Читать книгу Flight Theory and Aerodynamics - Joseph R. Badick - Страница 68

Equivalent airspeed (EAS) results when the CAS has been corrected for compressibility effects. Figure 2.12 shows a compressibility correction chart. In general, if flying above 10 000 ft and 200 kts., the compressibility correction should be made. Unlike the instrument and position error charts, which vary with different aircraft, this chart is good for any aircraft.

EAS is not a significant factor in airspeed computations when aircraft fly at relatively low speeds and altitudes, but at higher speeds and altitudes, the compressibility correction must be taken into account. For example, if an aircraft is flying at a pressure altitude of 20 000 ft at a CAS of 400 kts., Figure 2.12 indicates a compressibility correction of −17.5 kts. The EAS for this example is 382.5 kts.

Figure 2.12 Compressibility correction chart.