| Notso Fantastic |
14th Apr 2003 17:50 |
Set about 5 deg Up for T/O. During climb, progressively lower to zero, then during cruise, tilt slightly down (the reference is automatically to the horizon, not aeroplane attitude- it is gyro stabilised). The beam is a narrow pencil beam that sweeps between almost 90 degrees either side and beam width about 1 1/2 degrees, so you don't want too much in the way of ground returns, about 1 to 11/2 degrees tilt down is about right. That way, any storms below you will show up some distance away before you fly over them unaware. If you tilt too far down, you will see storms closer, but ground returns will gradually encroach the steeper down you look, appearing as a very solid semicircular shape. You do get fairly good at distinguishing weather from ground returns. The mountain shapes on radar can look peculiar- you only see the side of terrain that is being 'illuminated' by the radar. As you descend, ground returns will progressively move in, so you have to tilt the beam higher to sweep the sky in front and still sweep the weather below you. On final approach, it's a good idea to be tilting up to 5 degrees up for the go-around case. As well as a traditional radar display, modern aeroplanes allow you to overlay the radar display onto the Navigation display, so you can see exactly where the weather is in relation to your intended route and the waypoints and navigation displays- very clever and convenient. Radar useful range seems to be about 120-150 miles at cruise altitude and less lower down where ground clutter seems to affect useful range. Does that answer?
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