Abstract: The propulsive and aerodynamic forces acting upon an airborne vehicle are functions of the pressure, density, and temperature of the air through which the vehicle is traveling. Flight testing, therefore, requires precise measurements of these properties in order to provide accurate predictions of aircraft performance. Aircraft air data systems generally include pitot-static systems and total temperature probes which measure free stream static pressure, total pressure, and total temperature. However, these measurements include errors for which corrections must be applied. The purpose of this text is to provide an understanding of pitot-static theory and the process for determining pitot-static and temperature errors through air data system calibration flight testing. Before discussing pitot-static theory, we should first have a basic understanding of the atmosphere in which we fly. The properties of the atmosphere have a daily, seasonal, and geographic dependence and, in fact, are constantly changing. Solar radiation and weather patterns can cause rapid and significant local variations in the atmosphere. It is not practical to account for these variations when considering the performance of flight vehicles. Therefore, an atmospheric model was developed to provide a common reference based on mean or "standard day" values of the atmospheric properties at each altitude. This model, called the standard atmosphere, allows us to relate theoretical predictions, wind tunnel data, and flight test data. Through it, test data collected on a 'non-standard' or 'test' day can be corrected to standard day, and flight manual charts can include corrections to predict performance on any given day.
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Pages: |
86 |
| Report Date: |
JAN 96 |
| Report Number: |
A612023 |
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