American Institute of Aeronautics and Astronautics 1 Analysis of the Impact of Performance Model Accuracy on 4D Trajectory Optimization M. Battipede * , G. Sirigu † , M. Cassaro ‡ , and P. Gili § Politecnico di Torino, Torino, ITALY, 10129 4D trajectory optimization can be conceived as a non-linear optimization problem, where the mathematical formulations adopted to generate and evaluate trajectories are purposely selected to meet the specific operational requirements, which are recognized as primary for each mission phase. Among the mathematical tools, the choice of the optimization technique and the objective function is always thoroughly addressed in literature. Among the available aircraft mathematical models, the more attractive solutions for trajectory optimization are the so called performance models, due to their great accuracy in describing the real aircraft behavior conjugated with the possibility of being integrated in the mathematical tool in a very straightforward way. This paper aims to investigate how a trajectory optimization problem is affected by the accuracy of the employed model in terms of resulting velocities, accelerations and angles demanded. Nomenclature C = path constraint D = differentiation matrix D = drag E = East direction coordinate f = state vector derivative function FF = fuel flow g = gravitational acceleration h = altitude J = cost function L = cost function Lagrange term m = aircraft mass N = North direction coordinate Nc = number of control variables Np = interpolating polynomial order Ns = number of state variables P = waypoint s = actual aircraft position SEP = specific excess power T = thrust t = time u(t) = control function VTAS = true air speed w = Clenshaw-Curtis weights x(t) = state variables γ = path angle ε = waypoint error * Associate Professor, Mechanical Aeronautical and Space Dept., manuela.battipede@polito.it, AIAA Member. † Ph.D. Student, Mechanical Aeronautical and Space Dept., giuseppe.sirigu@polito.it. ‡ Ph.D. Student, Mechanical Aeronautical and Space Dept., mario.cassaro@polito.it. § Associate Professor, Mechanical Aeronautical and Space Dept., piero.gili@polito.it, AIAA Member.