Читать книгу Flight Theory and Aerodynamics - Joseph R. Badick - Страница 70

Using our example from the CAS discussion, EAS was determined to be 382.5 kts. If the outside air temperature at a pressure altitude of 20 000 ft is −30 °C, we can utilize Eq. 2.12 to find the TAS. From Table 2.1, the pressure ratio (δ) is 0.4595.

Figure 2.14 depicts the change in TAS between sea level and 15 000 ft when the IAS remains constant. For the respective IAS, the CAS calibration has been applied. As the aircraft climbs, the TAS increases as the air density decreases. The aircraft must travel at 130 kts. TAS to register 100 kts. on the airspeed indicator.

Understanding the relationship between the speeds above, and the calculation of each one, can be facilitated by remembering “ICE‐T.” IAS is read off the airspeed indicator, CAS is IAS corrected for installation/position errors, EAS is CAS corrected for compressibility, and finally TAS is EAS corrected for temperature and pressure.

Figure 2.14 IAS, CAS, and TAS comparison.

Source: U.S. Department of Transportation Federal Aviation Administration (2013).