Forecasts of wind in the upper atmosphere are used quantitatively for flight planning. The calculated flight times are derived directly from the numerical wind data, together with route and aircraft information. Existing studies show that considerable benefits would stem from higher accuracy of weather forecasting, such as the opportunity to carry a smaller contingency of fuel on aircraft (reducing fuel use).
The overall objective of MICA was to determine the importance of accurate weather forecasting in developing and maintaining a four-dimensional model of a flight, in particular, focusing on the use of computer-based controller assistance tools in operational air traffic control (ATC). Specific objectives were to:
- identify potential improvements in the quality of predictions;
- analyse trends in weather forecasting techniques;
- define operational requirements for future trajectory-based decision support tools;
- propose a functional architecture whereby meteorological data can be made available for integration into trajectory-based decision support;
- apply sensitivity analysis methods to identify the importance of weather information in the formulation of the trajectory.
A number of meteorological conditions can affect an aircraft’s trajectory and trajectory prediction. MICA has made recommendations about the influence that some meteorological conditions can have on trajectory and ground speed prediction:
- Wind during cruise, climb and descent, and wind shear effects of a trough during cruise. Ground speed errors mainly depend on wind speed, while trajectory prediction errors mainly depend on the angle between route direction and trough axis. Errors in wind speed and direction forecasts are non-linear with respect to altitude, so the prediction errors also exhibit a non-linear dependence on prediction time.
- Temperature effects during cruise and climb and for a front during cruise.
- The higher the altitude of flight and the faster the aircraft speed, the larger the deviation errors. The smaller the angle between aircraft heading and the front axis, the larger the prediction error. Furthermore, the dependence of ground speed prediction errors on forecasted temperature inversion during climb is almost linear.
- Cloud during descent.
- Large cloud layers have a significant impact on the prediction of descent if no forecast is used.
The project has highlighted the need for developing methodologies that are more accurate to predict an aircraft’s trajectory. European ATC systems are affected because this could improve both the performance and the capacity of the air transport system.