Interplay of unsteady aerodynamics and flight dynamics of transport aircraft in icing conditions

Abstract

Airframe icing causes significant degradation of aerodynamic characteristics and influences the flight safety. Wind tunnel study of longitudinal steady and unsteady aerodynamic characteristics of a transport aircraft in icing conditions is carried out in order to develop mathematical model of aerodynamics in the extended flight envelope. The wind tunnel results are validated through flight tests conducted for the real aircraft. Large, glaze-horn ice shapes, corresponding to holding flight phase, are considered.Influence of an ice protection system as well as its failure is examined. Effect of icing on the unsteady aerodynamics characteristics is studied not only through wind tunnel tests but also via analysis of subsequent influence on the flight dynamics of the aircraft. The conducted study shows that the ice shapes of the holding phase leads to reduced stall angle of attack (AoA), maximum lift, and longitudinal damping. Flight dynamics analysis demonstrates that dangerous aircraft behaviour in the form of high AoA departure and limit cycle oscillations (LCO) can be observed at smaller elevator deflections for the iced aircraft. Taking into account icing influence on the unsteady aerodynamics in the flight dynamics simulations revealed degradation of the dynamic response and deterioration of phase portraits of the system. Even for small AoA and elevator deflection the aircraft might be trapped into the basin of attraction of high-AoA LCO. In addition, incorporating icing effects in unsteady aerodynamics manifest larger amplitude of LCO.

Risk Quantification and Visualization Method for Loss-of-Control Scenarios in Flight

“…Therefore, it is appropriate to use the six-degree-of-freedom (six-DOF) equations to simulate the dynamic response of the aircraft [37]. When the aircraft encounters failure problems, variables and coefficients in its six-DOF equations must be modified according to Equations ( 1)- (7). As the flight risk analysis method combining risk quantitative assessment and visual deduction is the core of the study, the model of rigid aircraft motion will not be discussed further in this study.…”

“…Gumusboga et al [6] developed a comprehensive flight dynamics model of aircraft with control surface failures. Ignatyev et al [7] used a combination of wind tunnel tests and flight simulation to investigate the interplay of aerodynamics and flight dynamics in icing conditions. The flight envelope defines the safe boundaries within which an aircraft may be flown and recovered [8,9].…”

Capturing nonlinear time-dependent aircraft dynamics using a wind tunnel manoeuvre rig

“…Note that forced-oscillation experiments can be conducted using the model control surfaces to acquire dynamic stability derivatives [6,43], as well as unsteady aerodynamic characteristics [17].…”

“…An alternative way of studying the LCO behaviour is by presenting the system steady state dynamics in the form a bifurcation diagram. Note that equilibrium (fixed-point) solutions shown in bifurcation diagrams may be regarded as trimming points [17]. For an overview on bifurcation theory and its application to aircraft dynamics analysis the reader is referred to Goman et al [14], Thompson and Macmillen (eds.)…”

“…More recently, the lift and drag forces of a generic unmanned combat air vehicle were characterised using static and forced oscillation testing and then compared to CFD results by Cummings et al working at the Department of Aeronautics at the USAF [9]. In the Central Aerohydrodynamic Institute (TsAGI) in Russia, wind tunnel experiments were carried out to investigate the effect of icing on the longitudinal steady and unsteady aerodynamic characteristics of an aircraft model [17]. In the Lu Shijia Laboratory at the Beihang University in China, the aerodynamic characteristics of a delta wing at high angles of attack were studied through pitching oscillation experiments in a water channel [51].…”