ratio, θ
Speed of sound (kts.)
|
Kinematic viscosity, v (ft2/s)
|
|
0
|
1.0000
|
1.0000
|
1.0000
|
59.00
|
1.0000
|
661.7
|
0.000 158
|
|
1 000
|
0.9711
|
0.9854
|
0.9644
|
55.43
|
0.9931
|
659.5
|
0.000 161
|
|
2 000
|
0.9428
|
0.9710
|
0.9298
|
51.87
|
0.9862
|
657.2
|
0.000 165
|
|
3 000
|
0.9151
|
0.9566
|
0.8962
|
48.30
|
0.9794
|
654.9
|
0.000 169
|
|
4 000
|
0.8881
|
0.9424
|
0.8637
|
44.74
|
0.9725
|
652.6
|
0.000 174
|
|
5 000
|
0.8617
|
0.9283
|
0.8320
|
41.17
|
0.9656
|
650.3
|
0.000 178
|
|
6 000
|
0.8359
|
0.9143
|
0.8014
|
37.60
|
0.9587
|
647.9
|
0.000 182
|
|
7 000
|
0.8106
|
0.9004
|
0.7716
|
34.04
|
0.9519
|
645.6
|
0.000 187
|
|
8 000
|
0.7860
|
0.8866
|
0.7428
|
30.47
|
0.9450
|
643.3
|
0.000 192
|
|
9 000
|
0.7620
|
0.8729
|
0.7148
|
26.90
|
0.9381
|
640.9
|
0.000 197
|
|
10 000
|
0.7385
|
0.8593
|
0.6877
|
23.34
|
0.9312
|
638.6
|
0.000 202
|
|
15 000
|
0.6292
|
0.7932
|
0.5643
|
5.51
|
0.8969
|
626.7
|
0.000 229
|
|
20 000
|
0.5328
|
0.7299
|
0.4595
|
−12.32
|
0.8625
|
614.6
|
0.000 262
|
|
25 000
|
0.4481
|
0.6694
|
0.3711
|
−30.15
|
0.8281
|
602.2
|
0.000 302
|
|
30 000
|
0.3741
|
0.6117
|
0.2970
|
−47.98
|
0.7937
|
589.5
|
0.000 349
|
|
35 000
|
0.3099
|
0.5567
|
0.2353
|
−65.82
|
0.7594
|
576.6
|
0.000 405
|
|
36 089a
|
0.2971
|
0.5450
|
0.2234
|
−69.70
|
0.7519
|
573.8
|
0.000 419
|
|
40 000
|
0.2462
|
0.4962
|
0.1851
|
−69.70
|
0.7519
|
573.8
|
0.000 506
|
|
45 000
|
0.1936
|
0.4400
|
0.1455
|
−69.70
|
0.7519
|
573.8
|
0.000 643
|
|
50 000
|
0.1522
|
0.3002
|
0.1145
|
−69.70
|
0.7519
|
573.8
|
0.000 818
|
a The tropopause.
ALTITUDE MEASUREMENT
When a pilot uses the term altitude, the reference is usually to altitude above sea level as read on the altimeter, but it is important that the distinction is made to understand what types of altitude exist. When meteorologists refer to the height of the cloud layer above an airfield, they are usually referring to the altitude above the field elevation. When air traffic control refers to an altitude at FL180 and above, they are referring to pressure altitude. A flight crew in an aircraft approaching the runway during a low ceiling CAT III instrument approach will need to understand the value of a radar altimeter. Understanding what “altitudes” are important at different periods of flight, and the effect of temperature, pressure, and moisture on those altitudes, is imperative for safe flight.
