Trim Analysis of Nonlinear Flight Dynamics for a Civil Aircraft with Active High-Lift System

Abstract

This paper shows recent flight mechanical simulation results of a civil active highlift aircraft with blown Coand˘a flaps. The main focus lies on the trim analysis of the aircraft. To this end the basic structure and core elements of the nonlinear model, describing the dynamic behavior of an aircraft with this specific type of active highlift system, are presented. The center of gravity location range allowing controllability and static stability of the aircraft is determined, followed by an analysis of the resulting characteristics of the aerodynamic model and their impact on the trim results of the aircraft. The results show specific flight mechanical difficulties due to the active highlift system, namely characteristics hardly compatible with safe takeoff and approach procedures. The physical explanations will be given and discussed. The necessity of the application of a wing leading edge device is pointed out by preliminary studies and further remedial means are proposed.