To estimate fuel consumption and emissions of an aircraft in flight it is essential to know the thrust demanded by the aircraft, which has to be delivered by the engines, for any point fo the trip. An aircraft performance calculation provides this data, balancing all forces affecting the aircraft in flight (Lift, drag, thrust and weight, see figure 2). Some of these forces are dependent on the current weight of the aircraft, which in turn is dependent on the fuel consumption of the engines. As input data specific aircraft parameters and engine data -provided by the engine performance program- are needed to calculate the resulting accelerations and/or climb angles.
It is possible to recalculate given flight profiles with nearly any number of calculation points, including environmental impacts like wind or air temperature for each point of the flight mission. But even with relatively few calculation points, the approximation of a real flight mission is fairly good (Figure 3).
Author: Martin Plohr, DLR AT