt” – a “Parked Position”, as it were. It’s simply with Tilt set at 0o with 10 and 12-inch antennas and -1o with an 18-inch one. (Incidentally, Garmin’s “ACT” requires a GPS input to function.) It’s called the “parked” position for tilt and is
dropping on your head. Don’t ever fly under it. Of all the gizmos that have been added to radars over the years, VP is the only feature that actually increases safety.
Another very useful carry-over from older radars is Sector Scan, which has been around for eons. But, beginning with their earlier GWX 68 radar, Garmin added an enhancement that makes it 10 times more useful than in pre- 21st Century times. That feature is now carried over to the GWX 70 as “Variable Sector Scan”, meaning you can cause it to scan a
guys and gals. Garmin’s version of Sector Scan is a bravo addition.
In a left-handed sort of way, Garmin’s engineers also deserve a big thanks for making it simple to overcome a major fault on all the newest radars. Missing on the GWX 70 is magenta symbology, to indicate an extremely vicious storm. That’s no fault of Garmin’s. Ten or so years ago, an FAA/RTCA Committee, most likely egged on by radar manufacturers’ legal departments, decreed that magenta may not be used to warn pilots of extreme hazards. Why? Because it’s needed
necessary to see radar sh
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where the storms are rel
terrain objects.
The GWX 70 has “Extended Range STC”, adopted from the ancient Sperry line, another ancient engineering hocus-pocus that’s simply a reduction, a miscalibration, in the thresholds for the colors beyond 40 or so miles. The result is red echoes that aren’t really red now but will be when you get closer to them. It’s of benefit only for ill-trained pilots who don’t understand that radar energy gets weaker
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o know there’s a hazard and
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urn tail. But pilots must also
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now what degree and kind
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f hazard a storm presents.
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Without that knowledge, how
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re they to decide how much
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rcumnavigation distance
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prudent?
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act is, when you see red
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ly that it’s raining, period.
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must know if it’s just light rain
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the greater the distance f
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ly rain, or is it water turned
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the source, just like a lig
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ilstones? If the latter, are the
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dimmer the greater the d
from its source.
GWX 70 engineers did pick up a major safety feature along the way: Vertical Profile, an innovation added at Bendix/King in about 1985 and picked up by Garmin for its GWX 68 and 70. VP may be the most valuable new radar feature since flat-plate antennas. Scanning the vertical structure of a storm reveals much about the hazards within it. For example, when there is an echo aloft but nothing below it, or only a weak return down low, you’re looking at a very high risk of having millions of tons of water suddenly
JUNE 2015
d
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eh
p p
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nes small or large? The old
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a, now seen only in course
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n your EHSI, revealed all that. But, the bureaucrats have taken it away from us.
Fortunately, there’s a way to fool the GWX 70’s four-color display into revealing all those critical facts about a thunderstorm. Since radar engineers mess with color calibration to achieve “Extended Range STC,” pilots can do a similar thing to switch the mandated four colors into, in effect, five colors. (Bless the Garmin engineers for making it so easy with their CAL control and display.) The GMX 70
l
li
in
ne
o
but the ability to choose a Sector Scan down to only 20o and to move it to any of many different sectors is outstanding.
For starters, Sector Scan results in a greatly-increased display update rate. Helicopter operators, who tend to use radar more for navigation than for weather, will just about swoon over it on rainy, foggy nights when trying to pick up a hospital rooftop. And it’ll make navigating to the landing pad on an offshore rig much less sweaty for the petroleum
TWIN & TURBINE • 15