Equations of Motion for a High Performance Fighter A Simplified Dynamical Model Based on Elementary Physics
F18 Hornet - High Performance Fighter - How do we model such a system?
Simplified Aircraft Schematic Note: Aircraft is unstable iff i.e. c.g. aft of c.p. produces “pitch-up instability” Instability desirable for increased maneuverability (high-g maneuvers) - High Performance Fighter
Aircraft Parameters Fuselage damping coefficient: Lift produces cw moment: - Lift coefficient: - Lift moment arm can be +/- Elevator produces ccw moment: - Elevator coefficient: - Typically - High Performance Fighter
Aircraft Pitch Angle Dynamics Moment from control surface (elevator) deflection (CCW) Moment from lift force (CW) Fuselage rotational damping moment (CW) - Apply Newton’s 2 nd Law of Motion Moment of inertia
Aircraft Pitch Angle Dynamics Elevator term substitution: Lift term substitution: - Capture effect of elevator and lift
Aircraft Pitch Angle Dynamics - Rewrite 2 nd Order Ordinary Differential Equation (ODE) in standard form.