Use of Numerical Weather Prediction Analysis for Testing Pressure Altitude Measurements on Aircraft - An Application Example

Kurzfassung

Accurate static pressure measurements are essential for safe navigation. Aircraft static pressure measurements need to be calibrated and verified. We recently compared trailing cone static pressure measurements behind two different jet aircraft up to flight level 450 during 6 flights on different days with numerical weather prediction (NWP) data. The GNSS height above mean sea level measured during these flights is compared to NWP geopotential height. The NWP data were provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). The height differences at same pressure are 0.6±2.8 m on average. The corresponding pressure difference was determined to be -0.01±0.15 hPa. The method of comparing operational pressure/GNSS measurements on aircraft with NWP analysis or predictions can be used for testing the height keeping performance of aircraft after or during operation. Here we present an application example of the method. We show static pressure measured by research instruments on the German atmospheric research aircraft HALO compared to ECMWF analysis for 57 hours of data from an atmospheric research project over Europe in 2014. The method is used to derive corrected static pressure data. The corrected pressure also leads to a slightly better agreement between temperature measurements and ECMWF data which differed more when using the uncorrected pressure data as input for interpolation in the NWP data.