"Preface Flight mechanics lies at the heart of aeronautics. It is the point of confluence of other disciplines within aerospace engineering and the gateway to aircraft design. Almost every curriculum in aerospace engineering includes two courses in flight mechanics--one on applied aerodynamics and airplane performance and the other on airplane stability/control and flight dynamics. Having taught both these subjects for over two decades, the authors' experience can be summed up briefly in the following student response: 'These are the best subjects in the curriculum. When you teach it in class, everything is obvious, but when we go back and read the textbook, things get very confusing'. As we got down to decoding this statement, several questions emerged: - Why put students through the gruesome derivation of the sixdegree- of-freedom equations early in the course, preceded by the axis transformations, and followed by the small perturbation math, when the bulk of the course is focussed on the dynamic modes about straight and level flight trim, which can be easily presented without going this route? - Would it not be nicer to write the equations for the second-order modes in a manner similar to a spring-mass-damper system? Then, one could read off the stiffness and damping directly, which would also give the conditions for stability. - The definitions of 'static' and 'dynamic' stability have been the cause of much student heartbreak. With the second-order form of the equations, the requirement of positive stiffness is the same as the socalled 'static' stability condition, so why not drop the separate notion of static stability entirely? -"-- Read more...
Abstract: "Preface Flight mechanics lies at the heart of aeronautics. It is the point of confluence of other disciplines within aerospace engineering and the gateway to aircraft design. Almost every curriculum in aerospace engineering includes two courses in flight mechanics--one on applied aerodynamics and airplane performance and the other on airplane stability/control and flight dynamics. Having taught both these subjects for over two decades, the authors' experience can be summed up briefly in the following student response: 'These are the best subjects in the curriculum. When you teach it in class, everything is obvious, but when we go back and read the textbook, things get very confusing'. As we got down to decoding this statement, several questions emerged: - Why put students through the gruesome derivation of the sixdegree- of-freedom equations early in the course, preceded by the axis transformations, and followed by the small perturbation math, when the bulk of the course is focussed on the dynamic modes about straight and level flight trim, which can be easily presented without going this route? - Would it not be nicer to write the equations for the second-order modes in a manner similar to a spring-mass-damper system? Then, one could read off the stiffness and damping directly, which would also give the conditions for stability. - The definitions of 'static' and 'dynamic' stability have been the cause of much student heartbreak. With the second-order form of the equations, the requirement of positive stiffness is the same as the socalled 'static' stability condition, so why not drop the separate notion of static stability entirely? -"
Content: Introduction What, Why and How? Aircraft as a Rigid Body Six Degrees of Freedom Position, Velocity and Angles Aircraft Motion in Wind Longitudinal Flight Dynamics Longitudinal Dynamics Equations A Question of Timescales Longitudinal Trim Aerodynamic Coefficients CD, CL, Cm Wing-Body Trim Stability Concept Linear First-Order System Linear Second-Order System Nonlinear Second-Order System Pitch Dynamics about Level Flight Trim Modelling Small-Perturbation Aerodynamics Pitch Dynamics about Level Flight Trim (Contd.) Short-Period Frequency and Damping Forced Response Response to Pitch Control Longitudinal Trim and Stability Wing-Body Trim and Stability Wing-Body Plus Tail: Physical Arguments Wing-Body Plus Tail: Math Model Role of Downwash Neutral Point Replacing VH with VH / Effect of CG Movement Rear CG Limit due to Airplane Loading and Configuration at Take-Off Cm, CL Curves-Non-Linearities Longitudinal Control All-Moving Tail Elevator Tail Lift with Elevator Airplane Lift Coefficient with Elevator Airplane Pitching Moment Coefficient with Elevator Elevator Influence on Trim and Stability Longitudinal Manoeuvres with the Elevator Most Forward CG Limit NP Determination from Flight Tests Effect of NP Shift with Mach Number Long-Period (Phugoid) Dynamics Phugoid Mode Equations Energy Phugoid Mode Physics Phugoid Small-Perturbation Equations Aerodynamic Modelling with Mach Number Phugoid Dynamics Phugoid Mode Frequency and Damping Accurate Short-Period and Phugoid Approximations Derivative CmMa Derivative Cmq1 in Pitching Motion Derivative Cmq1 in Phugoid Motion Flow Curvature Effects Lateral-Directional Motion Review Directional Disturbance Angles Directional versus Longitudinal Flight Lateral Disturbance Angles Lateral-Directional Rate Variables Small-Perturbation Lateral-Directional Equations Lateral-Directional Timescales Lateral-Directional Aerodynamic Derivatives Lateral-Directional Small-Perturbation Equations (Contd.)... 202 Lateral-Directional Dynamics Modes Lateral-Directional Dynamic Modes Roll (Rate) Mode Roll Damping Derivative Clp2 Roll Control Aileron Control Derivative, Cldeltaa Yaw due to Roll Control Aileron Input for a Bank Angle Dutch Roll Mode Directional Derivatives CYss and Cnss Lateral Derivative: Clss Damping Derivatives: Cnr1 and Clr1 Rudder Control Spiral Mode Real-Life Airplane Data Computational Flight Dynamics Aircraft Equations of Motion Derivation of Aircraft Equations of Motion 3-2-1 Rule Derivation of Aircraft Equations of Motion (Contd.) Numerical Analysis of Aircraft Motions Standard Bifurcation Analysis Extended Bifurcation Analysis
