10.19 indicate where it was judged that measurements were not required. This is often an easy judgement to make for temperature assessments but less so for downdraft and turbulence. Consequently for downdraft and turbulence measurements, a full range of wind direction should be tested.
For temperature rise measurements, results should be presented for a range of reference wind speeds e.g. 5, 10, 15 and 20 m/s. This is because temperature rise has an unpredictable dependence on reference wind speed. In contrast, downdraft and turbulence can be re-scaled for any wind speed. For this re-scaling, a reference wind speed of 25 m/s, taken to be a practical upper limit for helicopter operation, is suggested.
To supplement the tables, it is recommended that the lateral survey results be presented also as a contour plot as shown in Figure 10.21.
To highlight the wind conditions in which design criteria are exceeded it is recommended that summary data be presented to provide an immediate visual indication. Examples of such presentations for downdraft, temperature rise and turbulence data are shown respectively in Figures 10.22, 10.23 and 10.24. In these figures, the radial axis is the reference wind speed and the circumference axis denotes wind direction (from), with respect to Platform North. The absence of shading indicates compliance with the criteria.
Wind speed at 10 m = 5 m/s
Wind direction (degrees from Platform N) z (m) 5 z (m) 10 Z (m) 15 z (m) 20 z (m) 25 z (m) 30 MAX
3 - second peak temperature °C
0
15
30 5.2 4.3 8.6 5.9 0.1 0.1 8.6
45 11.8 8.3 9.3 4.1 0.1 0.1 11.8
60 9.7 8.3 8.8 5.5 0.3 0.4 9.7
75 3.4 2.2 5.1 2.2 0.3 0.2 5.1
90
105
120
135
150
165 0.5 0.4 0.3 0.0 0.0 0.0 0.5
180 1.9 1.5 1.6 0.2 0.0 0.0 1.9
195 1.1 1.1 1.0 0.0 0.0 0.0 1.1
210 0.9 0.9 0.7 0.0 0.0 0.0 0.9
225 0.0 0.0 0.0 0.0 0.0 0.0 0.0
240
255
270
285
300
315
330
345
Figure 10.19 - Polar Scan of 3 second peak temperature rise above landing spot
NOTE: Empty cells denote where measurements were judged to be unnecessary.
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