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In many flight dynamics applications, the Earth frame is assumed to be inertial with a flat x E,y E-plane, though the Earth frame can also be considered a spherical coordinate system with origin at the center of the Earth. The other two reference frames are body-fixed, with origins moving along with the aircraft, typically at the center of gravity.
Flight dynamics is the science of air-vehicle orientation and control in three dimensions. The critical flight dynamics parameters are the angles of rotation with respect to the three aircraft's principal axes about its center of gravity, known as roll, pitch and yaw.
Most aircraft trimmed for straight-and-level flight, if flown stick-fixed, will eventually develop a tightening spiral-dive. [2] If a spiral dive is entered unintentionally, the result can be fatal. A spiral dive is not a spin; it starts, not with a stall or from torque, but with a random perturbation, increasing roll and airspeed.
Babister A W: Aircraft Dynamic Stability and Response. Elsever 1980, ISBN 0-08-024768-7; Friedland B: Control System Design. McGraw-Hill Book Company 1987. ISBN 0-07-100420-3; Roskam Jan: Airplane Flight Dynamics and Automatic Flight Controls. Roskam Aviation and Engineering Corporation 1979. Second Printing 1982.
Aircraft flight mechanics are relevant to fixed wing (gliders, aeroplanes) and rotary wing (helicopters) aircraft. An aeroplane ( airplane in US usage), is defined in ICAO Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".
In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under given flight conditions. The L/D ratio for any given body will vary according to these flight conditions.
Pitching moment changes pitch angle A graph showing coefficient of pitching moment with respect to angle of attack for an airplane.. In aerodynamics, the pitching moment on an airfoil is the moment (or torque) produced by the aerodynamic force on the airfoil if that aerodynamic force is considered to be applied, not at the center of pressure, but at the aerodynamic center of the airfoil.
An animated illustration of the two motions which combine into a Dutch roll Dutch roll damping technique, scanned from U.S. Air Force flight manual. Dutch roll is an aircraft motion consisting of an out-of-phase combination of "tail-wagging" (yaw) and rocking from side to side (roll).