Advanced Flight Planning and the Benefit of In-Flight Aircraft Trajectory Optimization

Abstract

The implementation of Trajectory-Based Operations, invented by the Single European Sky Air Traffic Management Research program SESAR, enables airlines to fly along optimized waypoint-less trajectories and accordingly to significantly increase the sustainability of the air transport system in a business with increasing environmental awareness. However, unsteady weather conditions and uncertain weather forecasts might induce the necessity to re-optimize the trajectory during the flight. By considering a re-optimization of the trajectory during the flight they further support air traffic control towards achieving precise air traffic flow management and, in consequence, an increase in airspace and airport capacity. However, the re-optimization leads to an increase in the operator and controller’s task loads which must be balanced with the benefit of the re-optimization. From this follows that operators need a decision support under which circumstances and how often a trajectory re-optimization should be carried out. Local numerical weather service providers issue hourly weather forecasts for the coming hour. Such weather data sets covering three months were used to re-optimize a daily A320 flight from Seattle to New York every hour and to calculate the effects of this re-optimization on fuel consumption and deviation from the filed path. Therefore, a simulation-based trajectory optimization tool was used. Fuel savings between 0.5% and 7% per flight were achieved despite minor differences in wind speed between two consecutive weather forecasts in the order of 0.5 m s−1. The calculated lateral deviations from the filed path within 1 nautical mile were always very small. Thus, the method could be easily implemented in current flight operations. The developed performance indicators could help operators to evaluate the re-optimization and to initiate its activation as a new flight plan accordingly.

Implementation of a Long-Range Air Traffic Flow Management for the Asia-Pacific Region

“…Operators and flight planning tools are continuously implementing a function to dynamically react to changes in the boundary conditions of flight planning [64], [65]. These dynamic adjustments of aircraft routes enable to appropriately react to actual environmental and traffic conditions [66]. Thereby, the main focus either lays on the uncertainty of the significant parameter for efficient flight planning, which could be wind [67], [68], or on safety issues for the prediction of turbulence cells [69].…”

“…Aircraft speed could be set between optimal cruise speed and minimum fuel consumption, and speed control may affect the fuel consumption of the aircraft (maximum speed reduction during cruise phase is around the 7% [75]). Thus airline's cost index must be included in delay mitigation strategies [66]. But even in-flight trajectory optimization could already lead to fuel savings of about 0.5%-7% [8] and thus may also improve delay situations if efficiently integrated into ATFM [73].…”

Fundamental Framework to Plan 4D Robust Descent Trajectories for Uncertainties in Weather Prediction

“…Studies on simulating and optimizing descent trajectories, which eventually lead to CDO trajectories, have been carried out intensively in the last decade [11,13,14]. The necessity of re-optimizing trajectories has also been raised in [15][16][17][18][19] by examining the deviation of an aircraft's energy state from the planned reference trajectory as a useful trigger. However, to the best of the authors' knowledge, these prior works assumed deterministic scenarios and ignored the impacts of uncertainties.…”

Importance of Weather Conditions in a Flight Corridor

“…Meteorological data are provided by the Global Forecast System (GFS) (https://www. ncei.noaa.gov/products/weather-climate-models/global-forecast (accessed on 31 August 2020)), which combines data from various sources and produces forecasts of meteorological parameters such as temperature, wind speed, and wind direction [6]. GFS data are produced by the National Centers for Environmental Prediction (NCEP), a branch of the National Oceanic and Atmospheric Administration (NOAA).…”