Fuel consumption assessment for speed variation concepts during the cruise phase

In recent years, some research studies in Air Traffic Management (ATM) have proposed the idea of adjusting the speed of aircraft for several applications, like for instance, conflict resolution, 4D trajectory management, and airspace capacity and demand balance. In this paper an initial assessment on how this kind of speed variations may affect to fuel consumption is presented. Only the cruise phase is considered and the relationships existing among different variables such as the speed, the flight level, the aircraft mass etc. are arisen. In addition, it is emphasised in what conditions a speed reduction strategy can be implemented without penalising the fuel consumption. Thence, it is shown that there is a range of speeds, lower than the nominal cruise speed, that do not suppose an increase in fuel consumption regarding the nominal block fuel. However, a certain sensibility with the selected Cost Index is identified. High values of the Cost Index allow more speed margin without a negative fuel impact, while low values of the Cost Index reduce the impact on fuel consumption in the case the nominal cruise speed is increased.