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Aircraft center of gravity calculations are only performed along a single axis from the zero point of the reference datum that represents the longitudinal axis of the aircraft (to calculate fore-to-aft balance). Some helicopter types utilize lateral CG limits as well as longitudinal limits.
The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of gravity (cg), known as pitch, roll and yaw. These are collectively known as aircraft attitude , often principally relative to the atmospheric frame in normal flight, but also relative to terrain during takeoff or landing ...
= where is the aircraft lift coefficient. The lift and drag forces can be applied at a single point, the center of pressure. However, the location of the center of pressure moves significantly with a change in angle of attack and is thus impractical for aerodynamic analysis.
Most conventional aircraft have positive longitudinal stability, providing the aircraft's center of gravity lies within the approved range. The operating handbook for every airplane specifies a range over which the center of gravity is permitted to move. [8] If the center of gravity is too far aft, the aircraft will be unstable.
The structural weight limits are based on aircraft maximum structural capability and define the envelope for the CG charts (both maximum weight and CG limits). An aircraft's structural weight capability is typically a function of when the aircraft was manufactured, and in some cases, old aircraft can have their structural weight capability ...
The center of mass, usually called the center of gravity or "CG", is the balance point of an aircraft. If suspended at this point and allowed to rotate, a body (aircraft) will be balanced. The front-to-back location of the CG is of primary importance for the general stability of the aircraft, but the vertical location has important effects as well.
The aerodynamic center of an airfoil is usually close to 25% of the chord behind the leading edge of the airfoil. When making tests on a model airfoil, such as in a wind-tunnel, if the force sensor is not aligned with the quarter-chord of the airfoil, but offset by a distance x, the pitching moment about the quarter-chord point, / is given by
The aircraft manufacturer is usually the only source of this comprehensive flight model. The vertical profile is constructed by the FMS during pre-flight. Together with the lateral flight plan, it makes use of the aircraft's starting empty weight, fuel weight, center of gravity, and cruising altitude.