Procedures and specifications for numerical analysis and flight check

The purpose of most of the numerical analysis is to predict in advance the performance of the ILS-subsystem and to determine the installation parameters. The purpose of the flight check is to verify the performance of the installed system.

By this it is necessary that both procedures are working with the same specifications and essentially the same boundary conditions. Annex 10 and DOC 8071 seem to guarantee this target.

The error sources in both procedures are very much different. If the numerical model is realistic and physically adequate, the accuracy of the results is high using modern tridimensional methods /1/. This is especially for the glidepath on tridimensional smoothly curved ground. As a result, the accuracy is probably higher than for the flight check verification procedure.

In the flight check procedure, specific errors are involved as encountered for a number of flight check cases

• flight technical errors especially during windy conditions
• hardware calibration errors (e.g. filters, aircraft-antenna, specific receiver problems /4/, filter delay problems, aircraft antenna effects)
• software correction problems (e.g. incorrect compensation of aircraft movement during measurements)
• geometrical reference errors (e.g. by incorrect commands of the pilot, errors by the reference of the positioning system)
• receiver problems generating technical artefacts /4/.