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The way the center of pressure moves as lift coefficient changes makes it difficult to use the center of pressure in the mathematical analysis of longitudinal static stability of an aircraft. For this reason, it is much simpler to use the aerodynamic center when carrying out a mathematical analysis.
The aerodynamic center is the point at which the pitching moment coefficient for the airfoil does not vary with lift coefficient (i.e. angle of attack), making analysis simpler. [ 1 ] d C m d C L = 0 {\displaystyle {dC_{m} \over dC_{L}}=0} where C L {\displaystyle C_{L}} is the aircraft lift coefficient .
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.
For a tailless aircraft, the neutral point coincides with the aerodynamic center, and so for such aircraft to have longitudinal static stability, the center of gravity must lie ahead of the aerodynamic center. [13] For missiles with symmetric airfoils, the neutral point and the center of pressure are coincident and the term neutral point is not ...
When an airfoil moves relative to the air, it generates an aerodynamic force determined by the velocity of relative motion, and the angle of attack. This aerodynamic force is commonly resolved into two components, both acting through the center of pressure: [3]: 14 [1]: § 5.3
The center of gravity (CG) of an aircraft is the point over which the aircraft would balance. [1] Its position is calculated after supporting the aircraft on at least two sets of weighing scales or load cells and noting the weight shown on each set of scales or load cells. The center of gravity affects the stability of the aircraft.
Air above the airfoil is pushed toward the center of the low-pressure region, and air below the airfoil is pushed outward from the center of the high-pressure region. According to Newton's second law , a force causes air to accelerate in the direction of the force.
The other two reference frames are body-fixed, with origins moving along with the aircraft, typically at the center of gravity. For an aircraft that is symmetric from right-to-left, the frames can be defined as: Body frame Origin - airplane center of gravity; x b axis - positive out the nose of the aircraft in the plane of symmetry of the aircraft