As mentioned above, while climbing or descending the expected flight path angle for the next 60nm is determined by the ratio of vertical speed to ground speed. When climbing, the top of the envelope is 4000 ft above this expected path. However, the lower boundary is 4000 ft below . of the expected angle. This provides a better view of “flight path” weather near the destination altitude should the pilot level off before the 60 nm point. The envelope boundaries are still subject to the limitations shown in the table above.
Similarly, when descending the lower boundary of the envelope is 4000 ft below the expected path, while the upper boundary is 4000 ft above . of the expected angle. Again, the envelope boundaries are subject to the limitations shown in the table above.
In AUTO mode, the RDR-4000 projects a three dimensional memory space onto a two dimensional display. This means the weather displayed for any one memory cell is the color of the strongest return in that column of memory cells. Specifically, if there is any weather data in a given column that is inside the envelope for "flight path" weather; the color of the strongest of these returns is displayed. If there is no weather data inside the envelope, then the color of the strongest return from outside the envelope is displayed as “secondary” weather.
Stronger returns outside the envelope ("secondary" weather) never override the strongest returns displayed as "flight path" weather.
MANUAL WEATHER ANALYSIS MODE (MAN): CONSTANT ALTITUDE
Constant altitude mode is an analysis mode providing a constant altitude slice throughout the entire 180-degree plan view. It is called constant altitude because the altitude slice extracted from the memory is corrected for the earth’s curvature. With traditional tilt angle settings the earth curves away from the beam far from the aircraft making it difficult to exactly measure the height of a cell. The Constant Altitude view provides a plan view that represents a thin slice through the volumetric memory of weather reflectivity data. This view is corrected for the curvature of the earth (i.e., it is a view at a constant MSL altitude level).
The altitude slice is selected by the ALT knob on the control panel. The altitude is selectable between zero and 60,000 ft in 1000 ft increments. Upon activation of the MAN mode, the slice at the current aircraft altitude (rounded to the nearest 1000 ft) is chosen. The view does not move up or down when the aircraft altitude changes. The pilot can quickly measure the tops of cells without any calculations. By varying the selected altitude until a cell just disappears, the cell height can be directly read from the display. The example below demonstrates the constant altitude mode. In the top center picture the system is in the AUTO mode at an aircraft altitude of 20,000 feet MSL. In the second center picture, MAN mode has been selected, so this is an altitude slice at the current aircraft altitude (20,000 feet MSL). The remaining pictures show the returns at different altitudes. Observe that the cell tops exceed 27,000 ft.
CONSTANT ALTITUDE MODE EXAMPLE USING VARYING ALTITUDES
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本文链接地址：WX RADAR RDR4000-PILOT GUIDE 气象雷达 RDR4000飞行员指南(16)
