Page 14 - Volume 18 Number 2

RadarBy Archie Trammell When I conduct radar-training programs, thefirst question is, invariably, “Where do I put the TILT?” That confusion is a deep mystery to anyone who understands what TILT does. It simply controls the vertical slice of the atmosphere depicted on a radar’s display. What’s below the sweep of the beam is ignored, what’s at and above the bottom of the beam is detected and displayed. It’s justthat simple.Therefore, just three TILT positions are required for safety on every flight, from takeoff to touchdown, summer and winter, anywhere in the world. I call them TIP, NAP and TUT.TIP is with the bottom of the beam level, NAP is with the bottom of the beam sloped down 4o, and TUT is with the center of the beam pointed up 10o. Once it’s determined where each is, TILT management becomes so simple even an eight-year old can be taught it, with a 10-minute demonstration. And those TILT positions have to be determined only once in your aircraft, assuming an antenna stabilization system.Here’s how:TIP is the “Threat Identification Position”. To repeat, a radar doesn’t detect and display anything below the bottom of the beam, therefore TIP is simply with the bottom of the beam sweeping level to the earth, as in figure 1. To select it, first note your altitude in thousands of feet AGL. For example, assume 15,000 AGL; adjust TILT so the bottom of the beam is sweeping on the ground at 15 nm, as close as you can get it.It’ll look like this photo.Here, the terrain to the left is lower, so I couldn’t get the bottom of the beam on the 15 nm arc over on the right, but the remainder is right on 15 nm, allowing for slight terrain undulations. Also, sweep-to-sweep, it’ll wander out and in a bit; STAB systems are never perfect, so just average it out. When you have it, note the TILT indication.Here, it’s on -4o.From there, increase TILT 8o, as in this lower photo ; from -4o to + 4o.That’s TIP. The bottom of the beam is sweeping level at 15,000 feet, so that cluster of echoes out there 18 to 22 nm is weather, no question.Again, note your altitude AGL in thousands of feet, put the bottom of the beam on this “Range”, increase TILT 8o and that’s TIP. Once TIP is determined, +4o on this radar, that setting will always be TIP, whether flying at 2,000 feet or 20,000. It’ll probably be different on your radar, but once determined, that indicated TILT will always be TIP for your radar, regardless of altitude. It should be used often when flying below 20,000, but never left in that position for more than a few sweeps. Otherwise, a storm may shoot up from below and zap you, which is the number-one cause of turbulence injuries in the airlines.To prevent shoot-up from occurring, select NAP. How? Simply reduce TILT from TIP by 4o. Obviously, that will result in the bottom edge of the beam being sloped down 4o, as illustrated in figureFigure 1Tilt Management12 • TWIN & TURBINEFEBRUARY 2014Tilt