PRIMUSr 880 Digital Weather Radar System
Step | Procedure |
5When flying at high altitudes, tilt downward frequently to avoid flying above storm tops.
Studies by the National Severe Storms Laboratory (NSSL) of Oklahoma have determined that thunderstorms extending to 60,000 ft show little variation of turbulence intensity with altitude.
Ice crystals are poor reflectors. Rain water at the lower altitudes produce a strong echo, however at higher altitudes, the nonreflective ice produces a week echo as the antenna is tilted up. Therefore, though the intensity of the echo diminishes with altitude, it does not mean the severity of the turbulence has diminished.
NOTE: If the TILT control is left in a fixed position at the higher flight levels, a storm detected at long range can appear to become weaker and actually disappear as it is approached. This occurs because the storm cell which was fully within the beam at 100 NM gradually passes out of and under the radar beam.
6When flying at low altitudes rotate tilt upward frequently to avoid flying under a thunderstorm. There is some evidence that maximum turbulence exists at middle heights in storms (20,000 to 30,000 ft); however, turbulence beneath a storm is not to be minimized. However, the lower altitude may be affected by strong outflow winds and severe turbulence where thunderstorms are present. The same turbulence considerations that apply to high altitude flight near storms apply to low altitude flight.
7Avoid all rapidly moving echoes by 20 miles. A single thunderstorm echo, a line of echoes, or a cluster of echoes moving 40 knots or more will often contain severe weather. Although nearby, slower moving echoes may contain more intense aviation hazards, all rapidly moving echoes warrant close observation. Fast moving, broken to solid line echoes are particularly disruptive to aircraft operations.
8Avoid, the entire cell if any portion of the cell is red or magenta by 20 NM.
The stronger the radar return, the greater the frequency and severity of turbulence and hail.
Severe Weather Avoidance Procedures
Table 5- 12 (cont)
A28- 1146- 102- 00 | Radar Facts |
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